Methyl 2,3-anhydro

With sodium hydroxide, methyl 2,3-anhydro-a-D-allopyranoside yields methyl 3,6-anhydro-a-D-glucopyranoside by intramolecular attack on the epoxide ring by the 6-hydroxyl group.72 Methyl 2,3-anhydro-a-D-gulopyranoside behaves similarly, and its intermediacy accounts for the conversion of methyl 3,4-anhydro-a-D-galactopyrano-side into methyl 3,6-anhydro-a-D-galactopyranoside on treatment with alkali.67... 

Honeyman147 reported the synthesis of methyl 2,3-anhydro-/3-L-lyxopyranoside, and claimed that, on alkaline hydrolysis, this gives a 2 1 ratio of L-xyloside L-arabinoside, but these results could not be substantiated by Buchanan and R. Fletcher,68 who recorded different constants for the epoxide and for the disulfonic ester claimed147 to be the starting material for its synthesis. The same epoxide has been synthesized by Reist and coworkers,160 and its properties are in agreement with Buchanan and Fletcher s results. Ethyl or methyl 3,4-anhydro-/3-L-ribopyranoside undergoes substitution at C-4 in all the reactions thus far studied. Neither half-chair conformation would seem to be clearly favored, but the specificity observed can be rationalized by considering the steric and polar interactions that may arise in the transition state substitution at C-3 in conformation 58 would involve marked interactions between the nucleophile and... 

The racemic form of methyl 3,4-anhydro-/3-mycaroside (82) has been synthesized 35 it is an epoxide of a branched-chain sugar having the oxirane ring fused to the pyranose ring. Hydrolysis of the oxirane ring with hydrochloric acid in aqueous p-dioxane occurs with substitution at C-4, the (more accessible) secondary position, as would be expected from its favored °H, conformation (82) anticipated, because it is an analog of the 3,4-anhydro-D-allopyranoside derivatives considered previously (see p. 148). 

J. W. Rrajewski, P. Gluzinski, and A. Banaszek, Crystal and molecular structure of methyl 3,4-anhydro-a-DL-allopyranoside ring conformations in the 3,4-anhydropyranose system, Carbohydr. Res., 203 (1990) 195-203. 

J. Jary and K. Capek, Amino sugars. 5. Preparation of methyl-3,4-anhydro-6-deoxy-a-D-galactopyranoside derivatives, Collect. Czech. Chem. Commun., 31 (1966) 315-320. 

R. D. Guthrie, I. D. Jenkins, R. Yamasaki, B. W. Skelton, and A. H. White, Epoxidation with triphenylphosphine and diethyl azodicarboxylate. Part 1. Synthesis of methyl 3,4-anhydro-D-tagatofuranosides, J. Chem. Soc., Perkin Trans. 1, (1981) 2328-2334. 

---