BIOSYNTHETIC STUDY OF CHAETOGLOBOSIN-A - ORIGINS OF THE OXYGEN AND HYDROGEN-ATOMS, AND INDIRECT EVIDENCE FOR BIOLOGICAL DIELS-ALDER REACTION

The biosynthetic origins of the oxygen and hydrogen atoms in the mycotoxin chaetoglobosin A 1 have been investigated by the incorporation of sodium [1-C-13,O-18(2)]-, [1 -C-13,H-2(3)]-acetate and O-18(2) gas into the mycotoxin by using the chaetoglobosin-producing strain Chaetomium subaffine. Considering the results of the P-450 inhibitor experiment, the results obtained from the above experiments support the biogenetic pathway proposed. Attempts at direct conversion of C-14- or C-13-labelled prochaetoglobosin I 2 using whole cells were unsuccessful. Formation of the diastereoisomer 10 of 2 in the retro-Diels-Alder reaction of compound 2 has provided indirect evidence that the plausible precursor hexaene 6 is able to cyclize via [4 + 2]cycloaddition in the biosynthesis of chaetoglobosin A 1.