1-N-acylation of gentamicin C1a by a cyclic, chiral gamma-amino-alpha-hydroxy acid related to the (S)-4-amino-2-hydroxybutyric acid.

A semisynthetic aminoglycoside antibiotic 15, containing a cyclic gamma-amino-alpha-hydroxy acid, related to the 1-N-4-amino-2-hydroxybutyric acid (AHBA) side chain of butirosins and amikacin, has been prepared. Conveniently protected 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a (12) was condensed with the phtalimido active ester 10 to give after catalytic reduction and deprotection, the hitherto unknown 1-N-substituted gentamicin C1a 15. The requisite side chain was synthesized from the readily available D-(-)-quinic acid. The antibacterial properties of 15 are given.