cephamycins , which have a methoxy group at the 7 alpha position of their cephalosporin nuclei , were highly stable against hydrolysis by a beta-lactamase purified from a clinical isolate of morganella morganii , whereas their 7 alpha-h analogs were rapidly hydrolyzed by the enzyme .
C0007736
cephamycins
C3536856
cephalosporin