Orally Absorbed Derivatives of the Î²-Lactamase Inhibitor Avibactam

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Orally Absorbed Derivatives of the #-Lactamase Inhibitor Avibactam. Design of Novel Prodrugs of Sulfate Containing Drugs. Eric M. Gordon, Matthew A. J. Duncton, and Mark Gallop J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.8b01389 • Publication Date (Web): 08 Oct 2018 Downloaded from http://pubs.acs.org on October 8, 2018

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Journal of Medicinal Chemistry

Orally Absorbed Derivatives of the -Lactamase Inhibitor Avibactam. Design of Novel Prodrugs of Sulfate Containing Drugs. Eric M. Gordon,* Matthew A. J. Duncton, and Mark A. Gallop Arixa Pharmaceuticals, 525 University Avenue, Suite 1350, Palo Alto, CA 94301 Keywords:

prodrug, sulfate, Avibactam, -lactamase inhibitor

Abstract: Only one FDA-approved -lactamase inhibitor has ever been orally available – clavulanic acid, approved in 1984. Avibactam, approved by FDA in 2015 is the first of a new class of BLI’s called diazabicyclooctanes, or “DBOs”. This class has much broader coverage than clavulanic acid, but can only be administered by intravenous injection. Herein, we describe the synthesis and testing of the first approved BLI to be rendered orally bioavailable since clavulanic acid (1984).

Introduction The present and growing threat of microorganisms resistant to current antibiotics is an issue that commands worldwide attention.1,2 In 1976, the first -lactamase inhibitor (clavulanic acid) was discovered3,4 and later commercialized in combination with a beta lactam antibiotic (amoxicillin) as an oral/intravenous drug (Augmentin). -Lactamase inhibitors (BLI’s) while lacking significant antibiotic activity themselves, protect -lactam antibiotics from destructive deactivating enzymes produced by microorganisms (β-lactamases).5,6 Since the 1980’s, BLI/antibiotic combinations have become a standard part of therapy.7-10 In the over 40 years since the discovery of clavulanic acid, several other -lactam derived BLI’s have been discovered and approved by FDA,11 but none are orally available. A significant consequence of these BLI’s being intravenous only is that they may not be given outside the hospital, greatly increasing treatment costs.

(“DBO’s”) proved to be potent inhibitors of several classes of therapeutically important - lactamases and one has been FDA approved (avibactam 1)15 .Several other DBO’s are being progressed clinically (2,3,4),11,16 but they also are intravenous only. 17 Figure 1 Avibactam and Other DBO’s

In the mid 1990’s an important new class of non-lactam containing BLI’s was discovered.12-15 These interesting compounds; diazabicyclooctanones

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Because of the continuous evolution or change in the prevalence of lactamases, most oral -lactam antibiotics have lost potency since they were first commercialized (~1990’s). If an oral BLI with much better coverage of -lactamases than clavulanic acid of could be discovered and combined with an oral -lactam antibiotic the combination could restore the antibiotic to its original potency levels.

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displacement of avibactam under mild conditions, the benzyl ester was hydrogenated under neutral conditions. Figure 2 Synthesis of Avibactam Prodrugs

Results Considering the avibactam structure as it relates to oral absorption, attention is drawn to the unusual O-sulfated hydroxamic acid functionality as originally described in 1982 by Gordon.18 Historical medicinal chemistry suggests a charged sulfate moiety should be viewed as a primary obstacle to good oral bioavailability.19 The other DBO’s in development also contain similar sulfate groups. No strategies or methods to prepare prodrugs of sulfate containing drugs have been described in the chemical literature. Esters of sulfates are generally considered to be alkylating agents. However an important observation was described in 2006 by Widlanski20 who showed that neopentyl groups and to a lesser extent isobutyl groups could be used as protecting groups on sulfates. In particular, the neopentyl groups were shown to be extremely stable, requiring high temperatures and aggressive nucleophiles for removal. This represents a pathway by which a sulfate ester could be modified as a stable, unreactive entity, and might be the first step in sulfate prodrug design21 vide infra. In order to synthesize avibactam O-neopentyl esters, a variety of approaches were undertaken. The most effective of these is described in Figure 2. Hydrogenolysis of O-benzyl intermediate 5 provided N-hydroxy 6 in quantitative yield.21 Compound 6 had been reported to be unstable, and was used immediately. Sulfuryl chloride was reacted with 2,2,dimethyl propanol to give the chlorosulfonate 7, which was then reacted with 6 affording sulfate ester 9 as an isolable, stable compound. To use this methodology in prodrug design we needed to overcome the reported difficult removal of the neopentyl group, and to perform this under conditions amenable to removal in vivo. This was achieved by employing an intramolecular displacement of sulfate 1 (avibactam). Hydroxy pivalic acid was esterified as the benzyl ester, and allowed to react with sulfuryl chloride and combined with 6 to yield stable 10. To test whether the free acid would perform the intramolecular

To mimic what might occur in vivo ,hydrogenolysis of 10, afforded the intermediate carboxylic acid 11 which rapidly expelled avibactam These mild conditions suggested that esterase cleavage in vivo could trigger the expulsion of avibactam systemically. In addition to expulsion of avibactam, fragmentation of the pro-moiety was shown by 1H and 13C NMR to produce pivalolactone by comparison with an authentic sample (Supplementary Materials). The rate of the intermediate acid expulsion of avibactam and production of pivalolactone was shown to be greatly accelerated when slightly less than 1 equivalent of NaHCO3 was used. Figure 3 Mechanism of Avibactam Release

The presence of the essential gem-dimethyl group in the promoiety, besides providing steric hindrance to prevent nucleophilic attack at the methylene adjacent to sulfate oxygen, also importantly exerts a gem-substituent/trimethyl lock effect22,23 which brings the carboxylate nucleophile closer to the displacement site. When tested in vivo, the


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immediate products of ester/esterase cleavage are avibactam 1 and pivalolactone 12, which is quickly hydrolyzed by water and esterases to hydroxy pivalic acid 13. The breakdown of 10 triggered by ester cleavage is illustrated in Figure 3. Intramolecular formation of the strained -lactone (4-exo tet)24,25 during displacement is driven by the O-sulfated hydroxamic acid (avibactam) being an excellent leaving group.26 The conclusions of Widlanski which stated that neopentyl sulfates were stable except to severe conditions was further confirmed by showing that compound 8 did not react with cysteinyl or glutathionyl organic soluble derivatives (as 10 is not soluble in water). The individual potential alkylation products were synthesized, but were not observed when the nucleophiles were incubated with 10 for 24 hrs at both ambient temperature and 37 degrees (see supplemental section).

The general concept of displacing avibactam by revealing through esterase cleavage an appropriately placed nucleophile as shown in 11, was extended to several other prodrug chemotypes in which the nucleophile and chain length of the promoiety were varied. Chemotypes 18,19,20 were also shown to be bioavailable in rat, monkey, dog (Table 1). Their expected cleavage products are shown in Figure 4. Figure 4 Other Avibactam Prodrug Chemotypes

Table 1 Bioavailability (%F) of Prodrugs in Rat, Monkey, and Dog Rat

Monkey

Dog

14

36

60

100

15

29

60

66

16

37

72

95

17

33

51

86

18

23

33

62

19

36

52

44

20

24

46

34

O

O

H2N N O

N

O S O O O

H2N N

R

N

O 19

R 14 15 16 18 20

O

O S O O O

O

O COOEt COO(CH2)6CH3 COOCH2CH2OCH3 CH2CH2COO(CH2)5CH3 CH2CH2OCO-o-CH3Ph

O

O O O

17

Compound 10 and several related ester analogs (1420) were prepared by the above route, and were tested for their oral bioavailability of avibactam in rat, monkey, and dog PK assays (details in supplementary materials). To be considered useful as a drug, compounds generally need to achieve F=30% or better. The compounds listed in Table 1 meet this criterium. For comparison, the oral bioavailability of avibactam was ~1% rat, 15% dog, 3% monkey.

Discussion and Conclusions Approximately 65% of all prescriptions for antibiotics are β-lactams – penicillins, cephalosporins, carbapenams, and monobactams5. The most prevalent resistance mechanism to these drugs is a family of 2700+ β-lactamase enzymes produced by bacteria that destroy β-lactam antibiotics. For many years now there have been no new safe and effective FDA-approved oral antibiotics with broad coverage for serious Gramnegative infections. Patients who in past years could have been treated with oral antibiotics now have to remain in the hospital and be treated with intravenous antibiotics. When paired with an appropriate oral β-lactam antibiotic, the prodrugs of avibactam described herein restore the antibiotic’s effectiveness (to be described elsewhere). To this end, a novel method of preparing prodrugs (and potentially protecting sulfates)27 of sulfate containing drugs was developed and applied to avibactam. The novel entities produced were shown to have significant bioavailability in rat, monkey and dog. Variations of the overall strategy employing a neopentyl center proximate to sulfate, and an endogenous enzyme triggered nucleophile (nucleophile can be varied, as can chain length) to perform the intramolecular displacement have been


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applied to design other promoieties. We also applied this prodrug methodology to other DBO’s. These results will be reported in due course.

EXPERIMENTAL SECTION General All reagents were purchased from commercial suppliers and used without further purification. All solvents were reagent, or HPLC grade. Analytical TLC was performed on silica gel 60 F254 plates and visualized by UV if possible, or by staining with KMnO4 dip, or phosphomolybdic acid in EtOH dip. Flash chromatography was carried out using an automated system with pre-packed silica columns. Yields refer to isolated yields of pure compounds (>95% purity characterized by 1H ,13C HPLC, MS, and for key compounds HRMS (Supplemental). 1H NMR and 13C NMR spectra were recorded on a 300 MHz spectrometer at ambient temperature. Chemical shifts are reported in parts per million (ppm) relative to deuterated solvent, or a TMS internal standard. Multiplicities are reported as follows: s = singlet; d = doublet, t = triplet; m = multiplet; br = broad. Preparation of (2S,5R)-6-hydroxy-7-oxo-1,6diazabicyclo[3.2.1]octane-2-carboxamide (6)28 A stirred mixture of (2S,5R)-6-(benzyloxy)-7-oxo1,6-diazabicyclo[3.2.1]octane-2-carboxamide 5 (550 mg, 2.0 mmol), palladium on carbon (10% by weight; 340 mg, 0.3 mmol) and MeOH (18 mL) was hydrogenated under 1 atm (balloon) until analysis by thin-layer chromatography (TLC) indicated completion of the reaction (approximately, 30 min; reaction monitored by TLC using MeOH / CH2Cl2 - 5:95 as eluent). The mixture was filtered through a pad of celite and the pad was rinsed thoroughly with MeOH (ca. 20 mL). The filtrate was concentrated under vacuum (waterbath temperature not exceeding 25 °C) to give the product as a clear and colorless oil. The oil was dried under vacuum for 1 h, and the residue was used immediately in the next step without further purification. Yield assumed quantitative. LC-MS: m/z = 186.0 [M+H]+ General method for related chlorosulfonyloxy intermediates. Preparation of neopentyl sulfurochloridate (7)20 Sulfuryl chloride (0.11 mL, 1.4 mmol) in Et2O (20 mL) was added dropwise to a stirred solution of 2,2-dimethylpropan-1-ol (0.21 g, 2.3 mmol) and pyridine (0.11 mL, 1.4 mmol) in Et2O (5 mL) at -78 °C under an atmosphere of nitrogen. The mixture was stirred at -78 °C for 30 minutes, then filtered through a pad of Celite. The filtrate containing a solution of the desired product in Et2O was used

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directly in the next step without further purification, or concentration. Preparation of (2S,5R)-2-carbamoyl-7-oxo-1,6diazabicyclo[3.2.1]octan-6-yl neopentyl sulfate (9) (2S,5R)-6-hydroxy-7-oxo-1,6diazabicyclo[3.2.1]octane-2-carboxamide (0.20 g, 1.1 mmol) was suspended in THF (50 mL) and the resulting suspension was cooled to 0 °C under an atmosphere of nitrogen. 1,8Diazabicyclo[5.4.0]undec-7-ene (177 L, 1.2 mmol) was added slowly to the cooled solution, and the mixture stirred for 10 min. An solution of neopentyl sulfurochloridate (0.25 g, 1.3 mmol) in Et2O was added to the reaction mixture in one portion. The mixture was stirred at 0 °C, and then allowed to warm slowly to ambient temp. and stirred overnight. The solution was decanted from the solid which had precipitated from the reaction mixture, and the solid was rinsed with EtOAc (x2). The combined organic layers were concentrated under vacuum, and the resulting solid was dissolved in DCM and purified by column chromatography on silica gel (12 g column) using EtOAc / hexanes (1:9 to 7:3) as eluent to give a solid product. The solid was triturated with MTBE to give the product (142 mg). The filtrate was concentrated to give another aliquot of product (50 mg). The total yield = 53%. LC-MS: m/z = 335.95 [M+H]+; 1H-NMR (300 MHz, CDCl3): δ 6.48 (br. s, 1H), 5.57 (br. s, 1H), 4.48 (d, J = 8.7 Hz, 1H), 4.18 (d, J = 8.7 Hz, 2H), 4.05 (d, J = 6.9 Hz, 1H), 3.363.32 (m, 1H), 3.02 (d, J = 12.3 Hz, 1H), 2.46-2.41 (m, 1H), 2.19-2.14 (m, 1H), 1.99-1.82 (m, 2H), 1.01 (s, 9H); 13C-NMR (75 MHz, CDCl3): δ 171.2, 167.0, 85.2, 62.0, 60.2, 47.2, 32.0, 26.0, 20.8, 17.5. . General method for synthesis of compounds (10), (14-20).20 Preparation of ethyl 3-(((((2S,5R)2-carbamoyl-7-oxo-1,6-diazabicyclo[3.2.1]octan-6yl)oxy)sulfonyl)oxy)-2,2-dimethylpropanoate 14 (2S,5R)-6-Hydroxy-7-oxo-1,6diazabicyclo[3.2.1]octane-2-carboxamide 5 (370 mg, 2.0 mmol) was dissolved in THF (7.0 mL) and 1,3-dimethyltetrahydropyrimidin-2(1H)-one (3.0 mL) and the resulting solution was cooled to -78 °C under an atmosphere of argon. A solution of NaHMDS in THF (1M; 2.2 mL, 2.2 mmol) was added dropwise, and the mixture was stirred at -78 °C for 10 min. A solution of ethyl 3((chlorosulfonyl)oxy)-2,2-dimethylpropanoate 8 (538 mg, 2.2 mmol) in THF (1 mL) was then added quickly to the reaction mixture via syringe. The syringe was rinsed with THF (3 × 0.5 mL), each rinse being added to the reaction mixture. After 10 min at -78 °C, the reaction mixture was allowed to warm to room temperature and stirred at room temperature until judged complete by LC-MS and


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TLC analysis (ca. 2 h). EtOAc (20 mL) and saturated aqueous NaHCO3 (20 mL) were added and the organic and aqueous layers were partitioned. The organic layer was washed with saturated NaHCO3 (20 mL), H2O (3 × 20 mL), brine (20 mL), dried (Na2SO4) and concentrated under vacuum to leave a crude residue. The residue was purified by column chromatography on silica gel using EtOAc/hexanes (1:9 to 1:0) as eluent to give the product (318 mg, 39%) as a solid. LC-MS: m/z = 394.1 [M+H]+; 1H NMR (300 MHz, CDCl3): δ 6.50 (s, 1H), 5.78 (s, 1H), 4.71 (d, J = 8.7 Hz, 1H), 4.59 (d, J = 8.7 Hz, 1H), 4.22-4.12 (m, 3H), 4.05 (d, J = 6.9 Hz, 1H), 3.34-3.30 (m, 1H), 3.01 (d, J = 12.3 Hz, 1H), 2.46-2.40 (m, 1H), 2.18-2.12 (m, 1H), 2.00-1.79 (m, 2H), 1.28-1.24 (m, 9H); 13C NMR (75 MHz, CDCl3): δ 174.2, 171.2, 167.1, 80.5, 61.9, 61.4, 60.2, 47.2, 42.8, 22.2, 21.7, 20.8, 17.5, 14.2.

1.98-1.79 (m, 2H), 1.30 (s, 3H), 1.29 (s, 3H); 13CNMR (75 MHz, CDCl3): δ177.6, 171.0, 167.0, 152.2, 140.5, 133.2, 80.0, 61.8, 60.2, 54.4, 47.0, 43.0, 21.8, 21.7, 20.7, 17.5, 9.3.

Synthesis of hepty 3-(((((2S,5R)-2-carbamoyl-7oxo-1,6-diazabicyclo[3.2.1]octan-6yl)oxy)sulfonyl)oxy)-2,2-dimethylpropanoate (15) (65 mg, 4%) as a solid. LC-MS: m/z = 464.3 [M+H]+; 1H-NMR (300 MHz, CDCl3): δ 6.48 (s, 1H), 5.71 (s, 1H), 4.71 (d, J = 9.6 Hz, 1H), 4.60 (d, J = 9.3 Hz, 1H), 4.18-4.04 (m, 4H), 3.34-3.29 (m, 1H), 3.02 (d, J = 11.7 Hz, 1H), 2.47-2.40 (m, 1H), 2.19-2.11 (m, 1H), 2.01-1.79 (m, 2H), 1.66-1.59 (m, 2H), 1.37-1.26 (m, 14H), 0.90-0.86 (m, 3H); 13C-NMR (75 MHz, CDCl ): δ 174.3, 171.1, 167.0, 3 80.5, 65.6, 62.0, 60.2, 47.2, 43.0, 31.8, 29.0, 28.6, 25.9, 22.7, 22.2, 21.8, 20.9, 17.6, 14.2.

Preparation of (2S,5R)-2-carbamoyl-7-oxo-1,6diazabicyclo[3.2.1]octan-6-yl ((3-methyl-2oxotetrahydrofuran-3-yl)methyl) sulfate (19) (35 mg) as a solid. LC/MS: m/z = 378.0 [M+H]+; 1H-NMR (300 MHz, d -DMSO): δ 7.53 (s, 1H), 6 7.38 (s, 1H), 4.68-4.64 (m, 1H), 4.54 (d, J = 9.3Hz, 1H), 4.32-4.27 (m, 2H), 4.09 (s, 1H), 3.89 (d, J = 6.0Hz, 1H), 3.21-3.13(m, 2H), 2.38-2.28 (m, 1H), 2.13-2.00 (m, 2H), 1.91-1.66 (m, 3H), 1.21 (s, 3H); 13C-NMR (75MHz, d -DMSO): δ 178.3, 171.0, 6 168.7, 77.9, 65.6, 61.7, 61.2, 46.3, 43.2, 31.2, 20.8, 19.1, 18.9.

Preparation of 2-methoxyethyl 3-(((((2S,5R)-2carbamoyl-7-oxo-1,6-diazabicyclo[3.2.1]octan-6yl)oxy)sulfonyl)oxy)-2,2-dimethylpropanoate (16) (72 mg, 19%) as a solid. LCMS: m/z = 424.3 [M+H]+; 1H-NMR (300 MHz, CDCl3): δ 6.48 (br. s, 1H), 5.56 (br. s, 1H), 4.72 (d, J = 8.7 Hz, 1H), 4.62 (d, J = 8.7 Hz, 1H), 4.33-4.22 (m, 2H), 4.17 (br. s, 1H), 4.05 (d, J = 6.9 Hz, 1H), 3.60 (t, J = 4.6 Hz, 2H), 3.38 (s, 3H), 3.33 (d, J = 11.1 Hz, 1H), 3.02 (d, J = 12.0 Hz, 1H), 2.46-2.41 (m, 1H), 2.18-2.13 (m, 1H), 1.98-1.84 (m, 2H), 1.31 (s, 3H), 1.29 (s, 3H); 13C-NMR (75 MHz, CDCl3), δ 174.1, 170.8, 166.9, 80.2, 70.2, 64.1, 61.8, 60.0, 59.0, 47.1, 42.9, 22.1, 21.6, 20.7, 17.4. Preparation of (5-methyl-2-oxo-1,3-dioxol-4yl)methyl 3-(((((2S,5R)-2-carbamoyl-7-oxo-1,6diazabicyclo[3.2.1]octan-6-yl)oxy)sulfonyl)oxy)2,2-dimethylpropanoate (17) (189 mg, 34%) as a solid. LCMS: m/z = 478.1 [M+H]+; 1H-NMR (300 MHz, CDCl3): δ 6.68 (br. s, 1H), 5.74 (br. s, 1H), 4.95-4.79 (m, 3H), 4.50 (d, J = 9.3 Hz, 1H), 4.14 (br. s, 1H), 4.03 (d, J = 7.2 Hz, 1H), 3.32 (d, J = 12.3 Hz, 1H), 3.02 (d, J = 12.3 Hz, 1H), 2.45-2.39 (m, 1H), 2.17-2.09 (m, 4H),

Preparation of hexyl 5-(((((2S,5R)-2-carbamoyl7-oxo-1,6-diazabicyclo[3.2.1]octan-6yl)oxy)sulfonyl)oxy)-4,4-dimethylpentanoate (18) (421 mg, 44%) as a solid. LC-MS: m/z = 478.0 [M+H]+; 1H-NMR (300 MHz, CDCl3): δ 6.48 (s, 1H), 5.59 (s, 1H), 4.51 (d, J = 8.7 Hz, 1H), 4.224.18 (m, 2H), 4.08-4.04 (m, 3H), 3.36-3.32 (m, 1H), 3.02 (d, J = 12.6 Hz, 1H), 2.47-2.41 (m, 1H), 2.33-2.28 (m, 2H), 2.18-2.13 (m, 1H), 2.01-1.79 (m, 2H), 1.72-1.59 (m, 4H), 1.35-1.31 (m, 6H), 0.99 (s, 6H), 0.91-0.87 (m, 3H); 13C-NMR (75 MHz, CDCl3): δ 173.6, 170.9, 167.1, 83.5, 64.9, 62.0, 60.2, 47.3, 34.3, 33.3, 31.6, 29.3, 28.7, 25.7, 23.6, 23.3, 22.7, 20.9, 17.6, 14.1.

Preparation of 5-(((((2S,5R)-2-carbamoyl-7-oxo1,6-diazabicyclo[3.2.1]octan-6yl)oxy)sulfonyl)oxy)-4,4-dimethylpentyl 2methylbenzoate (20) (231 mg, 40%) as a solid. LCMS: m/z = 484.06 [M+1]+; 1H-NMR (300 MHz, CDCl3): δ 7.90 (d, J = 7.5 Hz, 1H),7.40 (t, J = 7.5 Hz, 1H), 7.26-7.24 (m, 2H), 6.44 (br. s, 1H), 5.53 (br. s, 1H), 4.60 (d, J = 8.7 Hz, 1H), 4.35 (t, J = 7.1 Hz, 2H), 4.28 (d, J = 9.0 Hz, 1H), 4.17 (br. s, 1H), 4.03 (d, J = 7.2 Hz, 1H), 3.33 (d, J = 12.3 Hz, 1H), 2.99 (d, J = 11.7 Hz, 1H), 2.60 (s, 3H), 2.47-2.40 (m, 1H), 2.18-2.14 (m, 1H), 1.95-1.82 (m, 4H), 1.10 (s, 6H); 13C-NMR (75 MHz, CDCl3): δ 171.0, 167.5, 167.1, 140.5, 132.2, 131.9, 130.7, 129.5, 125.9, 83.7, 62.0, 61.2, 60.2, 47.2, 36.9, 34.0, 24.1, 23.8, 21.9, 20.8, 17.5.

Author Information Corresponding Author Eric M. Gordon Arixa Pharmaceuticals 525 University Avenue, Suite 1350 Palo Alto, CA 94301

[email protected] (650)-465-5783


5


Matthew A. J. Duncton [email protected] Mark A. Gallop [email protected]

Acknowledgement Authors acknowledge the synthesis work of Brian Wang, Jun Yu, Pingyu Ding, Eddy Low, and Jiawei Sun, of Synterys, Inc., and Ritu Lal for overseeing the pharmacokinetic studies.

Abbreviations BLI, - lactamase inhibitor DBO, diazabicyclooctanones

Notes The authors declare no conflict of interests.

Ancillary Information Full experimental details for the synthesis of compounds 9, 10 and 14 to 20, together with full compound characterization. NMR study showing release of pivalolactone 12 from compound 10. Reaction of compound 10 with model mimics of biological nucleophiles. Statement regarding animal experimentation, together with full experimental details of pharmacokinetics with avibactam prodrugs 14 to 20. Molecular formula strings spreadsheet for compounds 8 to 11, 14 to 20. The Supporting

Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jmedchem.8b00296.

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Clinical Applications, Nature Rev. Drug Discov., 2008, 7, 255-270. [20] L. S. Simpson ,T. S. Widlanski, A Comprehensive Approach to the Synthesis of Sulfate Esters, J. Am. Chem. Soc., 2006, 128, 1605–1610. [21] For related observations in sulfonic acids see, J. C. Roberts, H. Gao, A. Gopalsamy, A. Kongsjahju, R. J. Patch, Neopentyl Ester Protecting Groups for Aryl Sulfonic Acids, Tetrahedron Lett., 1997, 38, 355-358. [22] M. E. Jung, G. Piizzi, gem-Disubstituent Effect: Theoretical Basis and Synthetic Applications, Chem. Rev., 2005, 105, 1735-1766. [23] M. N. Levinea, R. T. Raines, Trimethyl Lock: A Trigger for Molecular Release in Chemistry, Biology, and Pharmacology, Chem. Sci., 2012, 3, 2412-2420. [24] Several other mechanisms can be considered for this transformation, however the observation by nmr of pivalolactone production following hydrogenolysis of 10 supports the 4-exo-tet displacement shown in Figure 3. [25] a.) J. E. Baldwin, Rules for Ring Closure, J. Chem. Soc., Chem. Commun., 1976, 734-736. b.) J. E. Baldwin, R. C. Thomas, L. I. Kruse, L.Silberman, Rules for Ring Closure: Ring Formation by Conjugate Addition of Oxygen Nucleophiles, J. Org. Chem, 1977, 42, 38463852. [26] The application of similar strategies for Sulfonic Acids are shown in: a.) L. Rusha, S. C.Miller, Design and Application of Esterase-Labile Sulfonate Protecting Groups, Chem. Commun., 2011, 47, 2038–2040. b.) Y. Li, B. Jandeleit, M. A. Gallop, N. Zerangue, P. A. Virsik, W. N. Fischer, Preparation of Internally Masked Neopentyl Sulfonyl Ester Prodrugs of Acamprosate, U.S. Pat. Appl. 2009, 0099253; Chem. Abstr. 2009, 150,

422929. c.) B. Jandeleit, Y. Li, M. A. Gallop, N. Zerangue, P. A. Virsik, W. N. Fischer, Preparation of Masked Carboxylate Neopentyl Sulfonyl Ester Cyclization Release Prodrugs of Acamprosate, PCT WO 2009, 033061; Chem. Abstr. 2009, 150, 329286. d.) B. Jandeleit, Y Li, M. A. Gallop, N. Zerangue, P. A. Virsik, and W-N. Fischer, Preparation of Simple Pantoic Acid Ester Neopentyl Sulfonyl Ester Cyclization Release Prodrugs of Acamprosate, PCT WO 2009, 033069; Chem. Abstr. 2009, 150, 329288. [27] The same chemical methodology could be employed in the protection of sulfate groups in synthesis. Judicious choice of the ester group could be made orthogonal to other protecting groups, etc. [28] a.) T. Abe, M. Okue, Y. Sakamaki, Preparation of Optically-Active Diazabicyclooctane Derivative and Method for Manufacturing Same, PCT WO 2012, 086241; Chem. Abstr. 2012, 157, 165634. b.) M. Lampilas, J. Aszodi, D. A. Rowlands, C. Fromentin, Azabicyclic Compounds, Including 1,3Diazabicyclo[2.2.1]heptan-2-one and 1,6Diazabicyclo[3.2.1]octan-7-one Derivatives, Preparation Thereof, and Use as Medicines, in Particular as Antibacterial Agents, PCT WO 2002, 010172; Chem. Abstr. 2002, 136, 136397.


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O

H 2N

H 2N N O

N N

O O S O OH Avibactam

O

O N S O O O

Prodrug of Avibactam

Table of Contents Graphic


O O

R

Orally Absorbed Derivatives of the Î²-Lactamase Inhibitor Avibactam

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