Allopyranoside epimino

Y. Ali, A. C. Richardson, C. F. Gibbs, and L. Hough, Some further ring-opening reactions of methyl 4,6-0-benzylidene-2,3-dideoxy-2,3-epimino-a-D-allopyranoside and its derivatives, Carbohydr. Res., 1 (1968) 255-271. 

Treatment of methyl 4,6-0-benzylidene-2,3-dideoxy-2,3-epimino-a-D-allopyranoside with nitrous acid gave methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside in high yield (81%). The manno isomer likewise gave the same alkene, in 78% yield. The first step in these reactions is the formation of the unstable, yellow IV-nitrosoepimines, the alio isomer being isolated, and crystallized at —20° it was characterized by u.v. and i.r. measurements and by elemental analysis, and could be stored at —20° for a few days.213... 

Cleavage reactions of epimino derivatives of methyl 4,6-0-benzylidene-2,3-epimino-2,3-dideoxy-a-D-allopyranosides with ammonium halides led either to diaxial or diequatorial isomers, or mixtures of both (Table VI). 

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