PRODUCTS FROM FURANS .7. A GENERAL-ROUTE FOR THE SYNTHESIS OF ALPHA-(1,2-CIS) AND BETA-(1,2-TRANS) GLYCOCONJUGATES VIA 1-O-ACYL AND 1-O-ETHOXYCARBONYL-2-AZIDO-2,3-DIDEOXYGLYCOPYRANOSIDES

A methodology for the synthesis of 2,3,6-trideoxy- and 2,3-dideoxy-2-aminoglycosides is presented. 2,3-Dideoxyhex-2-enopyranos-4-uloses (named also as 2H-pyran-3(6H)-Ones) were used for the synthesis of 1-O-acetyl, 1-O-ethyloxycarbonyl and 1-S-phenyl-2,3,6-trideoxy-(or 2,3-dideoxy)-2-azidoglycopyranosyl donors. Glycosidation of the above thio-ethers with a variety of alcohols in the presence of N-bromosuccinimide as activator yielded predominantly alpha-glycosides, while acetates afforded beta-glycosides when TMSOTf was used as a promoter. The coupling of carbonates using tin tetrachloride or TMSOTf proved to be the most successful procedure, yielding the beta-glycoside as the predominant product. Thus, glycoconjugates of aminosugars, steroids and aminoacids have been synthesized.