Improved synthesis of 6-amino-6-deoxy-d-galactono-1,6-lactam and d-mannono-1,6-lactam from corresponding unprotected d-hexono-1,4-lactones

Regioselective bromination of unprotected d-galactono-1,4-lactone and d-mannono-1,4-lactone with PPh3/CBr4 led to 6-bromo-6-deoxy derivatives. These intermediates were treated with LiN3 and hydrogenated to give 6-amino-6-deoxy-d-galactono-1,6-lactam () and 6-amino-6-deoxy-d-mannono-1,6-lactam () in 74 and 67% overall yield, respectively.