Cephamycin 3-hydroxy

To summarise, cephalosporins are produced by ring expansion of penicillin N to deacetoxycephalosporin C which is then oxidised to deacetylcephalosporin C. In C. acremonium, this last compound is acet-ylated to cephalosporin C. In 5. clavuligerus deacetylcephalosporin C is transcarbamoylated then converted to the 7a-methoxy derivative cephamycin C, probably via a 7a-hydroxy intermediate. Cephalosporin biosynthesis is shown diagramatically in Fig. 8. 

The only natural derivatives of a-hydroxy-a-amino acids found to date are the 7-methoxycephalosporins (1) (cephamycins) (271), an important class of therapeutically valuable antibiotics. 

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