(一)概述头孢菌素类抗生素(cephalosporiins雪其母核为头孢烷酸,同时在7位都有氨基,在2位都有羧基,而成为7-氨基头孢烷酸)7-aminocephalosporanicacid熏7-ACA雪。头孢烷是由四元环的β-内酰胺和六元环的氢化噻嗪骈合而成的,由于β-内酰胺环张力较大,其中羰基和氮原子上的孤对电 (A) Overview Cephalosporins antibiotics (Cephalosporins snow cedar nucleus cephalosporanic acid, at the same time have the amino at 7, both in the carboxyl, which became 7-aminocephalosporanic acid) 7-aminocephalosporanicacid smoked 7- ACA snow. Cephalosporin is a four-membered ring of β-lactam and six-membered ring of hydrogen thiazide 骈 together, due to β-lactam ring tension, in which carbonyl and nitrogen atoms on the lone pair