Functionalized d-Glucosamine Derivatives - ACS Publications

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Synthesis and Study of Molecular Assemblies Formed by 4,6-O(2-Phenylethylidene) Functionalized D-Glucosamine Derivatives Anji Chen, Surya B Adhikari, Kellie Mays, and Guijun Wang Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b01592 • Publication Date (Web): 09 Jul 2017 Downloaded from http://pubs.acs.org on July 13, 2017

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Synthesis and Study of Molecular Assemblies Formed by 4,6-O-(2Phenylethylidene) Functionalized D-Glucosamine Derivatives

Anji Chen, Surya B. Adhikari, Kellie Mays, Guijun Wang*

Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USA.

*Corresponding Author:

Guijun Wang, Ph.D., Professor Department of Chemistry and Biochemistry Old Dominion University 4541 Hampton Boulevard Norfolk, VA23529-0126 Email: [email protected] Telephone: (757) 683-3781 Fax: (757) 683-4628

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Abstract Low molecular weight gelators are interesting small molecules with potential applications as advanced materials. Carbohydrate based small molecular gelators are especially useful since they are derived from renewable resources and are more likely to be biocompatible and biodegradable. Various 4,6-benzylidene acetal protected -methyl 2-D-glucosamine derivatives have been found to be effective low molecular weight gelators. In order to understand the influence of the 4,6benzylidene acetal functional group towards molecular self-assembly and to obtain effective molecular gelators, we synthesized and analyzed a new series of D-glucosamine derivatives in which the phenyl group of the acetal is replaced by a benzyl group. The homologation of the acetal protection from aromatic to aliphatic functional groups allows us to probe the effect of increasing structure flexibility towards the molecular self-assembling and gelation. In this study, nine representative amides and nine urea analogs were synthesized and their gelation properties analyzed in a series of organic solvents and aqueous solutions. The resulting amide and urea derivatives are versatile organogelators forming gels in toluene, ethanol, isopropanol, ethylene glycol, and aqueous mixtures of organic solvents. More interestingly, the amide analogs are also effective gelators for pump oil and engine oil. NMR spectroscopy at variable temperatures was used to analyze the molecular assemblies and intermolecular forces. The selected gelators with several drug and dye molecules in DMSO and water were studied for their effectiveness of encapsulation and release of these agents.

Keywords: Glucosamine, amides, ureas, self-assembly, organogelator, hydrogelator, hydrogen bonds, drug delivery.


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Introduction In recent years, the preparation of soft materials using small molecule self-assembly have gained much attention. In particular, the construction of supramolecular gels by low molecular weight gelators (LMWGs) in organic solvents or water is an especially attractive strategy in discovering functional new materials.1-3 The formation of supramolecular gel networks relies on noncovalent forces such as hydrogen bonding, hydrophobic interactions, - stacking, CH- interactions, and van der Walls forces, etc. The structures of LMWGs encompass a broad range of functionalities and many different classes of small molecules.3-6 The molecular gels thus obtained have been shown to have applications in biomedical research and also useful as new materials for environmental applications and for new catalysts.7-13 Because of the broad range of applications, many efforts have been devoted in understanding gelation mechanism and the rational design of new functional supramolecular gelators.14-17 Among the different classes of molecular gelators, carbohydrate based systems are especially interesting due to several factors. These include that carbohydrate starting materials are renewable natural resources and the resulting gels are potentially biocompatible and biodegradable. For example, N-acetyl 2-D-glucosamine can be obtained from natural sources through degradation of chitin from shells of shrimp and other crustaceans. The polymeric glucosamine derivatives chitin and chitosan have found many applications as biocompatible materials.18-21 D-glucose is an abundant hexose which can be obtained from starch and cellulose hydrolysis. D-glucose and other sugar based molecular gelators have shown many applications for different purposes including for biomedical application and as advanced materials for drug delivery, enzyme immobilization, and for environmental applications and oil spill cleaning up.22-30


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Given the importance of low molecular weight organogelators and hydrogelators, we have systematically studied the functionalization of monosaccharides especially D-glucose and Dglucosamine to obtain effective LMWGs.31-35 As shown in Figure 1, previously we have found that various amide and urea derivatives (1 and 2) of 4,6-O-benzylidene--D-methyl-glucopyranoside 3 are effective gelators for several organic solvents and aqueous solutions. We found that introducing a p-methoxyl substituent to the phenyl ring also resulted in a series of effective LMWGs.35 D-glucosamine based small molecule self-assembly will result in supramolecular networks compounds of the aminosugar but the gel materials are reversible due to the non-covalent nature. Due the ease of synthesis of small molecules, many pure materials can be screened and analyzed. From the bottom up approach, we may be able to obtain novel soft materials with desirable properties. In this study, in order to probe the structure influence towards gelation, especially the phenyl group towards gelation and obtain effective LMWGs for potential applications, we synthesized a new headgroup 4 which has a methylene spacer at the 4,6-protective group. This switches aromatic aldehyde to an alkyl aldehyde which may affect the molecular selfassembly and gelation properties. The additional methylene group increases the hydrophobicity slightly from compound 3 (CLogP -0.56) to compound 4 (CLogP -0.18), the acylated products of the headgroup 4 may also result in derivatives with different gelation capacity or compounds that are more effective towards organic solvents. Through the rational design, a new series of LMWGs could be obtained.


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Figure 1. Structures of several glucosamine derivatives.

Results and Discussions

The headgroup 4 was synthesized by a similar method as before using the N-acetyl D-glucosamine as the starting material.34 The headgroup was then used for the synthesis of amides I and ureas II (Scheme 1). For proof of principle studies, only a few representative functional groups were selected for the current study and the selection of the R and R' groups was based on our previous studies. For a comparison purpose between amides and ureas in an effort to probe the effect of addition hydrogen bonding on gelation, the two series of compounds have similar substituents. These include the pentyl, hexyl, heptyl, cyclohexyl, 10-undecynoyl, 6-heptynoyl, phenyl, 4bromomphenyl and naphthyl. Other analogs with similar structures such as terminal halides are expected to have similar gelation properties as the alkyl analogs with comparable chain lengths.


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Scheme 1. Synthesis of amide derivatives I (8-16) and urea analogs II (17-25).

After these compounds were synthesized, their gelation properties in several solvents were tested and the gelation results are shown in Table 1. For clarity purposes, the screening results of these compounds in hexane, THF, and water are not listed in the table. All amides and ureas performed similarly in these solvents, all are insoluble in hexane, water, and soluble in THF at 20 mg/mL 6 ACS Paragon Plus Environment

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concentrations. In general, the amides are more effective for aqueous mixtures and the ureas are more effective gelators for polar organic solvents. For toluene, the amide derivatives performed better than the urea derivatives; five amide derivatives formed gels in toluene, while only three urea derivatives gelled toluene. For alcohols, urea derivatives are more effective gelators than the amides. A majority of the ureas were able to form gels in ethanol, isopropanol and ethylene glycol. And for water/DMSO mixture, water/ethanol mixtures, the amides are more efficient gelators. The hexyl urea 18 and cyclohexyl urea 20 were also able to solidify dichloromethane (DCM) at 0 °C. The cyclohexyl urea 20 and heptyl urea 19 were also able to form gel in THF and water mixture. All urea analogs except the phenyl urea 23, were able to form effective gels in ethylene glycol (EG), and six amide analogs were gelators for EG at higher concentrations than urea analogs. Low molecular weight gelators are also being explored for their environmental applications, so we also analyzed the gelation potentials of these compounds in pump oil and engine oil. What is interesting is that the amides are effective gelators for these tested oils but ureas are not. The amides with aliphatic functional groups of 6-11 carbon chains are effective gelators for both vacuum pump oil and engine oil. It is foreseeable that linear analogs with longer alkyl chains are also likely to be good gelators for oils. Therefore these gelators or their analog may have applications for oil spill recovery. In contrast, none of the ureas were able to form gels in the pump oil and because of this trend the engine oil was not tested. The change of gelation properties in oils between amides and ureas indicated that the intermolecular interactions among urea molecules are probably too strong and not able to form networks with oils. A majority of the gels are opaque or translucent with some of them are transparent, a few representative photos of the gels are shown in Figure 2. Additional images of the gels are shown in supporting information Figure S13.


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Table 1. Gelation properties of the amides (7-16) and ureas (17-25) EGy

H2O: EtOH (2:1)

H2O: DMSO (2:1)

THF: H2O (1:1)

Pump oil

Engine oil

P

G20 t

I

P

S

I

I

S

S

G20 o

P

G10 o

S

S

I

P

P

P

G10 o

I

I

P

G2.5 O

G 6.7 o

S

G10 t

G0 20 O

G0 20 o

G6.7 o

I

G10 o

S

G4.0 O

G 20.0 o

11

S

G10 t

G10 O

S

S

G2.5 t

G2.8 t

S

G2.0 O

12

S

P

S

S

G20 t

G10 o

I

S

G6.7 O

13

S

G20 t

S

S

S

G10 o

G4.0 o

S

G2.5 O

14

S

P

P

S

G5.0 t

G5.0 o

G10 o

S

I

S

S

G20 t

P

S

S

I

I

P

I

S

16

S

S

G020 o

P

S

G3.3 o

G10 t

S

I

S

17

S

P

S

G20 t

G2.2 t

I

I

P

I

N/A

18

G0 20 c

G6.7 t

G010 c

G0 10 c

G2.5 t

I

I

P

I

N/A

19

P

G20 c

G20 t

S

G1.6 t

I

I

G15 o

I

N/A

20

G0 6.7o

I

G10 t

G10 o

G2.2 t

I

G3.3 t

G15 t

I

N/A

21

S

P

G0 20 c

G0 20 c

G6.7 t

G5.0 o

G5.0 t

S

I

N/A

22

S

G20 t

G0 20 c

G0 20 c

G3.3 c

I

G6.7 o

P

I

N/A

23

I

P

I

P

P

I

I

P

I

N/A

I

P

P

P

G5.0 t

I

I

P

I

N/A

I

I

I

I

G2.5 t

I

G3.3 t

P

I

N/A

DCM

Tolue ne

iPrOH

EtOH

7

S

I

S

8

S

G20 t

9

S

10

No

15

24 25

Structures

Br

Br

All compounds were tested starting from 20 mg/mL concentration. G, stable gel at room temperature, the numbers following G are the corresponding minimum gelation concentrations (MGCs) in mg/mL. G0, forming a gel when the vial is cooled in an ice bath. I, insoluble. P, precipitate. S, soluble at ∼20 mg/mL. The letter abbreviations in regular font denote the appearance of the gel: o, opaque gel; t, translucent gel; c, transparent gel; N/A, not tested. 8 ACS Paragon Plus Environment

G 6.7 o G 4.0 o G 2.2 o

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Figure 2. a) A translucent gel formed by compound 11 in DMSO:H2O (v1:2) at 2.8 mg/mL; b) an opaque gel of compound 11 in EtOH:H2O (v 1:2) at 2.5 mg/mL; c) an opaque gel of compound 21 in EtOH:H2O (v 1:2) at 5.0 mg/mL; d) a transparent gel by compound 19 in ethylene glycol at 3.3 mg/mL; e) a transparent gel formed by compound 13 in engine oil at 2.5 mg/mL.

We then analyzed the morphologies of a few representative gels using optical microscopy, these are shown in Figure 3. The gels formed different morphology in different solvents apparently. Compound 11 in DMSO:H2O (v 1:2) gel showed long and soft entangled fibrous network with narrow diameters ( ~0.3 µm or less, Fig. 3a, b). The gel formed by compound 11 in isopropanol formed more straight fibers with lengths well over 500 µm, they appear to be uniform as well with diameters in the range of 1-1.5 µm. The gel formed by the benzamide 14 in EtOH: H2O (v 1:2) at 5.0 mg/mL (Fig. 3e, f) are somewhat shorter fibers in about 100 µm in length and formed bundles of many fibers with similar sizes (widths ~ 0.6-1 µm). The toluene gel formed by hexyl urea compound 18 showed long continuous and entangled fibrous network with narrow and uniform long fibers with average 0.3 µm diameters. And the urea compound 21 in EtOH: H2O (v 1:2) also formed fibrous type of network but with larger diameters, the fibers are also relatively shorter (~200 µm) and wider (~1.2 µm) comparing to the others.


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Figure 3. Optical micrographs of the gels. a, b) Compound 11 in DMSO:H2O (v 1:2) at 2.8 mg/mL; c, d) Compound 11 in isopropanol at 10 mg/mL; e, f) Compound 14 in EtOH: H2O (v 1:2) at 5.0 mg/mL; g) Compound 18 in toluene at 6.7 mg/mL; h) Compound 21 in EtOH: H2O (v 1:2) at 5.0 mg/mL. 10 ACS Paragon Plus Environment

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To analyze the gels’ stability, the gels formed by compounds 11, 12, 19 and 20 were analyzed using a rheometer, the results are shown in Figure 4. Additional rheological experimental results are shown in the supporting information Figures S8-S12. The Gʹ/Gʺ ratio for 11 and 20 are shown in the supporting information Tables S1 and S2. For the oscillation frequency sweep in a range of different frequencies, all tested gels showed that the storage modulus Gʹ is always greater than the loss modulus Gʺ, which indicates that the gels are stable and have elastic properties.36,37 The storage modulus Gʹ describes the elastic properties (solid-like) of the gels and the loss modulus Gʺ describe the viscous properties (liquid-like). The rheological properties showed that the gels are viscoelastic and remained stable when increasing the angular frequency. The DMSO/H2O gel formed by cyclohexyl amide 11 has the largest storage modulus in this class, followed by the cyclohexyl urea 20. At the linear viscoelastic range, the Gʹ/Gʺ ratio for 11 and 20 are similar; about 7.0 at low angular frequency and increased to 15.0 at high frequency. The large ratio indicated that the gel has more solid like feature, when shear frequency is increased the gel become more rigid. The urea gelator 20 has stronger intermolecular interactions and is more rigid comparing to other systems. The EtOH/H2O gel formed by compound 12 and ethylene glycol gel formed by compound 19 are similar in their storage and loss moduli and ratio, both seem to be less rigid gels than the DMSO/H2O gels.


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Figure 4. Rheological properties of the gels formed by compound 11 (DMSO/H2O, v1:2, 4.8 mg/mL), 12 (EtOH/H2O, v1:2, 10.0 mg/mL), 19 (ethylene glycol, 1.6 mg/mL) and 20 (DMSO/H2O, v 1:2, 5.0 mg/mL) under 1% oscillation strain.

In order to rationalize the gelation properties with the structures especially the influence of hydrogen bonding, we studied the 1H NMR spectra at different temperatures for two representative compounds 12 and 21 (Figures 5-7). Analysis of the 1H NMR spectra of compound 12 in CDCl3 at different temperatures can allow us to probe the hydrogen bonding effect of the gelator molecules with themselves in organic solvents. As shown in Figure 6, the amide NH signal shifted to lower frequencies upon increasing temperatures, with a significant amount of upfield shift from 5.85 ppm at 30 °C to 5.78 ppm at 55 °C. This indicates that intermolecular hydrogen bonding between the gelator molecules decreased at higher temperature. No chemical shift change at the 12 ACS Paragon Plus Environment

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4,6-O- acetal signal was observed at different temperatures, while the anomeric proton has a very small downfield shift from 4.67 ppm to 4.68 ppm.

Figure 5. The chemical shift assignment for the protons in the variable temperature study, the labeled chemical shifts ( ppm) are for 30 °C.


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Figure 6. The 1H NMR spectra of compound 12 from 30-55 °C in CDCl3.

The effect of hydrogen bonding in ureas was analyzed using 1H NMR spectroscopy at different temperatures in deuterated DMSO (Figure 7), the two urea signals shifted up field upon heating, which reflects diminished intermolecular hydrogen bonding. The NH attached to the sugar ring has a larger change of chemical shift of 0.07 ppm versus 0.03 ppm for the NH attached to the alkyl chain. The largest change of chemical shift among all protons is the 3-hydroxyl proton, it shifted from 5.09 ppm to 4.93 ppm from 30 °C to 60 °C. This agrees with what we observed before that


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3-OH group plays an important role in forming intermolecular hydrogen bonds. The 4,6 acetal showed very little difference at different temperatures, while the anomeric hydrogen had a downfield shift of 0.03 ppm as what was observed before.38 This reflects the strength of the intramolecular hydrogen bonds between the 2-NH and the anomeric methoxy group, upon heating or reducing concentrations, the intramolecular hydrogen bonding are not affected as much as the intermolecular hydrogen bonds.

Figure 7. The 1H NMR spectra of compound 21 in from 30-60 °C in d6-DMSO.


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As shown in Table 1, six amide derivatives and four urea derivatives formed gels in the DMSO:H2O (v1:2) solution by the traditional heating and sonication method. For potential biological applications, it is more desirable if the concentration of DMSO can be reduced in aqueous solutions. We tested the gelation tendencies for amides 11, 13, 16, and ureas 20, 25 in different combinations of DMSO with water and ethylene glycol with water. The results are shown in Table 2. The best performing compound is the cyclohexyl amide 11, it formed gels at 1:2, 1:4 and 1:6 volume ratios of DMSO and water; the same compound worked for EG:H2O mixtures. For application of the molecular gelators, spontaneous gelation is more desirable for many biologically applications. Therefore we analyzed the spontaneous gelation potential for compound 11 by dissolving a small amount of gelator in DMSO at 37 °C and add water to the solution, this compound can form stable translucent gel in 20% DMSO water mixture. The photograph of the gels are shown in supporting information Figures S14 and S15.

Table 2. Analysis of gelation in DMSO/water and EG/water mixtures at different ratio DMSO:H2O mixture MGC Ratio

Ethylene Glycol:H2O mixture MGC Ratio

11

G 2.9 T

1:6

G 2.9 O

1:6

13

G 4.0 T

1:4

PG 6.7 o

1:2

16

G 4.0 O

1:4

G 6.7 O

1:2

20

G 6.7 T

1:2

N/A

N/A

25

G 6.7 T

1:2

N/A

N/A

Compound

Structures

G: stable gel; PG: partial gel; UG: unstable gel. Gel appearance: o, opaque; c, clear or transparent; t, translucent; N/A, not tested.


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The gel formed by compound 11 in DMSO:H2O (v1:4) was selected for testing sustained release profile of trapped drugs from gel phase to solution phase. Naproxen and chloramphenicol (Figure 8) were selected for the study. The purpose for the characterization is to analyze the ability of the gelator to encapsulate drug molecules in the gel matrix. The drug release was monitored by UV absorption at certain time by transferring the supernatant with pipet to a cuvette, after each measurement the aqueous phase was carefully transferred back to the vial. The gel photos of naproxen release and chloramphenicol release study are shown in Figures S17-S19. The UV spectra of naproxen release from the gel to the water phase at different time and the estimated release% are shown in Figure 9. About 50% naproxen was released from the gel to aqueous phase after 2 h, and after 20 h, almost all naproxen was released to the aqueous phase.

Figure 8. Structures of the drug molecules


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Figure 9. Release of naproxen (a,b) and chloramphenicol (c,d) from gel to aqueous phase. a) UV spectra of the naproxen, the gel is formed by 2 mg of compound 11 in 0.5 mL DMSO:H2O (v1:4) with 0.5 mg of naproxen, naproxen control was prepared by dissolving 0.5 mg naproxen in 3 mL of water; b) Absorbance at 330 nm at different times versus the standard was used to calculate the % release. c) UV spectra of chloramphenicol at different times, d) % release of chloramphenicol from gel to solution phase estimated by taking the ratio of absorbance at 278 nm with chloramphenicol standard. The gel was formed by 2 mg of compound 11 in 0.5 mL DMSO:H2O (v1:4) with 0.25 mg of chloramphenicol. Chloramphenicol control was prepared by dissolving 0.25 mg chloramphenicol in 3 mL of water.


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In contrast, chloramphenicol seems to be absorbed on the gel matrix more strongly (Figure 9), about 50% drug was diffused to aqueous phase after 8 h, and in 20 h, only 60% trapped chloramphenicol was released from the gel to solution phase. The difference of the release profile of the two drugs could be partially due to the solubility difference in water. The gels were intact for both samples after the 20 h period of experiment (Figure S19). The naproxen gels seem to have lost some volume perhaps due to the better water solubility of the drug, when removing water each time some part of the co-gel were removed. The chloramphenicol co-gel remained the same after the 20 h of experiment. Therefore the gelator compound may be useful in encapsulation and sustained release of chloramphenicol, it is reasonable to expect that the gelator could be used for other neutral small molecular drugs. Also the sustained release could be controlled by changing the gelator concentration and gel strength.

In order to understand how the gels may interact with cationic compounds, next we analyzed the absorption of toluidine blue dye from aqueous to gel phase through diffusion or absorption. The gel formed by compound 16 in DMSO:H2O mixture (v1:4) at 4 mg/mL was used for the study. Compound 16 contains a naphthyl functional group which may allow more π–π stacking interaction with the dye’s aryl systems and allow the dye to be trapped within the gel matrix more effectively. Toluidine blue dye has distinct UV absorptions at long wavelength region which doesn’t interfere with the gelators and typical drugs. Adsorption of toluidine blue from aqueous solution to the hydrogel at different time intervals was monitored by UV-Vis spectroscopy and results are shown in Figure 10. Photographs were taken at different time course and are included in supporting information (Figure S20). Toluidine blue is known to form dimer aggregates in aqueous solutions, the dimer form is corresponding to the absorption max at 590 nm and the


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monomer typically has max at 626 nm.39 As shown in Figure 10, before adding to the gel matrix, toluidine blue forms dimer predominantly which gives the absorption max at 590 nm, and a small amount of the dye exists in the monomer form with max at 626 nm as a shoulder peak. As the dye starts diffusing into the gel matrix, the dimer form diminished more rapidly than the monomer form, and after 64 h, the major absorption in the aqueous phase is the monomer form at 626 nm. This indicates that the gel matrix is able to stabilize the monomer or breaking down the dimer complex of toluidine blue. This implies that the gel matrix may be able to interact with the cationic dyes by stabilizing the monomer of toluidine blue, which may have certain applications to separate different substrates using the gels.

3 2.5

0 h 8 h

Absorbance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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2

16 h 24 h

1.5

32 h 48 h

1

64 h

0.5 0 400

500

600

Wavelength (nm)

700

800

Figure 10. UV-Vis spectra of toluidine blue solution above the gel of compound 16 after indicated hours. The gel was formed by 8 mg of compound 16 in with 2 mL of DMSO:H2O mixture (v1:4), 2 mL toluidine dye solution (0.10 mM) was deposited on top of the gel.


Langmuir

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Conclusions We have rationally designed and synthesized a new series of D-glucosamine derivatives containing 4,6-O-(2-phenylethylidene) protective group as effective low molecular weight gelators. The amide analogs are effective organogelators for toluene, isopropanol and ethylene glycol, they are also effective for forming gels in aqueous mixtures of DMSO or ethanol. In contrast, the corresponding urea analogs are more effective for organic solvents including dichloromethane, toluene, ethanol, isopropanol and ethylene glycol, but not very effective in aqueous mixtures of DMSO or ethanol. Interestingly, almost all of the synthesized amide and urea derivatives are effective gelator for ethylene glycol. The amide analogs are also effective gelators for pump oil and engine oils, while the urea analogs are not effective gelators for oils and they also showed diminished gelation tendencies in aqueous solutions. The insertion of a methylene group at the 4,6-O-benzylidene acetal protective group increases the hydrophobicity of the derivatives. Therefore, the analogs are expected to be more effective in trapping organic solvents; polar substituents can be introduced to the molecules to obtain other molecular gelators for water or aqueous solutions in the future. In summary, the insertion of methylene group between phenyl and the hydroxyl groups didn’t affect the gelation properties, most analogs are able to form stable gels in at least one tested solvents. 1H NMR spectroscopy at variable temperature shows the importance of hydrogen bonding for both amide and urea analogs. The compounds that are effective gelators in DMSO and water mixtures were studied for their potential in encapsulating naproxen and chloramphenicol drug molecules. The results obtained here are expected to be useful models for drug delivery using gel matrix formed by molecular gelators.


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Langmuir

Experimental section: General method and materials: Reagents and solvents were used as they were received from the suppliers. All purification was conducted by flash chromatography using 230-400 mesh silica gel obtained from Natland International Corporation, unless otherwise noted. The solvent systems used for chromatography are all in volume ratio. The solvent mixtures for all gelation test are also in volume ratios. NMR analysis was conducted using a 400 MHz Bruker NMR spectrometer. Melting point measurements were carried out using a Stuart automatic melting point apparatus SMP40. Rheology measurement was done using a HR-2 Discovery Hybrid Rheometer from TA instrument and a 25 mm Peltier Plate.

General method for characterizations of molecular assemblies

Gelation testing: About 2 mg of dried compound was placed in a 1 dram glass vial and the corresponding solvent was added to obtain a concentration of 20 mg/mL. The mixture was then heated until the solids were fully dissolved, sometimes sonication was needed to dissolve the sample, then the solution was allowed to cool to room temperature and let stand for 15 minutes. After this period, if the sample is clear, this is recorded as soluble, if solid reappeared, this is recorded as precipitate; if the sample formed a gel, then the via is inverted and if there is no solvent flowing this indicated that a stable gel is formed, otherwise this is recorded as unstable gel. The stable gel was then serial diluted till the minimum gelation concentration, which is the concentration prior to unstable gelation, is obtained. Additional gel photos are included in Figure S13.


Langmuir

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For testing different aqueous solutions: 2 mg of each tested compound (11, 13, 16, 20, and 25) was weighed and transferred to a 1 dram vial following by adding 0.1 mL of DMSO/Ethylene glycol. The mixture was then heated until the solids were fully dissolved. To this mixture 0.2 mL of water was added, serial dilution was then performed. The vial was inverted to prove that a stable gel was formed. Some photos of stable gels at maximum amount of water versus organic solvents are shown in Figure S14.

Spontaneous gelation test: 2 mg of compound 11 was weighed and transferred to a 1 dram vial followed by adding 0.1 mL of DMSO. Compound was gradually dissolved when the mixture was immersed in 37 °C water bath. A 1 mL syringe containing 0.4 mL of water at pH 7 with a needle was used to transfer water by slow injection of water through needles to the bottom of the vial during a 2 minutes injection time. After completely adding 0.4 mL of water, the syringe was removed gently from the mixture. The mixture was left at the 37 °C water bath for 10 minutes before it was removed and let standing at rt for 1 hour. Then the vial was inverted and if there is no solvent flowing this indicated that a stable spontaneous gel is formed. Some photos of stable gels are shown in Figure S15.

Optical microscopy studies: A small amount of the gels was placed on a clean glass slide and this was observed under an Olympus BX60M optical microscope and the Olympus DP73-1-51 high performance 17MP digital camera with pixel shifting and Peltier cooled. The imaging software for image capturing is CellSens 1.11. For aqueous DMSO solvent, the gel was left air dry for a day or so, for other solvents the slides were observed directly.


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Langmuir

Rheological analyses: Rheological behavior of gel was investigated by HR-2 Discovery Hybrid Rheometer from TA instrument with the TRIOS software. A sample (approximately 1 mL of the gel) was placed on the steel plate of the rheometer. The cone geometry is 25-mm peltier plate and with a gap of 100 µm. The experimental temperature was 25 °C, the sample was subjected to amplitude sweep for oscillation strain from 0.125% to 10%. A frequency sweep was then performed for the sample in the range of 0.1 to 100.0 rad/s for angular frequency. The results were expressed as the storage modules (G′) and loss modules (G″) as a function of the angular frequency.

Naproxen trapping and release: A gel was prepared in a 1 dram via using 2 mg of compound 11 and 0.5 mg of naproxen sodium and 0.5 mL DMSO:H2O (v1:4), after a stable gel formed and the gel was left undisturbed for 2 hours, 3 mL of water at pH 7 was added to the top of the gel carefully. Naproxen release from the gel was monitored by UV absorption at certain time by transferring the supernatant with pipet to a cuvette, after each measurement the aqueous phase was carefully transferred back to the vial and placed on top of the gel again till the next measurement. The UV spectra of the pure naproxen and pure gelator in the test solvent system were also recorded.

Chloramphenicol trapping and release: The gelator-drug co-gel was prepared by using 2 mg of compound 11 in 0.5 mL DMSO:H2O (v1:4) with 0.25 mg of chloramphenicol. Chloramphenicol control was prepared by dissolving 0.25 mg chloramphenicol in 3 mL of water. The experiment was performed similarly to the naproxen release study. Additional figures are included in the supporting information Figures S16-S19.


Langmuir

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Dye diffusion and absorption studies: Toluidine blue dye was selected for the diffusion study with the gel formed by compound 16. A gel was prepared in a 1 dram vial using 8 mg of compound 16 in 2 mL of DMSO:H2O mixture (v1:4) the concentration of the gelator is 4 mg/mL. After a stable gel was formed and the gel was left at room temperature for 2 hours, 2 mL of toluidine blue aqueous solution (0.1 mM) was added dropwise onto the top of the gel. Adsorption of toluidine blue from aqueous solution to the gel at different time intervals was monitored by UV-Vis spectroscopy and results are shown in Figure 10. Photographs were taken at different time course and are shown in Figure S20.

Synthesis and characterization data of headgroup 4, amides 7-16, and ureas 17-25. Synthesis of the 4,6-O-(2-phenylethylidene) protected headgroup 4 To a 50 mL round bottom flask, compound 6 (α: β = 9:1)34 (2.00 g, 8.50 mmol, 1 equiv), phenyl acetaldehyde dimethyl acetal (1.83 mL, 11.05 mmol, 1.3 equiv), PTSA monohydrate (162 mg, 0.85 mmol, 0.1 equiv) and 10 mL anhydrous DMF were added in the given order. The resulting mixture was stirred at 70 °C for 6 hours under N2 atmosphere. Then the reaction mixture was neutralized by adding NaHCO3 (143 mg, 1.70 mmol, 0.2 equiv) and stirring was continued at rt for 30 minutes. After removing DMF under reduced pressure, workup was performed using dichloromethane (DCM, 30 mL x 3) and water (10 mL). The combined organic layer was dried over Na2SO4 (anhydrous), filtered and concentrated to afford crude product. The crude product was recrystallized using absolute EtOH/Hexanes mixture to afford 1.80 g (5.34 mmol, 63%) white solid as part of the pure product. The mother liquor residue was concentrated and purified by flash chromatography on silica gel using DCM to 5% MeOH/DCM to give 0.55 g (1.63 mmol, 19%)


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Langmuir

pure compound 7 (0.55 g, 1.63 mmol, 19%), Rf = 0.5 in 5% MeOH/DCM. The final yield of compound 7 is 82% (2.35 g, 6.97 mmol), mp 245.0-247.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.317.20 (m, 5H, Ar-H), 5.88 (d, J = 8.4 Hz, 1H, -NH-), 4.77 (dd, J = 6.5, 3.8 Hz, 1H, Ph-CH2-CH-), 4.67 (d, J = 3.8 Hz, 1H, H-1), 4.20-4.08 (m, 2H, H-2, H-6a), 3.84 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.69-3.60 (m, 1H. H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.39-3.33 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.8 Hz, 1H, Ph-CHa-CH-), 2.93 (dd, J = 14.2, 6.5 Hz, 1H, Ph-CHb-CH-), 2.06 (s, 3H, Ac); 13C NMR (100 MHz, CDCl3) δ 171.7, 136.1, 129.7, 128.3, 126.6, 102.8 (Ph-CH2-CH-), 98.7 (C-1), 81.6 (C-4), 71.1 (C-3), 68.4 (C-6), 62.3 (C-5), 55.2 (-OCH3), 54.2 (C-2), 40.9 (PhCH2-CH-), 23.3 (Ac); LC-MS m/z calcd for C17H24NO6 [M + H]+ 338.2 found 338.1.

Deacetylation reaction was performed either in thermal or microwave condition using KOH in ethanol under refluxing conditions similarly as previous reported to afford compound 4 from compound 7 (500 mg, 1.48 mmol, 1 equiv) as a while solid in quantitative yield (437 mg, 1.48 mmol). mp 128.0-130.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.31-7.20 (m, 5H, Ar-H), 4.75 (dd, J = 6.2, 4.1 Hz, 1H, Ph-CH2-CH-), 4.64 (d, J = 3.1 Hz, 1H, H-1), 4.10 (dd, J = 10.2, 4.9 Hz, 1H, H6a), 3.71-3.63 (m, 2H, H-5, H-3), 3.47 (dd ~ t, J = 10.4 Hz, 1H, H-6b), 3.38 (s, 3H, -OCH3), 3.26 (dd ~ t, J = 9.3 Hz, 1H, H-4), 3.03 (dd, J = 14.2, 4.1 Hz, 1H, Ph-CHa-CH-), 2.94 (dd, J = 14.2, 6.2 Hz, 1H, Ph-CHb-CH-), 2.75 (s, 1H, H-2), 2.03 (s, 3H, -OH, -NH2); 13C NMR (100 MHz, CDCl3) δ 136.2, 129.6, 128.3, 126.6, 102.7 (Ph-CH2-CH-), 101.2 (C-1), 81.5 (C-4), 71.6 (C-3), 68.7 (C6), 62.6 (C-5), 56.7 (C-2), 55.4 (-OCH3), 40.9 (Ph-CH2-CH); LC-MS m/z calcd for C15H22NO5 [M + H]+ 296.1 found 296.1.


Langmuir

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General procedure for the amide derivatives 8-16 The corresponding acyl chloride (or made from carboxylic acid reacting with oxalyl chloride) (1.2 equiv) was added dropwise to a solution composed of compound 4 (75 mg, 0.254mmol, 1.0 equiv), DIEA (2.0 equiv) and anhydrous THF at 0 °C in an ice bath. The resulting mixture was stirred at 0 °C or brought to rt for a few hours (4 to 7 h). THF was removed using the rotavap. Workup was done using DCM and water or 5% NaHCO3 (aq.). The combined organic layer was dried over Na2SO4 (anhydrous), filtered and concentrated to give the crude, which was purified by column chromatography to afford corresponding amide as the desired product. The detailed procedures for compounds 8 and 12 are given, the others only the characterization data are included since they were synthesized by the same procedure.

Synthesis of pentyl amide derivative 8 To a scintillation vial, valeric acid (0.034 mL, 0.305 mmol, 1.2 equiv), 3 mL DCM (anhydrous), 1 drop DMF (anhydrous) were added in the given order. The resulting mixture was stirred at 0 °C for 10 minutes followed by adding oxalyl chloride dropwise (0.026 mL, 0.305 mmol, 1.2 equiv) and then was stirred at rt for 4 hours. The above prepared acyl chloride and was added at 0 °C dropwise to another solution containing compound 4 (75 mg, 0.254 mmol, 1 equiv), DIEA (0.044 mL, 0.280 mmol, 1.1 equiv) in 3 mL THF (anhydrous). Reaction mixture was stirred at rt for 7 hours. THF was removed using the rotavap. Workup was done using DCM (10 mL x 3)/water (10 mL). The combined organic layer was dried over Na2SO4 (anhydrous), filtered and concentrated to give the crude, which was purified by column chromatography using eluent from pure DCM to 5% MeOH/DCM to afford off-white solid (88 mg, 85%) as the desired product (Rf = 0.5 in 5%


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Langmuir

MeOH/DCM); mp 206.0-208.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.31-7.20 (m, 5H), 5.86 (d, J = 8.5 Hz, 1H, -NH-), 4.77 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.67 (d, J = 3.9 Hz, 1H, H-1), 4.20-4.07 (m, 2H, H-2, H-6a), 3.83 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.68-3.60 (m, 1H. H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.40-3.34 (m, 4H, -OCH3, H-4), 3.23 (s, 1H, -OH), 3.05 (dd, J = 14.2, 3.8 Hz, 1H, Ph-CHa-CH-), 2.93 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.25 (t, J = 7.6 Hz, 2H, CH2-C=O), 1.70-1.58 (m, 2H), 1.43-1.31 (m, 2H), 0.93 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 174.9, 136.1, 129.7, 128.3, 126.6, 102.8, 98.7, 81.6, 71.2, 68.4, 62.3, 55.2, 54.1, 40.9, 36.4, 27.6, 22.3, 13.7; LC-MS m/z calcd for C20H30NO6 [M + H]+ 380.2, found 380.2.

Synthesis of hexyl amide derivative 9 The crude product was purified by column chromatography using hexane:acetone:DCM (2:1:1) to afford the compound 9 as a white solid (85 mg, 85%), Rf = 0.5 in hexane:acetone:DCM = 2:1:1, mp 203.0-205.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.33-7.19 (m, 5H), 5.85 (d, J = 8.4 Hz, 1H, NH-), 4.77 (dd, J = 6.4, 3.7 Hz, 1H, Ph-CH2-CH-), 4.66 (d, J = 3.8 Hz, 1H, H-1), 4.20-4.07 (m, 2H, H-2, H-6a), 3.82 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.69-3.61 (m, 1H, H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.41-3.33 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.7 Hz, 1H, Ph-CHa-CH-), 2.93 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.25 (t, J = 7.6 Hz, 2H, -CH2-C=O), 1.71-1.59 (m, 2H), 1.39-1.25 (m, 4H), 0.90 (t, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 174.9, 136.1, 129.7, 128.3, 126.6, 102.8, 98.7, 81.6, 71.2, 68.4, 62.3, 55.2, 54.1, 40.9, 36.6, 31.3, 25.3, 22.3, 13.9; LCMS m/z calcd for C21H32NO6 [M + H]+ 394.2, found 394.2.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Synthesis of heptyl amide derivative 10 The crude product was purified by flash chromatography using hexane:acetone:DCM (2:1:1) to afford the desired product as a white solid (88 mg, 85%), Rf = 0.5 in hexane:acetone:DCM = 2:1:1; mp 195.0-197.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.32-7.20 (m, 5H), 5.86 (d, J = 8.5 Hz, 1H, NH-), 4.77 (dd, J = 6.5, 3.7 Hz, 1H, Ph-CH2-CH-), 4.67 (d, J = 3.9 Hz, 1H, H-1), 4.19-4.08 (m, 2H, H-2, H-6a), 3.83 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.69-3.61 (m, 1H. H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.40-3.34 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.7 Hz, 1H, Ph-CHa-CH-), 2.93 (dd, J = 14.2, 6.5 Hz, 1H, Ph-CHb-CH-), 2.25 (t, J = 7.7 Hz, 2H, -CH2-C=O), 1.69-1.58 (m, 2H), 1.39-1.24 (m, 6H), 0.89 (t, J = 6.9 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 174.9, 136.1, 129.7, 128.3, 126.6, 102.8, 98.7, 81.6, 71.2, 68.4, 62.3, 55.2, 54.1, 40.9, 36.6, 31.5, 28.8, 25.5, 22.5, 14.0; LC-MS m/z calcd for C22H34NO6 [M + H]+ 408.2, found 408.2.

Synthesis of cyclohexyl amide derivative 11

The crude was purified by flash chromatography using solvent system from pure DCM to 5% MeOH/DCM to afford the pure product 11 as a white solid (95 mg, 92%), Rf = 0.5 in 5% MeOH/DCM; mp 207.0-209.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.32-7.19 (m, 5H), 5.88 (d, J = 8.4 Hz, 1H, -NH-), 4.77 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.65 (d, J = 3.9 Hz, 1H, H-1), 4.17-4.07 (m, 2H, H-2, H-6a), 3.82 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.68-3.60 (m, 1H. H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.40-3.34 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.8 Hz, 1H, PhCHa-CH-), 2.93 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.20-2.11 (m, 1H, O=C-CH-), 1.94-1.74 (m, 4H), 1.72-1.64 (m, 1H), 1.52-1.39 (m, 2H), 1.35-1.16 (m, 3H); 13C NMR (100 MHz, CDCl3)


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Langmuir

δ 178.0, 136.1, 129.7, 128.2, 126.6, 102.8, 98.7, 81.6, 71.4, 68.4, 62.3, 55.2, 54.1, 45.3, 40.9, 29.6, 29.5, 25.64, 25.61, 25.59; LC-MS m/z calcd for C22H32NO6 [M + H]+ 406.2, found 406.2.

Synthesis of 6-heptynyl amide derivative 12 To a scintillation vial, 6-heptynoic acid (0.036 g, 0.305 mmol, 1.1 equiv), 3 mL DCM (anhydrous), 1 drop DMF (anhydrous) were added in the given order. The resulting mixture was stirred at 0°C for 10 minutes followed by adding oxalyl chloride dropwise (0.078 mL, 0.508 mmol, 2 equiv) and then was stirred at room temperature for 15 hours. The above prepared acyl chloride and was added at 0 °C dropwise to another solution containing compound 4 (75 mg, 0.254 mmol, 1 equiv), DIEA (0.044 mL, 0.280 mmol, 1.1 equiv) in 3 mL THF (anhydrous). Reaction mixture was stirred at 0 °C for 4 hours. THF was removed using the rotavap. Workup was done using DCM (10 mL x 3)/5% NaHCO3 (aq. 5 mL). The combined organic layer was dried over Na2SO4 (anhydrous), filtered and concentrated to give the crude, which was purified by flash chromatography using solvent system from pure DCM to 5% MeOH/DCM to afford the pure product 12 as an off-white solid (85 mg, 83%), Rf = 0.5 in 5% MeOH/DCM; mp 179.0-181.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.32-7.19 (m, 5H), 5.86 (d, J = 8.6 Hz, 1H, -NH-), 4.77 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.66 (d, J = 3.7 Hz, 1H, H-1), 4.20-4.08 (m, 2H, H-2, H-6a), 3.83 (dd ~t, J = 9.6 Hz, 1H, H-3), 3.69-3.61 (m, 1H. H-5), 3.49 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.40-3.33 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.8 Hz, 1H, Ph-CHa-CH-), 2.93 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.29 (t, J = 7.2 Hz, 2H), 2.22 (dt, J = 7.0, 2.6 Hz, 2H), 1.96 (t, J = 2.6 Hz, 1H), 1.83-1.73 (m, 2H), 1.63-1.53 (m ,2H); 13C NMR (100 MHz, CDCl3) δ 174.3, 136.1, 129.7, 128.3, 126.6, 102.8, 98.7, 84.0, 81.6, 71.2, 68.7, 68.4, 62.3, 55.2, 54.1, 40.9, 36.0, 27.8, 24.6, 18.2; LC-MS m/z calcd for C22H30NO6 [M + H]+ 404.2, found 404.2. 30 ACS Paragon Plus Environment

Langmuir

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Synthesis of 10-undecynyl amide derivative 13 10-undecynoic acid (0.051 g, 0.305 mmol, 1.2 equiv) was used to prepare the corresponding acid chloride. The crude was purified by flash chromatography using solvent system from pure DCM to 5% MeOH/DCM to afford the pure product 13 as a white solid (95 mg, 81%), Rf = 0.7 in 5% MeOH/DCM; mp 167.0-169.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.31-7.19 (m, 5H), 5.85 (d, J = 8.5 Hz, 1H, -NH-), 4.77 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.66 (d, J = 3.8 Hz, 1H, H-1), 4.19-4.08 (m, 2H, H-2, H-6a), 3.83 (dd ~t, J = 9.6 Hz, 1H, H-3), 3.68-3.60 (m, 1H. H-5), 3.48 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.40-3.34 (m, 4H, -OCH3, H-4), 3.05 (dd, J = 14.2, 3.8 Hz, 1H, PhCHa-CH-), 2.93 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.24 (t, J = 7.6 Hz, 2H), 2.18 (dt, J = 7.0, 2.6 Hz, 2H), 1.93 (t, J = 2.6 Hz, 1H), 1.71-1.59 (m, 2H), 1.56-1.48 (m ,2H), 1.43-1.26 (m, 8H); 13

C NMR (100 MHz, CDCl3) δ 174.9, 136.1, 129.7, 128.3, 126.6, 102.8, 98.7, 84.7, 81.6, 71.3,

68.4, 68.1, 62.3, 55.2, 54.1, 40.9, 36.6, 29.14, 29.06, 28.9, 28.6, 28.4, 25.5, 18.4; LC-MS m/z calcd for C26H38NO6 [M + H]+ 460.3, found 460.2.

Synthesis of benzamide derivative 14 The crude was purified by flash chromatography using solvent system hexane:acetone:DCM (2:1:1) to afford the pure product 14 as a white solid (88 mg, 82%), Rf = 0.5 in hexane:acetone:DCM=2:1:1. mp 205.0-207.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.83-7.73 (m, 2H), 7.57-7.51 (m, 1H), 7.50-7.43 (m, 2H), 7.32-7.21 (m, 5H), 6.52 (d, J = 8.5 Hz, 1H, -NH-), 4.82-4.78 (m, 2H, Ph-CH2-CH-, H-1), 4.42-4.35 (m, 1H, H-2), 4.14 (dd, J = 10.3, 4.9 Hz, 1H, H6a), 3.96 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.75-3.66 (m, 1H. H-5), 3.52 (dd ~ t, J = 10.3 Hz, 1H, H6b), 3.48-3.39 (m, 4H, -OCH3, H-4), 3.07 (dd, J = 14.2, 3.8 Hz, 1H, Ph-CHa-CH-), 2.95 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-); 13C NMR (100 MHz, CDCl3) δ 168.7, 136.1, 133.6, 132.0, 129.7,


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Langmuir

128.7, 128.3, 127.2. 126.6, 102.8, 98.8, 81.6, 71.3, 68.4, 62.4, 55.3, 54.6, 40.9; LC-MS m/z calcd for C22H26NO6 [M + H]+ 400.2, found 400.2.

Synthesis of 4-bromobenzamide derivative 15 The crude was purified by flash chromatography using solvent system from pure DCM to 5% MeOH/DCM to afford the pure product 15 as a white solid (97 mg, 80%), Rf = 0.6 in 5% MeOH/DCM; mp 252.0-254.0 °C. 1H NMR (400 MHz, CDCl3) δ 7.69-7.65 (m, 2H), 7.62-7.57 (m, 2H), 7.32-7.21 (m, 5H), 6.44 (d, J = 8.6 Hz, 1H, -NH-), 4.82-4.76 (m, 2H, Ph-CH2-CH-, H-1), 4.40-4.33 (m, 1H, H-2), 4.14 (dd, J = 10.3, 4.9 Hz, 1H, H-6a), 3.95 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.74-3.66 (m, 1H. H-5), 3.52 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.46-3.38 (m, 4H, -OCH3, H-4), 3.07 (dd, J = 14.2, 4.0 Hz, 1H, Ph-CHa-CH-), 2.95 (dd, J = 14.2, 6.3 Hz, 1H, Ph-CHb-CH-); 13C NMR (100 MHz, CDCl3) δ 167.6, 136.1, 132.5, 131.9, 129.7, 128.8, 128.3, 126.8. 126.7, 102.8, 98.7, 81.6, 71.0, 68.4, 62.4, 55.3, 54.5, 40.9; LC-MS m/z calcd for C22H25BrNO6 [M + H]+ 478.1, found 478.1.

Synthesis of 1-naphthyl amide derivative 16 The crude was purified by flash chromatography using solvent system from pure DCM to 5% MeOH/DCM to afford the pure product 16 as a white solid (105 mg, 92%), Rf = 0.5 in 5% MeOH/DCM; mp 142.0-144.0 °C. 1H NMR (400 MHz, CDCl3) δ 8.36-8.31 (m, 1H), 7.97-7.85 (m, 2H), 7.69-7.63 (m, 1H), 7.60-7.44 (m, 3H), 7.34-7.20 (m, 5H), 6.39 (d, J = 8.8 Hz, 1H, -NH), 4.87 (d, J = 3.8 Hz, 1H, H-1), 4.81 (dd, J = 6.2, 4.1 Hz, 1H, Ph-CH2-CH-), 4.53-4.45 (m, 1H, H2), 4.15 (dd, J = 10.3, 4.9 Hz, 1H, H-6a), 3.98 (dd ~ t, J = 9.6 Hz, 1H, H-3), 3.74-3.67 (m, 1H. H5), 3.54 (dd ~ t, J = 10.3 Hz, 1H, H-6b), 3.45 (dd ~ t, J = 9.3 Hz, 1H, H-4), 3.39 (s, 3H, -OCH3),


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 43

3.07 (dd, J = 14.2, 4.1 Hz, 1H, Ph-CHa-CH-), 2.95 (dd, J = 14.2, 6.2 Hz, 1H, Ph-CHb-CH-); 13C NMR (100 MHz, CDCl3) δ 170.8, 136.1, 133.74, 133.69, 131.0, 130.1, 129.7, 128.4, 128.3, 127.4, 126.6, 126.5, 125.3, 125.2, 124.7, 102.8, 98.8, 81.7, 71.1, 68.4, 62.5, 55.3, 54.6, 40.9; LC-MS m/z calcd for C26H28NO6 [M + H]+ 450.2, found 450.2.

General procedure for the urea derivatives 17-25 Compound 4 (75 mg, 0.254 mmol, 1 equiv) was dissolved in anhydrous THF in a scintillation vial. Then corresponding isocyanate (1 equiv from commercial starting material or prepared in situ from the corresponding carboxylic acid via Curtius rearrangement) was added to the reaction mixture. The resulting mixture was stirred at rt. THF was removed using the rotavap to afford the crude. If the crude was checked by 1H NMR to confirm that it doesn’t need column purification, the crude product was typically dried further under vacuum overnight to remove trace amount of solvent residue. If crude was not clean, the crude was chromatographed to give corresponding urea as the desired product. The detailed procedures for compounds 17 and 21 are given, only the characterization data are included for the others since they were synthesized by the same procedures.

Synthesis of pentyl urea derivative 17 Compound 4 (75 mg, 0.254 mmol, 1 equiv) was dissolved in 3 mL THF (anhydrous) in a scintillation vial. Then pentyl isocyanate (0.041 mL, 0.254 mmol, 1 equiv) was added to the reaction mixture. The resulting mixture was stirred at rt for 8 hours. THF was removed using the rotavap to afford white solid (87 mg, 82%) as the desired product, mp 217.0-219.0 °C. 1H NMR (400 MHz, d6-DMSO) δ 7.32-7.18 (m, 5H), 6.04 (t, J = 5.6 Hz, 1H, -NH-CH2-), 5.72 (d, J = 8.5 Hz, 1H, -NH-CH-), 5.09 (d, J = 6.0 Hz, 1H, -OH), 4.79 (dd, J = 6.3, 4.0 Hz, 1H, Ph-CH2-CH-), 33 ACS Paragon Plus Environment

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

4.56 (d, J = 3.6 Hz, 1H, H-1), 4.03-3.94 (m, 1H, H-6a), 3.66-3.58 (m ,1H, H-2), 3.50-3.40 (m, 3H, H-6b, H-3, H-4), 3.29-3.23 (m, 4H, -OCH3, H-5), 3.00-2.89 (m, 3H, Ph-CHa-CH-, -NH-CH2-), 2.81 (dd, J = 14.2, 6.3 Hz, 1H, Ph-CHb-CH-), 1.40-1.18 (m, 6H), 0.86 (t, J = 7.0 Hz, 3H); 13C NMR (100 MHz, d6-DMSO) δ 157.9, 136.3, 129.5, 128.0, 126.2, 101.7, 99.4, 81.5, 68.6, 67.5, 62.5, 54.6, 40.3, 39.1, 29.6, 28.6, 21.8, 13.9; LC-MS m/z calcd for C21H33N2O6 [M + H]+ 409.2, found 409.2.

Synthesis of hexyl urea derivative 18 The

crude

product

was

purified

by

flash

chromatography

using

solvent

system

hexane:DCM:acetone (2:1:1) to afford the pure product as a white solid (89 mg, 83%), Rf = 0.5 in hexane: DCM: acetone = 2:1:1, mp 213.0-215.0 °C. 1H NMR (400 MHz, d6-DMSO) δ 7.30-7.18 (m, 5H), 6.04 (t, J = 5.6 Hz, 1H, -NH-CH2-), 5.72 (d, J = 8.5 Hz, 1H, -NH-CH-), 5.08 (d, J = 6.0 Hz, 1H, -OH), 4.79 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.56 (d, J = 3.6 Hz, 1H, H-1), 4.033.95 (m, 1H, H-6a), 3.65-3.58 (m ,1H, H-2), 3.49-3.40 (m, 3H, H-6b, H-3, H-4), 3.28-3.24 (m, 4H, -OCH3, H-5), 3.00-2.90 (m, 3H, Ph-CHa-CH-, -NH-CH2-), 2.81 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHbCH-), 1.39-1.21 (m, 8H), 0.86 (t, J = 6.7 Hz, 3H); 13C NMR (100 MHz, d6-DMSO) δ 157.9, 136.3, 129.5, 128.0, 126.2, 101.7, 99.4, 81.5, 68.6, 67.5, 62.5, 54.6, 40.3, 39.2, 31.0, 29.8, 26.0, 22.0, 13.9; LC-MS m/z calcd for C22H35N2O6 [M + H]+ 423.2, found 423.2.

Synthesis of heptyl urea derivative 19 Compound 4 (75 mg, 0.254 mmol, 1 equiv) and heptyl isocyanate (0.041 mL, 0.254 mmol, 1 equiv) were used as the starting materials. After 6 h reaction and removal of all solvent the desired product 19 was obtained as a white solid (90 mg, 81%), mp 216.0-218.0 °C. THF was removed using the


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

rotavap to afford white solid (90 mg, 81%) as the desired product. mp 216.0-218.0 °C. 1H NMR (400 MHz, d6-DMSO) δ 7.30-7.18 (m, 5H), 6.04 (t, J = 5.6 Hz, 1H, -NH-CH2-), 5.72 (d, J = 8.5 Hz, 1H, -NH-CH-), 5.09 (s, 1H, -OH), 4.79 (dd, J = 6.4, 3.8 Hz, 1H, Ph-CH2-CH-), 4.56 (d, J = 3.6 Hz, 1H, H-1), 4.03-3.94 (m, 1H, H-6a), 3.66-3.58 (m ,1H, H-2), 3.49-3.39 (m, 3H, H-6b, H-3, H-4), 3.28-3.24 (m, 4H, -OCH3, H-5), 3.00-2.89 (m, 3H, Ph-CHa-CH-, -NH-CH2-), 2.81 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 1.39-1.19 (m, 10H), 0.86 (t, J = 6.7 Hz, 3H); 13C NMR (100 MHz, d6-DMSO) δ 157.9, 136.3, 129.5, 128.0, 126.2, 101.7, 99.4, 81.5, 68.6, 67.5, 62.5, 54.6, 40.3, 39.2, 31.2, 29.9, 28.4, 26.3, 22.0, 13.9; LC-MS m/z calcd for C23H37N2O6 [M + H]+ 437.2, found 437.2.

Synthesis of cyclohexyl urea derivative 20 Compound 4 (75 mg, 0.254 mmol) and cyclohexyl isocyanate (0.032 mL, 0.254 mmol) were mixed and stirred for 6 hours. After THF was removed, the desired product 20 was obtained as a white solid (85 mg, 80%), mp 217.0-219.0 °C. 1H NMR (400 MHz, d6-DMSO at 50 °C) δ 7.33-7.17 (m, 5H), 6.00 (d, J = 7.1 Hz, 1H, -NH-Cy), 5.66 (d, J = 8.3 Hz, 1H, -NH-CH-), 5.01 (s, 1H, -OH), 4.80 (dd, J = 6.2, 4.1 Hz, 1H, Ph-CH2-CH-), 4.59 (d, J = 3.6 Hz, 1H, H-1), 4.03-3.95 (m, 1H, H-6a), 3.66-3.59 (m ,1H, H-2), 3.51-3.41 (m, 3H, H-6b, H-3, H-4), 3.29-3.26 (m, 5H, -CH in Cy, -OCH3, H-5), 2.93 (dd, J = 14.3, 4.1 Hz, Ph-CHa-CH-), 2.82 (dd, J = 14.3, 6.2 Hz, 1H, Ph-CHb-CH-), 1.801.02 (m, 10H); 13C NMR (100 MHz, d6-DMSO) δ 157.3, 136.3, 129.6, 128.0, 126.2, 101.7, 99.3, 81.5, 68.7, 67.5, 62.4, 54.61, 54.56, 47.6, 40.3, 33.2, 25.2, 24.3; LC-MS m/z calcd for C22H33N2O6 [M + H]+ 421.2, found 421.2.


Page 36 of 43

Page 37 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Synthesis of 6-heptynyl urea derivative 21 In a 50 mL RBF, 6-heptynoic acid (43 mg, 0.330 mmol) was dissolved in 3 mL anhydrous THF, (anhydrous) at rt, then TEA (0.070 mL, 0.508 mmol, 2 equiv) and DPPA (0.101 mL, 0.457 mmol, 1.8 equiv) were added to the reaction mixture. The reaction was stirred at 60 °C for 3 hours after which the isocyanate was obtained, the reaction mixture was cooled to rt, and compound 4 (75 mg, 0.254 mmol) was added, and the reaction mixture was then stirred at rt for 8 h. After the reaction was complete as indicated by TLC and 1H NMR, the reaction mixture was concentrated on a rotavap, the residue was taken up in 20 mL of DCM and 10 mL of water, and the aqueous phase was extracted with 15 mL of DCM twice. The combined organic phase was dried over sodium sulfate (anhydrous), and the crude product was obtained after the solvent was removed on a rotavap. The crude was purified using flash chromatography on silica gel with a gradient solvent system from pure DCM to 2% MeOH/DCM to afford compound 21 as a white solid (89 mg, 84%), Rf = 0.4 in 5% MeOH/DCM, mp 211.0-213.0 °C. 1H NMR (400 MHz, d6-DMSO) δ 7.31-7.17 (m, 5H), 6.07 (t, J = 5.7 Hz, 1H, -NH-CH2-), 5.72 (d, J = 8.5 Hz, 1H, -NH-CH-), 5.08 (s, 1H, -OH), 4.79 (dd, J = 6.4, 4.0 Hz, 1H, Ph-CH2-CH-), 4.57 (d, J = 3.6 Hz, 1H, H-1), 4.03-3.95 (m, 1H, H6a), 3.65-3.59 (m ,1H, H-2), 3.49-3.40 (m, 3H, H-6b, H-3, H-4), 3.28-3.23 (m, 4H, -OCH3, H-5), 3.02-2.96 (m, 2H, -NH-CH2-), 2.93 (dd, J = 14.2, 4.0 Hz, 1H, Ph-CHa-CH-), 2.81 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.74 (t, J = 2.6 Hz, 1H), 2.19-2.12 (m, 2H), 1.49-1.38 (m, 4H);

13

C

NMR (100 MHz, d6-DMSO) δ 157.9, 136.3, 129.5, 128.0, 126.2, 101.7, 99.4, 84.4, 81.5, 71.2, 68.6, 67.5, 62.5, 54.6, 40.3, 38.6, 29.1, 25.4, 17.4; LC-MS m/z calcd for C22H31N2O6 [M + H]+ 419.2, found 419.2.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 43

Synthesis of 10-undecynyl urea derivative 22 Following the same method for the synthesis of 21, compound 22 was prepared using undecynoic acid (61 mg, 0.330 mmol) as the starting material. The crude was purified using flash chromatography on silica gel with a gradient solvent system from pure DCM to 2% MeOH/DCM to afford compound 22 as a white solid (97 mg, 80%), Rf = 0.5 in 5% MeOH/DCM, mp 183.0185.0 °C. 1H NMR (400 MHz, d6-DMSO) δ 7.30-7.17 (m, 5H), 6.04 (t, J = 5.6 Hz, 1H, -NH-CH2), 5.71 (d, J = 8.6 Hz, 1H, -NH-CH-), 5.08 (d, J = 6.0 Hz, 1H, -OH), 4.79 (dd, J = 6.4, 3.9 Hz, 1H, Ph-CH2-CH-), 4.56 (d, J = 3.6 Hz, 1H, H-1), 4.02-3.94 (m, 1H, H-6a), 3.65-3.58 (m ,1H, H-2), 3.48-3.40 (m, 3H, H-6b, H-3, H-4), 3.28-3.23 (m, 4H, -OCH3, H-5), 3.00-2.89 (m, 3H, -NH-CH2, Ph-CHa-CH-), 2.81 (dd, J = 14.2, 6.4 Hz, 1H, Ph-CHb-CH-), 2.71 (t, J = 2.6 Hz, 1H), 2.14 (dt, J = 6.9, 2.6 Hz, 2H), 1.49-1.18 (m, 12H); 13C NMR (100 MHz, d6-DMSO) δ 157.9, 136.3, 129.6, 128.0, 126.2, 101.7, 99.4, 84.5, 81.5, 71.0, 68.6, 67.6, 62.5, 54.6, 40.3, 39.2, 29.9, 28.6, 28.4, 28.0, 27.9, 26.3, 17.6; LC-MS m/z calcd for C26H39N2O6 [M + H]+ 475.2, found 475.2.

Synthesis of phenyl urea derivative 23 Compound 4 (75 mg, 0.254 mmol) and phenyl isocyanate (0.028 mL, 0.254 mmol) were mixed and stirred at rt for 8 hours. THF was removed using the rotavap to afford compound 23 as a white solid (89 mg, 85%), mp 255.0-257.0 °C. 1H NMR (400 MHz, d6-DMSO at 50 °C), δ 8.57 (s, 1H), 7.40-7.35 (m, 2H), 7.30-7.26 (m, 4H), 7.25-7.19 (m, 3H), 6.92-6.88 (m, 1H), 6.06 (d, J = 8.7 Hz, 1H, -NH-CH-), 5.10 (d, J = 6.1 Hz, 1H, -OH), 4.83 (dd, J = 6.1, 4.1 Hz, 1H, Ph-CH2-CH-), 4.66 (d, J = 3.6 Hz, 1H, H-1), 4.06-3.97 (m, 1H, H-6a), 3.77-3.70 (m ,1H, H-2), 3.57-3.45 (m, 3H, H6b, H-3, H-4), 3.36-3.29 (m, 4H, -OCH3, H-5), 2.94 (dd, J = 14.3, 4.1 Hz, 1H, Ph-CHa-CH-), 2.84 (dd, J = 14.3, 6.1 Hz, 1H, Ph-CHb-CH-); 13C NMR (100 MHz, d6-DMSO) δ 154.9, 140.3, 136.3,


Page 39 of 43

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

129.6, 128.0, 126.2, 121.0, 117.4, 101.7, 99.2, 81.3, 68.4, 67.5, 62.6, 54.7, 54.3, 40.3; LC-MS m/z calcd for C22H27N2O6 [M + H]+ 415.2, found 415.2.

Synthesis of 4-bromophenyl urea derivative 24 Compound 4 (75 mg, 0.254 mmol) and 4-bromophenyl isocyanate (50 mg, 0.254 mmol) were mixed and stirred at rt for 24 hours. THF was removed using the rotavap to give the crude, which was purified by column chromatography using 2% MeOH/DCM to afford compound 24 as a white solid (102 mg, 82%), Rf = 0.6 in 2% MeOH/DCM, mp 268.0-270.0 °C. 1H NMR (400 MHz, d6DMSO) δ 8.76 (s, 1H), 7.42-7.17 (m, 9H), 6.12 (d, J = 8.8 Hz, 1H, -NH-CH-), 5.22 (d, J = 6.2 Hz, 1H, -OH), 4.82 (dd, J = 6.3, 3.9 Hz, 1H, Ph-CH2-CH-), 4.65 (d, J = 3.6 Hz, 1H, H-1), 4.05-3.96 (m, 1H, H-6a), 3.76-3.68 (m ,1H, H-2), 3.55-3.44 (m, 3H, H-6b, H-3, H-4), 3.31-3.27 (m, 4H, OCH3, H-5), 2.94 (dd, J = 14.3, 3.9 Hz, 1H, Ph-CHa-CH-), 2.82 (dd, J = 14.3, 6.3 Hz, 1H, PhCHb-CH-);

13

C NMR (100 MHz, d6-DMSO) δ 154.7, 139.7, 136.3, 131.4, 129.6, 128.0, 126.3,

119.3, 112.3, 101.7, 99.1, 81.3, 68.4, 67.5, 62.6, 54.7, 54.3, 40.3; LC-MS m/z calcd for C22H26BrN2O6 [M + H]+ 493.1, found 493.0.

Synthesis of 1-naphthyl urea derivative 25 Compound 4 (75 mg, 0.254 mmol) and 1-naphthyl isocyanate (0.037 mL, 0.254 mmol) were mixed and stirred at rt for 8 hours. Solvent was removed using the rotavap to give the product 25 as a white solid (100 mg, 85%), mp 257.0-259.0 °C. 1H NMR (400 MHz, d6-DMSO at 50 °C) δ 8.66 (s, 1H), 8.14 (d, J = 8.2 Hz, 1H), 8.07-8.04 (m, 1H), 7.58-7.48 (m, 3H), 7.44-7.38 (m, 1H), 7.317.25 (m, 4H), 7.24-7.19 (m, 1H), 6.67 (d, J = 8.7 Hz, 1H), 5.15 (d, J = 6.2 Hz, 1H, -OH), 4.84 (dd, J = 6.2, 4.1 Hz, 1H, Ph-CH2-CH-), 4.72 (d, J = 3.6 Hz, 1H, H-1), 4.06-4.01 (m, 1H, H-6a), 3.86-


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 43

3.77 (m ,1H, H-2), 3.64-3.46 (m, 3H, H-6b, H-3, H-4), 3.41-3.32 (m, 4H, -OCH3, H-5), 2.96 (dd, J = 14.3, 4.1 Hz, 1H, Ph-CHa-CH-), 2.85 (dd, J = 14.3, 6.2 Hz, 1H, Ph-CHb-CH-); 13C NMR (100 MHz, d6-DMSO) δ 155.3, 136.3, 135.0, 133.7, 129.6, 128.3, 128.0, 126.3, 125.9, 125.7, 125.3, 125.0, 121.8, 121.2, 115.7, 101.8, 99.3, 81.4, 68.6, 67.6, 62.6, 54.7, 54.5, 40.3; LC-MS m/z calcd for C26H29N2O6 [M + H]+ 465.2, found 465.2.

Supporting Information Available: The 1H NMR and 13C NMR spectra for compounds 4, 7-25, the 1H NMR spectra at variable temperature for compounds 11, 12, 16, 20, 21, 25 are provided; the 2D NMR spectra for compounds 4, 7, 11, 12, 21, 22 are also included. The optical images in full sizes, additional rheological experimental results are also included. The gel photos for different tests including spontaneous gelation, naproxen controlled release, chloramphenicol sustained release, and toluidine blue dye diffusions; FTIR spectra of the naproxen and chloramphenicol release from gels are also provided.

Acknowledgement: We are grateful to the financial support from National Science Foundation grant CHE#1313633.

References: (1) Kumar, D. K.; Steed, J. W. Supramolecular gel phase crystallization: orthogonal self-assembly under non-equilibrium conditions. Chem. Soc. Rev. 2014, 43, 2080-2088. (2) Maggini, L.; Bonifazi, D. Hierarchised luminescent organic architectures: design, synthesis, self-assembly, self-organisation and functions. Chem. Soc. Rev. 2012, 41, 211-241. (3) Peters, G. M.; Davis, J. T. Supramolecular gels made from nucleobase, nucleoside and nucleotide analogs. Chem. Soc. Rev. 2016, 45, 3188-3206. (4) Babu, S. S.; Praveen, V. K.; Ajayaghosh, A. Functional π-Gelators and Their Applications. Chem. Rev. 2014, 114, 1973-2129. (5) Estroff, L. A.; Hamilton, A. D. Water Gelation by Small Organic Molecules. Chem. Rev. 2004, 104, 1201-1217. 39 ACS Paragon Plus Environment

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Langmuir

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Lau, K. H. A. Peptoids for biomaterials science. Biomaterials Science 2014, 2, 627-

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