NH 链阳 CH3 CH-CH-CO- NH-CH-CO一N—cH CH3 性菌 素A CH3 Co— CH-NH-CO-C H CH3 CH3 链阳性菌素B NEe H NH 0 CH 0= 0 N(CHy (C2HS)2N Quinupristin Dalt pristin链阳 性菌素A 链阳性菌素 B