SOME FURTHER RING-OPENING REACTIONS OF METHYL 4,6-O-BENZYLIDENE-2,3-DIDEOXY-2,3-EPIMINO-ALPHA-D-ALLOPYRANOSIDE AND ITS DERIVATIVES

Modifications have been made to the preparation of methyl 4,6- O-benzylidene-2,3-dideoxy-2,3-epimino-α-D-allopyranoside from derivatives of 2-amino-2-deoxy-D-glucose, which permit it to be prepared in high yield and on a large scale. Further, ring-opening reactions of the epimine and its N-substituted derivatives have been studied with halide ion under neutral and acidic conditions. It has been found that anomalous, diequatorial ring-opening occurs when the free epimine is treated with ammonium halides (except the fluoride) in N,N-dimethylformamide, but, with its N-substituted derivatives, diaxial ring-opening predominates, although diequatorial ring-opening is significant in many cases. Under acidic conditions, the free epimine undergoes hydrolysis of the benzylidene group, without rupture of the epimine ring, but its N-substituted derivatives undergo predominant, diaxial ring-opening before hydrolysis of the benzylidene group. Ring-opening reactions of the N-methanesulphonyl and N-acetyl derivatives with azide occur trans-diaxially and trans-diequatorially, respectively. © 1968.