Synthesis of new branched-chain amino sugars

1,3-Dipolar cycloaddition of methylideneaniline N-oxide to sugar enones is described. The addition occurred exclusively from the side opposite to the aglycone affording the corresponding alkyl α-d-lyxo-hexopyranosid-(2,3:5′,4′)-phenylisoxazolidin-4-uloses. Hydrogenation of these compounds readily yielded the corresponding alkyl 3-deoxy-3-N-phenylaminomethyl-α-d-talopyranoside, that were readily transformed to the acetates. The structure and conformation of the bicyclic compounds were determined by 1H NMR studies and semi-empirical molecular orbital calculations employing the AM1 method.