Stereoselective synthesis of novel five-membered homoazasugars. A convenient route to all-cis tetrasubstituted pyrrolidines

We present a highly stereoselective procedure for the preparation of (2S and 2R,3S,4R,5S)-5-methyl-3,4-dihydroxy-2- ethoxycarbonylmethylpyrrolidines based on conjugate addition of ammonia to unsaturated aldonic esters derived from d-ribose followed by tandem cyclization. Derivatisation of these compounds to 2-hydroxyethyl-, benzymidazolylmethyl-, biphenyl-1-aminoethyl and naphthalene-l-aminoethyl-pyrrolidines is also presented.