Cyano-sugars. Part 3. Synthesis of 2-C-cyano-2-deoxy-sugars from 2-C-cyano-galactals and attempts to prepare pentofuranosyl cyanides from aldonic acid lactones with tosylmethyl isocyanide

Abstract

1,5-Anhydro-2-C-cyano-2-deoxy-D-lyxo-hex-1-enitol (2) reacted with sodium methoxide in methanol to give, after acetylation, methyl 3,4,6-tri-O-acetyl-2-C-cyano-2-deoxy-β-D-galactopyranoside (6) as the main product. Similar treatment of 1,5-anhydro-2-C-cyano-2-deoxy-1,2-O-isopropylidene-D-lyxo-hex-1-enitol (3) gave methyl 4,6-di-O-acetyl-2-C-cyano-2-deoxy-3-O-methyl-α-D- and -β-D-galactopyranoside (11) and (7), respectively, as the main products. Compounds (6), (7), and (11) were converted into their 2-C-acetamidomethyl analogues (8), (9), and (12), respectively, in high yield by catalytic hydrogenation in ethanol–acetic anhydride.

The formylaminomethylenation of 2,3 : 5,6-di-O-isopropylidene-D-mannono-1,4-lactone with tosylmethyl isocyanide gave (E)- and (Z)-2,5-anhydro-1-deoxy-1-formylamino-3,4 : 6,7-di-O-isopropylidene-1-tosyl-D-manno-hept-1-enitol [(17) and (18)]. The reaction of the main isomer (17) with 2 equiv, of sodium ethoxide in ethanol, gave ethyl [(1R)-O-ethyl-1-formylamino-3,4 : 6,7-di-O-isoproyplidene-aldehydo-α-D-manno-heptafuranos]uloside and its (1S)-epimer [(21) and (22)], and not 2,3 : 5,6-di-O-isopropylidene-α,β-D-mannofuranosyl cyanide, as expected. 2,3 : 5,6-Di-O-isopropylidene-D-gulono-1,4-lactone behaved similarly.