An eight step synthesis of deoxymannojirimycin from L-gulonolactone in 25% overall yield is reported the key step is the formation of a δ-lactam by the reduction of a 5-azidolactone. The preparations of mannonolactam front L-gulonolactone and of L-deoxymannojirimycin and L- mannonolactam from D-gulonolactone are described.