Cephalosporin C biosynthesis; stereochemistry of the incorporation of D,L,D-α-aminodipoyl-cysteinyl-(3S)-[2-2H,4-13C]valine into β-lactam compounds

Abstract

Incubation of D,L,D-α-Aminodipoyl-cysteinyl-(3S)-[2-²H,4-¹³C]valine (8b) with partially purified isopenicilln N synthetase fromCephalosporium acremonium CO 728 gave stereospecifically labelled (2R,3S)-[2′-¹³C,3-²H]penicillin N(9): further incubation of the product with partially purified deacetoxycephalosporin C/ deacetylcephalosporin C synthetase from C. acremonium CO 728 gave ring expanded products in which the ¹³C-label was incorporated exclusively into the C3′-exocyclic positions.