Incorporation of Labeled Precursors into A16886B, a Novel β-Lactam Antibiotic Produced by Streptomyces clavuligerus

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Abstract
The incorporation of C-14 from amino acids into A16886B, 7-(5-amino-5-carboxyvaleramido)-7-methoxy-3-carbamoyloxymethyl-3-cephem-4- carboxylic acid, by Streptomyces clavuligerus is reported. As with cephalosporin C biosynthesis by the mold Cephalosporium acremonium , labels from cysteine, valine, and α-amino-adipic acid were incorporated. Unlike cephalosporin C, in A16886B label from lysine was incorporated into the α-aminoadipic acid side chain. Label from methionine- 14 C-methyl was incorporated into the methoxyl group. The relative percentage of incorporation of 3 H and 14 C from doubly labeled cystine suggests the improbability of the C-7 methoxyl group arising from an intermediate containing a double bond between C-6 and C-7.