An Asymmetric Synthesis of D- And L-Mannosamine

The addition of ammonia to the ethylenic bond of D-arabo-tetraacetoxy-1-nitrohexene-1 was stereospecific and formed a crystalline product, 1-nitro-1-deoxy-N-acetyl-D-mannosaminol. Application of the Nef reaction to this compound gave 2-amino-2-deoxy-D-mannose, which was isolated as the crystalline pentaacetate and further characterized as the hydrochloride by deacetylation with hydrochloric acid. In the deacetylation of the pentaacetate with barium methoxide, however, an abnormal epimerization occurred to yield N-acetyl-D-glucosamine.L-Mannosamine pentaacetate was synthesized in a similar manner from L-arabo-tetra-acetoxy-1-nitrohexene-1.