The biosynthesis of antitumor antibiotic cytogenin, 3-hydroxymethyl-6-
methoxy-8-hydroxy-isocoumarin, was studied by feeding C-14- Or C-13-la
beled compounds to culture of the producing organism, Streptoverticill
ium eurocidicum MI43-37F11. C-14-Acetate and C-14-methionine were effi
ciently incorporated into cytogenin as precursors. C-13 NMR studies pr
oved that the carbon skeleton of cytogenin is derived from pentaketide
intermediate due to head-to-tail condensation of five acetate units a
nd methyl group of 6-OCH3 is derived from methionine. It was suggested
that 3-hydroxymethyl and/or 6-methoxy group of cytogenin were metabol
ized by hydroxylation and/or methylation from three intermediates.