The distribution of acetate-derived oxygens in the tetronic acids of Penicillium multicolor

Abstract

Incorporation of sodium [1-¹³C, ¹⁸O₂]acetate by penicillium multicolor into multicolanic, multicolic, and multicolosic acids(1), (2), and (3), respectively, has given samples which when derivatised and examined by spin echo Fourier transform (S.E.F.T)¹³C n.m.r. spectroscopy show ¹⁸O-induced ¹³C-satellites, confirming the previously proposed biosynthetic pathway involving oxidative fission of the β-ketide derived intermediate 6-pentylresorcylate (8) and establishing that lactonisation of the tetronic acid ring occurs by displacement from the C-1carboxy-group by the C-4 enolic oxygen, rather than by lactol formation.