Biosynthesis of theobroxide and its related compounds, metabolites of Lasiodiplodia theobromae

2H and 13C NMR analyses of theobroxide 1, a potato-tuber inducing substance, and its carbonyldioxy derivative 2, produced by Lasiodiplodia theobromae in the presence of 2H and 13C-labeled acetates clarified the tetraketide origin of 1 and 2 and the incorporation of the carboxy carbon of acetate into a carbonyl carbon in 2. Administration of 13C labeled acetates ([1- 13C], [2- 13C] and [1,2- 13C 2] to Lasiodiplodia theobromae showed the tetraketide origins of both theobroxide, a potato-tuber inducing substance { 1, (1 S, 2 R, 5 S, 6 R)-3-methyl-7-oxa-bicyclo[4.1.0]hept-3-en-2,5-diol}) and its carbonyldioxy derivative { 2, (1 S, 4 R, 5 S, 6 R)-7,9-dioxa-3-methyl-8-oxobicyclo [4.3.0]-2-nonene-4,5-diol}. The incorporation of acetate-derived hydrogen into 1 and 2 was studied using [2- 2H 3, 2- 13C]acetate. Three and one deuterium atoms were incorporated at one methyl and epoxy carbons, respectively. The observed loss of deuterium atoms from the methyl group suggests a considerable amount of exchange from the methyl group of [2- 2H 3, 2- 13C]acetate during biosynthesis of 1 and 2. Incorporation of [1- 13C]- and [1,2- 13C 2]acetates indicates the carbonyl carbon of the carbonyldioxy derivative is derived from the carboxy carbon of the precursor.