Lyxofuranoside

A simple synthesis of the branched chain sugar, 2-C-methyl-D,L-lyxofuranoside 17 has been achieved by using the tin(ll) enolate of a I 3-dihydroxy-2-propanone derivative and methyl pyruvate (23). 

A base-catalyzed, elimination reaction was a key step in a synthesis of D-ribose from L-glutamic acid.188 In that work, L-glutamic acid was converted, by a series of reactions, into 5-0-benzyl-2,3-dideoxy-D-glycero-pentofuranose (157) from compound 157, a mixture of glycosides was obtained which, on treatment with bromine and calcium carbonate, gave the monobromo derivative 158 as a mixture of diastereoisomers. Base-catalyzed dehydrobromination of 158 afforded the unsaturated derivative 159. Hydroxylation of 159 with potassium permanganate or with osmium tetraoxide gave a mixture of methyl 5-0-benzyl-/3-D-ribofuranoside and methyl 5-O-benzyl-a-D-lyxofuranoside. 

For furanoid derivatives, 2,3-epoxides are readily formed from trans-related groups. Other stereochemical features do not appear to be important, and this reflects the mobility of the orientations on such five-membered rings. Here, eclipsing polar interactions between cis sulfonate and methoxyl groups are not likely to alter much on passing to the transition state and, accordingly, both anomers of methyl 2-O-methylsulfonyl-D-xylofuranoside form the 2,3-anhydro-D-lyxofuranoside on treatment22 with sodium methoxide at 0°. 

DL-Dihydrostreptose and its ribo isomer were similarly obtained. Birch reduction of 2-methyl-3-furoic acid, followed by addition of methanol, bromination, and dehydrobromination, gave 402 as a mixture of the isomers. Hydroxylation of 402 with osmium tetraoxide-so-dium chlorate, and subsequent treatment with acetone-sulfuric acid afforded three isomeric acetals (403-405). The structures of these compounds were assigned on the basis of their H-n.m.r. spectra. In addition, the relationship between 403 and 404 was established by hydrolysis and reglycosidation. The methyl esters 403-405 were quantitatively reduced to the corresponding alcohols. The mixture of alcohols obtained from 403 and 404 was converted into crystalline 5-deoxy-3-C-(hydroxymethyl)-l,2-0-isopropylidene-a-DL-ribofuran-ose (406), which was compared directly with a sample prepared from D-xylose. Methyl 5-deox y-3-C-(hydroxy methyl)-2,3-O-isopropy lidene-/3-DL-lyxofuranoside (407), obtained by reduction of 405 with lithium aluminum hydride, was hydrolyzed with dilute hydrochloric acid, to give a,/3-DL-dihydrostreptose.2,ifi... 

Compound 177 was purified through the corresponding methyl /3-L-glucopyranoside by treatment with methanol, ether, and silver carbonate (overall yield 42%). The same reaction was applied186 to methyl 5-0-benzoyl-2,3-0-isopropylidene-a-D-lyxofuranoside (178), which gave the bromide 180 (crude yield 98%). Evidently, com-... 

The deamination of the pentoside methyl 4-amino-4-deoxy-2,3-0-isopropylidene-a-D-lyxofuranoside paralleled that of the mannopy-ranoside 39a in that substitution (with inversion) and ring contraction occurred to give a-D-Iyxopyranoside (60%) and /B-l.-ribofuranoside (40%) derivatives as products.1243 In contrast, there was no ring... 

Only with o-lyxose was there any evidence of pyranoside formation early in the reaction. A slight reverse reaction, furanoside to pentose, was also noted for this sugar. This behavior is in agreement with the low conformational stability of the D-lyxofuranosides. However, no initial formation of D-arabinopyranosides was noted. 

A kinetic study of the methyl glycosidation of D-mannose was also made by Mowery.48 The more stable anomer, the a-D-mannofuranoside, was formed at a higher initial rate (see Table III) the proportions of both furanosides in the final equilibrium mixture was too small to permit accurate comparison of isomer distribution. The conformational stability of the D-mannofuranosides may be compared with that of the D-lyxo-furanosides the furanoid structures are similar, except for the bulky two-carbon group at 04 of the hexoside. This similarity is shown in the very small proportion of n-lyxofuranosides (see Table V) and of D-manno-furanosideo (see Table III) in the final equilibrium mixtures, and also in the initial formation of D-mannopyranosides48 and of D-lyxofuranosides.u... 

V. S. Murthy, A. S. Gaitonde, and S. P. Rao, One-pot conversion of 1,2-diols to epoxides —convenient preparation of methyl 2,3-anhydro-5-0-trityl-/ -D-lyxofuranoside and methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside, Synth. Common., 23 (1993) 285-289. 

Trimethyl-D-lyxofuranose was obtained by the hydrolysis of the products obtained by the methylation of methyl D-lyxofuranosides (ttf3 mixture).63 The product (XLVII) on oxidation with bromine, gave 2,3,5-trimethyl-D-lyxonolactone which was hydrolyzed extremely slowly in aqueous solution, and on oxidation with nitric acid followed by esterification methyl meso-dimethoxysuccinate was obtained. 

In connection with carbohydrates, (1,5,3,5,5W)-1,3-dimcthyl-2,9-dioxabicyclo 3.3.11 nonane has been prepared from dithiane and D-glucose263. An epoxide derived from D-xylose 195 has been opened regioselectively by means of compound 161 at the 4-position in 90% yield264. In the case of the methyl 2,3-anhydro-a-D-lyxofuranoside 196 the ring... 

Deoxy-a-L-lyxofuranosid Methyl-2, 3-O-carbony l-3-(1,3-di thian-2-yl)- E4, 84 (COCl2 + Diol)... 

Walker et al. have described by tliis method a seven-step synthesis of 4-thio-2-deox-y-i3-eri f/7ro-pentosc (37) from 2-dcoxy-D-erir/ira-pentosc via dithioacetals 35 and 36, involving inversion at C-4 by Mitsunobu reaction and final cyclization of the dithioacetal, accompanied by further inversion at C-4. Secrist et al.- have synthesized 39 from the ribose derivative 38 using the same method. Similarly, Imbach et al. have prepared 1,4-dithio-D-ribofuranosides 39 from L-lyxose and from D-ribose,and 1,4-dithio-L-lyxofuranosides 40 from D-ribose. Mackenzie... 

Methyl a-D-lyxofuranoside (13) forms a weak complex with cations Rp... 

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