Aminodesoxyzucker und glycosylamin-synthesen durch oxyaminierung von hex-2-enopyranosiden und hex-1-enitolen. Synthese des N-acetylmycosamins

The vicinal cis-oxyamination of ethyl 4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside (1) and of methyl 4-O-acetyl-2,3,6-trideoxy-α-D-erythro-hex-2-enopyranoside (11) as well as of 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-(17) and -D-lyxo-hex-1-enitol (23) with Chloramine T-osmium tetraoxide was investigated (Sharpless reaction). The hex-2-enopyranosides 1 and 11 yielded the corresponding 3-deoxy-3-p-toluenesulfonamido-and 2-deoxy-2-p-toluenesulfonamido-hexopyranosides with the manno configuration in the ratio 2:1. The glycals 17 and 23 reacted with formation of the corresponding α-D-gluco and α-D-galactoN-tosyl-glycosylamines and of the 2-deoxy-2-p-toluenesulfonamidoglycoses in the ratio 3:1. The stereospecifity and the regioselectivity of the reactions are discussed. Quantum chemical calculations on models for the hex-2-enopyranosides 1 and 11 suggest a 3+2] cycloaddition of the N-tosylimido osmium(VIII) oxide in preference to a 2+2] mechanism with participation of the metal species. The preparative importance of the oxyamination reaction is demonstrated by a simple synthesis of N-acetyl-mycosamine.