Nitrogen-containing carbohydrate derivatives. XIV. Configurational studies on amino-sugars using cuprammonium solutions.
A study has been made of the optical rotational shifts and conductance changes in cuprammonium solutions of eight isomeric amino-glycosides. The results are in agreement with the findings of Reeves for vicinal diol systems. Care must be taken in using small optical rotational shifts alone as evidence for the absence of complexing with a vic-amino-alcohol grouping. These techniques have been used to relate methyl 5-amino-1,3-O-benzylidene-5-deoxy-β-D-fructoside and -α-L-sorboside to their respective hydroxy-compounds.
Nitrogen-containing carbohydrate derivatives
An epimeric pair 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-talo-heptitol and 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-galacto-heptitol, was synthesized from D-mannose. The absolute configuration at C-2 was based on the rules relating the signs of the Cotton effect of the o.r.d. curves and the c.d. maxima to the configuration at C-2 of the carbohydrate C-nitro alcohols. This assignment was confirmed by chemical degradation of 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-D-talo-heptitol to D-serine. Another epimeric pair, 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-L-manno-heptitol and 2-acetamido-1,2-dideoxy-1-nitro-D-glycero-L-gluco-heptitol, was synthesized, and the configurations at C-2, determined by optical methods, agreed with those established by chemical methods.
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.