Alkyl 16.alpha.- and -.beta.-glycosides of a series of N3-alkyl homologues of streptozotocin were synthesized from glucosamine hydrochloride. These compounds, when tested against ascites Sarcoma 180, Ehrlich ascites carcinoma, or leukemia L1210, exhibited potent antitumor activities, and antibacterial and diabetogenic activities were eliminated. The acute toxicities of these compounds were lower than that of streptozotocin. The methyl, ethyl, n-propyl and n-butyl glycosides of streptozotocin, whether .alpha.- or .beta.-anomers, all showed higher antitumor activities than streptozotocin itself. The most active compound was the methyl .beta.-streptozotocin.