LIGHT-SENSITIVE GLYCOSIDES.I1
J . Org. Chem., Vol. 37, No. 14, 197.2 2285
tent. Samples after 4 hr irradiation were also lyophilized and checked by paper chromatography as described above.
Registry No.-1, 34546-52-6; 2, 34546-53-7; 3, 34546-54-8; 4, 34546-55-9; 6-nitroveratryl alcohol, 1016-58-6.
Acknowledgments.-We wish to thank Dr. Asher Mandelbaum for his help in the interpretation of mass spectra. This work was supported by Grant No. AM05098 from the National Institutes of Health, Public Health Service.
Light- Sensitive Glycosides. 11. 2-Nitrobenzyl6-Deoxy-cr- L-mannopyranoside and 2-Nitrobenzyl 6-Deoxy-p-~-galactopyranoside URI ZEHAVI*AND ABRAHAM PATCHORNIK Department of Biophysics, T h e Weizmann Institute of Science, Rehovot, Israel Received October $6, 197'1 The two title compounds possessing 01 and p anomeric structures were prepared, characterized, and photochemically split to 6-deoxymannose (rhamnose) and 6-deoxygalactose (fucose), respectively. 2-Nitrobenzyl 6deoxy-2,3-isopropylidene-01-~-mannopyranoside was synthesized and the isopropylidene grouping subsequently removed by acid hydrolysis,without affectingthe nitrobenzyl glycoside.
I n the preceding paper1 we have described a 6-nitroveratryl and a 2-nitrobenzyl P-n-glucopyranoside. Both compounds mere found to be more stable to acid hydrolysis than benzyl 0-D-glucopyranoside and were susceptible to photolysis under conditions that do not affect the benzyl glucoside. I n the present work we tried to broaden the scope of our investigation to glycosides of different configurations and different anomeric structure. We also prepared and hydrolyzed an isopropylidene derivative without affecting the glycoside. Such an isopropylidene derivative might serve as a convenient intermediate in carbohydrate synthesis. Results and Discussion 2-Nitrobenzyl 6-deoxy-a-~-mannopyranoside(1) and 2-nitrobenzyl 6-deoxy-P-~-galactopyranoside (2) were prepared by the ZBmplen modification* of the KonigsKnorr reaction, followed by de-O-acetylation with barium methoxide and fractionation on silica gel. Compound 2 was accompanied by what is, most probably, the CY anomer. The ZBmplen modification was chosen as it was reported to yield clean 6-deoxy-amannopyran~sides.~ The optical rotations, uv, ir, and nmr spectra of the two compounds and their acetates (3 and 4) were in accord with the proposed structures (Scheme I). Only in the case of compound 4 (and hence compound 2), however, had the anomeric configuration firm support from the nmr ~ 7.5 Hz, that should correspond to axialdata, J I , = axial interaction present in the ,8 anomer. The anomeric configuration in compound 1 was established by its periodate oxidation to the dialdehyde 5 possessing a different rotation from the corresponding dialdehyde 6 obtained in a similar oxidation of compound 2. As a result, compound 1 was assigned as the a anomer. Irradiation of compounds 1 and 2 afforded quantitatively 6-deoxymannose (rhamnose) and 6-deoxygalactose (fucose), respectively, as determined by viewing the chromatograms. The reducing sugar tests gave too high yields (over 120y0)due to the interference of the (1) Part I: U. Zehavi, B. Amit, and A. Patohornik, J. Org. Chem., 87, 2281 (1972). (2) G. Zemplen, Ber., 68, 990 (1929). (3) P.A. J. Gorin and A. S. Perlin, Can. J. Chem., 87,1930 (1959).
SCHEME I
f-G> RO
0-CH,
OR
l,R= H 3, R = COCH,
OiN
2,R = H 4, R = COCH:,
7
5
0
6
H3C
CH3
7
formed aldehyde. In the preceding work this difficulty was overcome by the enzymic determination of Dglucose that was formed during the cleavage. The isopropylidene derivative (7) of compound 1 was prepared in high yield, using copper sulfate in acetone. The material absorbed at 3620 and 3480 cm-' (OH) indicative of a free hydroxy grouping. Such a group on (3-4, should be available for selective chemical modification. I n view of the increased stability of the 2-nitrobenzyl glycosides to acid hydrolysis, the isopropylidene moiety could be neatly removed by sulfuric acid in aqueous acetone (Figure 1) without affecting the glycoside function. The mass spectra of compounds 3 and 4 (Figures 2 and 3) are in principle similar to the spectra of the glucosides described bef0re.l The molecular ions, however, are absent and one observed four major primary fragments: M - acetic acid, m/e 365; 14 nitrobenzyl radical, m/e 289; M - nitrobenzyloxy
2286 J . Org. Chem., Vol. $7, No. 14, 1972 1001
I
ZEHAVIAND PATCHORNIK 1
1
I
.9
e I
I
I
IO
20
30
J
40
T I ME (hr)
Figure 1.-Acid hydrolysis of compound 7 ( 0 )and formation of compound 1 (A). For details see Experimental Section.
ferent for the two cases as a result of the difference in configuration and anomeric structure of compounds 3 and 4. A pronounced difference between compounds 3 and 4 can be found in the fragmentation patterns of compound 3, starting probably from m/e 289 to give an intense line line at m/e 244 (loss of HC02j. Subsequently a loss of acetic acid results in an ion of m/e 184. A less important fragmentation of the same compound is through the formation of m/e 229 (a possibility of m/e 289 losing acetic acid) and m/e 184 (loss of HC02j. A metastable peak is present only for the transition of m/e 244 to m/e 184. Only the second pattern is present in the spectrum of compound 4. It is of interest to
i L I
2 1
r--
c
184
40
----x
10
; ;
I i
I il I I r -4-
20 1111
113
1
I111
I
I
~IIIIIIL
I80
VO
11
289
I
3?5
260
220
m/e Figure 2.-Mass
spectrum of 2-nitrobenzyl 6-deoxy-2,3,4-tri-O-acetyl-a-~-mannopyranoside (3)
I36
1000 -0
5
80-
n
a
al
60 -
-------I
5 .c -0 40P)
I I :
229
xIo
2
I I
I
20 -
184
/
I II
I I I I I lul
I
1 1 I
II I
1
1 I
I
I
I
I . rn /e
Figure 3.-Mass
spectrum of 2-nitrobenxyl 6-deoxy-2,3,4-tri-0-acetyl-~-~-galactopyranoside (4).
radical, m/e 273; and nitrobenzyl (or an isomeric form) ion, m/e 136. The first three ions are further decomposed through the loss of acetic acid and ketene (60 and 42 mass units, respectively). The relative abundances of the parent fragments as well as the abundance of products of further degradation, occurring through the loss of 60 and 42 mass units, are dif-
note that both patterns are present in the spectrum of 2-nitrobenzyl 2,3,4,6-tetra-0-acetyl-/?-~-ghcopyranoside,l m/e 347 +m/e 302
+m / e 242 -+-m / e 200 1
\
m/e 287
7
LIGHT-SENSITIVE
GLYCOSIDES. 11
J . Org. Chem., Vol. $7, No. 14, 1972 2287
A
m /e
60 Figure 4.--Mass
100
140
I80
.
220 m/e
spectra of (A) 2-nitrobenzyl 6-deoxy-2,3-isopropylidene-oc-~-mannopyranoside (7); (B) 2-nitrobenzyl 6-deoxy2,3- (isopropylidene-ds)-a-~-mannopyranoside.
SCHEME I1 and metastable peaks are present for transitions other than the loss of 45 mass units. The two patterns are absent from the spectrum of 6-nitroveratryl 2,3,4,6tetra-0-acetyl-0-D-ghcopyranoside and present to a small extent in that of benzyl 2,3,4,6-tetra-O-acetyl-P-~glucopyranoside, W e 100 mle 85 In the mass spectra of compound 7 and its isopropylidene-cia derivative (mass units indicated in brackets) (Figure 4) one can easily interpret the following peaks: Experimental Section the molecular peak 1 4 , 339 (345); A I 1, 340 (346); Experimental procedures were the same as those reported in M CH, from isopropylidene, 324 (327); &/I - nitrothe preceding paper.’ Nmr spectra were also recorded on a benzyl, 203 (209); S4 - nitrobenzyloxy, 187 (193); Varian HA-100 instrument and colorimetric determinations were done on a Zeiss Model PMQ 11 spectrometer. nitrobenzyl, 136 (136); nitrosobenzyl, 120 (120), 100 Paper chromatograms were revealed by silver nitrate.4 Thick (106),and 85 (88), with a metastable peak a t m/e 72.3 laycr chromatography was done on “Chroma-1000” sheets, suggesting the following structures for the last two supplied by Mallinckrodt, 20 X 20 cm sheets were developed with ether-hexane (1:1) and viewed under a uv lamp, and the peaks (Scheme 11). band of the desired material was extracted with chloroform, In the present work we have demonstrated that lightfiltered, and evaporated. 6-Deoxy-~-mannose(L-rhamnose) and sensitive a- and @-glycosidesof saccharides other than 6-deoxy-~-galactose (L-fucose) were purchased from Pfanstiehl glucose can be conveniently prepared and derivatized. Laboratories, Waukegan, Ill. 2-Nitrobenxyl alcohol was a product of Fluka, Switzerland. The glycosides were photolyzed in high yield to the parent sugars. (4) N. Sharon and E. W. Jeanloz, J . Biol. Chem., 296, 1 (1960).
-
+
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J. 01.0. Chem., Vol. 37, No. 14, 1979
ZEHAVIAND PATCHORNIK
I t was then evaporated in vacuo by codistillation with benzene 2-Nitrobenzyl6-Deoxy-a-~-mannopyranoside (1). A.-A mixture of bromo-6-deoxy-2,3,4-tri-0-acetyl-a-~-mannopyranoside and the product was purified by thick layer chromatography on ( “acetobromorhamnose”)6 (2.1 g, 6.0 mmol), mercuric acetate two sheets: yield 102 mg (79%) of yellow oil; RSR0.52 (etherhexane, 1: l ) , [ a I z 3 D -22.7 & 0.1 (c 4.0, chloroform); nmr (100 (O,!) g), 2-nitrobenzyl alcohol (0.91 g, 6.0 mmol), and anhydrous MHz, CDCb) T 1.8-2.6 (m, 4, aromatic), 4.5-5.2 (unresolved calcium sulfate (1 g ) in absolute benzene (30 ml) under a calcium m, 6, CH2, H-1, H-2, H-3, H-4), 6.04 (octet, 1, H-5, Ja,a= chloride seal was stirred for 20 min inside a 50” bath and for 3 9.5, J6,e = 6.0 HE),7.81 (s, 3, OCOCH,), 7.92 (s, 3, OCOCH,), days a t room temperature. The mixture was filtered through a Celite filter with the aid of some benzene. The benzene solu7.94 (s, 3, OCOCH,), 8.72 (d, C-5 CH,). Irradiation a t T 8.72 tion was washed with water, dried over calcium chloride, and caused the collapse of the octet a t 7 6.04 to a doublet ( J = 9.5 evaporated in vacuo and the residue was left overnight in a methHa). Irradiation at 7 6.04 caused the collapse of the doublet at 7 8.72 to a singlet; the multiplet T 4.5-5.2 was also affected. anolic solution of barium methoxide (0.1 M , 25 ml). The soluAnal. Calcd for ClgH23010N: C, 53.64; H, 5.54. Found: tion was then neutralized with carbon dioxide, evaporated zn vacuo, and extracted with methanol, and the resulting solution C, 53.54; H , 5.64. 2-Nitrobenzyl 6-deoxy-2,3,4-tri-0-acetyl-p-~-galactopyranoside was evaporated on silica gel (10 g). The absorbed material was ( 4 ) was prepared as described for compound 3 but starting from placed on top of a silica gel column (100 g, 2 ern diameter) packed compound 2: yield 103 mg (79%) of yellow oil; RSR 0.41 in ethyl acetate. The column was washed with ethyl acetate (400 ml) and 107, acetone in ethyl acetate and the product was (ether-hexane, 1 : l ) ; [ O ~ ] ~ , D-19.4 =t0.2’ (c 1.0, chloroform); nmr (90 MHz, CDC1,) T 1.80-2.67 (m, 4, aromatic), 4.58-5.13 then eluted with an additional amount of the same solvent (500 (m, 5 , CR2,H-2, H-3, H-4), 5.39 (d, 1, H-1, J 1 , z= 7.5Hz), 6.14 ml). The product was homogeneous by tlc, RSR 0.83 (acetonemethanol, 3: l ) , RSR 0.32 (acetone-ethyl acetate, 1: 1). I t was (apparent q, 1, H-5, J4,a = 1.5, JS,6 = 6.5 Hz), 7.81 ( s , 3, OCOcrystallized from water to give 508 mg (287,) of elongated yellowCH3), 7.96 (s, 3, OCOCH,), 8.01 (s, 3, OCOCHp), 8.74 (d, 3, brownplates: mp 103’; [ a I z 4 D -18.3 & 0.3’(~0.9,ethanol); uv C-5 CH,). Irradiation at 334 Hz (H-5) causes the collapse of the 7 8.74 doublet to a singlet. max (ethanol) 257 nm ( e 5.6 X lo3); nmr (60 bIHz, dimethyl Anal. Calcd for C19H23010r\l:N, 3.29. Found: N, 3.25. sulfoxide-d6) T 1.8-2.4 (m, 4, aromatic), 5.13 (apparent d, benzylic CHz,J = 2.0 Hz), 8.87 (d, 3, C-5 CHI, J s , =~ 5 . 5 Hz). Photolysis of Compounds 1 and 2.-Samples (2.3 X 10-2 mM Anal. Calcd for C13H1707N.1/zH20:C, 50.69; H, 5.88; N, in 10% ethanol) were irradiated for 5 hr in closed Pyrex test 4.54. Found: C, 50.60; R, 5.88; N, 4.50. tubes and then analyzed for their saccharide content by the ParkJohnson color test for reducing sugars? using B-deoxy-~-mannose The crvstals lost water upon drying . - at 95’ for 3 hr and under high vacuum, mp 110-112’: and 6-deoxy-~-galactosestandards. Anal. Calcd for C13Hli07N: C, 52.17; H, 5.73. Found: C, For the purpose of paper (systems I and 11) and thin layer 52.20; H, 5 , 7 5 . chromatography (ethyl acetate-acetone) 1.0 m M solutions in B.-Compound 7 (0.27,) in a mixture of acetone and aqueous SOYo ethanol were irradiated for the same length of time. lY6 sulfuric acid (2: 1) was kept at room temperature (23”) and The photochemical reactions were carried out in a RPR-100 samples (10 pl) were applied for tlc (ethyl acetate-acetone, 1:1) apparatus (Rayonet, the Southern Co., Middletown, Conn.) after different time intervals. The plates were viewed under uv with 320-nm lamps. Periodate Oxidation of Compounds 1 and 2.s-Sodium metaand the spots corresponding to compounds 1 and 7 were extracted with ethanol (2.0 ml), filtered through a cotton plug, and read at periodate (0.6 ml, 100 mg/ml in water) was added to samples 257 nm. N o 2-nitrobenzyl alcohol, RSR 0.70 (ether-hexane, of compound 1 (2.67 mg in 0.3 ml of ethanol) and of compound 2 l : l ) , could be observed following 50 hr of hydrolysis. Com(2.06 mg in 0.3 ml of ethanol) and the solutions were stored pound 7 had RSR0.30 and compound 1 R S R0.0 in the last solin the dark at room temperature. The optical rotation of the solutions was followed and did not change between 4 and 16 hr. vent system. 2-Nitrobenzyl 6-Deoxy-p-~-galactopyranoside(2).-This comThe conversion to the dialdehydes 5 and 6, respectively (mol wt pound was prepared as described for compound 1 but with 255), was then assumed to be quantitative. Dialdehyde 5 amounts increased tenfold and starting from bromo-6-deoxyhad [ a ] % -96’ and dialdehyde 6 had +57”. 2-Nitrobenzyl 6-Deoxy-2,3-isopropylidene-a-~-mannopyrano2,3,4-tri-O-acetyl-~-galactopyranoside(“acetobromofucose”) .6 Following de-0-acetylation the mixture was absorbed on silica side (7).-Compound 1 (300 mg) and anhydrous copper sulfate gel (50 g) and placed on top of a silica gel column (350 g). The (3 g) were stirred vigorously in acetone (50 ml) overnight at column was first washed with ethyl acetate (1200 ml) and 5% room temperature. According to tlc already after 8 hr most of acetone in ethyl acetate (350 ml). An impure oily product the starting material was transformed into the isopropylidene derivative 7, RSR 1.0 (ethyl acetate-acetone, 1 : l ) . The mix(0.37 g) that appears to be the 01 anomer, RSR0.60 (ethyl aceture was filtered through a Celite pad with the aid of some additate-acetone, l : l ) , emerged on further elution with the same tional acetone and the solution was evaporated in vacuo, yieldsolvent (500 ml). The last material was eluted together with ining 353 mg of practically pure oil that was further purified by creasing amounts of compound 2, RSR 0.26 (ethyl acetate-acethick layer chromatography on two sheets. The product, 260 mg tone, 1:1) (1.0 g), in the next fractions of 10% acetone in ethyl (79%), was a yellow oil: [ a I z 6-17.5 ~ & 0.2” ( c 1.56, chloroacetate (500 ml) while chromatographically pure compound 2 was form); uv max (chloroform) 257 nm (e 6.5 X lo3); nmr (60 MHz, eluted subsequently by 2570 acetone in ethyl acetate (500 ml) CDCl,) 7 1.8-2.6 (m, 4, aromatic), 4.92 (apparent d, benzylic (1.3 g, 77,). I t was crystallized from a mixture of methanol CHz,J = 3.5 Hz), 8.46 and 8.63 (two s, 6, isopropylidene), 8.70 and water (but has high solubility in this mixture). The yellow (d, 3, C-5 CH3, J5,6 = 6.5 Hz). ~ =k 0.5’ crystals sinter at 46-48’ and melt at 136’: [ a I z 4+4.4 Anal. Calcd for C16H,,07N: N, 4.13. Found: N, 4.00. (c 0.69, ethanol); uv max (ethanol) 257 nm ( t 5.8 X lo3); nmr 2-Nitrobenzyl 6-deoxy-2,3-(isopropylidene-d~)-a-~-mannopy(60 RIHz, dimethyl sulfoxide-ds) T 1.8-2.6 (m, 4, aromatic), 4.47 ranoside was prepared in an analogous manner starting from (apparent d, 2, benzylic CHZ, J = 2.0 Hz), 8.86 (d, 3, C-5 CH3, compound 1 (10 mg) and using acetone-&. J5,6 = 6.0 HZ). Anal. Calcd for C13H170iK.11/2HzO: C, 47.88; H, 6.18; N , 4.29. Found: C, 48.13; H , 6.10; N, 4.32. Registry No.-1, 34546-48-0; 2, 34546-49-1 ; 3, The water of crystallization could be removed by drying the 34546-50-4; 4,34578-22-8; 7,34546-51-5. crystals at 75” for 4 hr and under high vacuum, mp 136”. Anal. Calcd for C13H1,07N: C, 52.17; H, 5.73. Found: Acknowledgments. -Our thanks are extended to Dr. C, 52.39; H , 5.60. 2-Nitrobenzyl6-Deoxy-2,3,4-tri-0-acetyl-01-~-mannopyranosideAsher Mandelbaum for his help in the interpretation of mass spectra. This work was supported by grant AM (3).-Compound 1 (100 mg) was dissolved in pyridine (1.0 ml), and acetic anhydride (0.5 ml) was added. The reaction 05098 from the n’ational Institutes of Health, Public mixture was left overnight at room temperature, a crystal of ice Health Service. was then added, and the mixture was left for an additional 2 hr. ( 5 ) E. Fischer, iM. Bergmann, and H. Rabe, Ber., 68, 2362 (1920). (6) H. .M.Flowers, A. Levy, and N . Sharon, Carbohgd. Res., 4, 189 (1967).
(7) J. T. Park and M. J. Johnson, J. Bzol. Chem., 181, 149 (1949). (8) A. J. Carlson and A. S. Perlin, Can. J . Chem.. 84, 1804 (1956).
