Synthesis of iminoalditol and N-alkyl iminoalditol derivatives of ribopyranosides

Iminoalditol analogs of ribopyranosides were prepared by reduction of a vinylogous urethane intermediate formed from methyl 2-C-(5-O-methanesulfonyl-β-d-ribofuranosyl)acetate (1) by treatment with sodium azide in DMF at reflux. The N-alkylated analogs were synthesized either by N-alkylation of the corresponding parent iminoaldithol or, more efficiently, from the product of the reaction of 1 with various alkylamines. The latter process involves an S_N2 substitution at C-5 by the amine followed by an intramolecular hetero-Michael reaction under basic conditions. The 'aglycon' of the iminoalditol was also modified through amidation and esterification.