4,6-Di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranose (4,6-di-o-acetyl-D-pseudoglucal), prepared from 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arubinohex-1-enitol (tri-0-acetyl-D-glucal), was condensed, by catalysis with boron trifluoride, with an equivalent of the original glycal, to give crystalline 4,6-di-Oacetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranosyl 4,6-di-O-acetyl-2,3-dideoxy-a-D-erythro-hex-2-enopyranoside in 40-50% yield. The dienic disaccharide was cisoxyaminated with chloramine-T in the presence of osmium tetraoxide, furnishing in 72% yield an -2:3.5: 1 mixture of the 2,2'-dideoxy-2,2'-di-(p-toluenesulfonamido), 2,3'-dideoxy-2,3'-di-(p-toluenesulfonamido), and 3,3'-dideoxy-3,3'di-(p-toluenesulfonamido) derivatives of a-D-mannopyranosyl a-D-mannopyranoside 4,6,4',6'-tetraacetate.
Separation of the mixture, achieved partly before and partly after 0-deacetylation, was followed by high-yielding, reductive Ndesulfonylations of the individual isomers with sodium in liquid ammonia, to give two new disaccharides, namely, 2-amino-2-deoxy-cz-D-mannopyranosyl 2-amino-2deoxy-a-D-mannopyranoside and its 2,3'-diamino-2,3'-dideoxy isomer, and the known 3,3'-diamino-3,3'-dideoxy isomer. The amino sugars were isolated as their dihydrochlorides, and characterized further by preparation of their di-N-acetyl derivatives.