Formation of natural thiophene derivatives from acetylenes by tagetes patula

Jente, R.; Olatunji, G.A.; Bosold, F.

Phytochemistry (Oxford) 20(9): 2169-2176


ISSN/ISBN: 0031-9422
DOI: 10.1016/0031-9422(81)80108-2
Accession: 005480949

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Six 3H-labeled thiophene derivatives were synthesized and their emulsions were applied to whole plants of T. patula. From the root extracts, naturally occurring 2,2':5',2"-terthiophene and 4-[2,2'-bithiophen-5-yl]-but-3-yn-1-ol were isolated and investigated for radioactivity. The 4 bithiophenyl precursors, 1,1'-bis-[2-ethynyl-thiophene] and its methyl derivative were incorporated into terthiophene, but only the bithiophenyl precursors were converted into bithiophenylbutynol. While 5-(buta-1,3-diynyl)-2,2'-bithiophene and its 5'-methyl derivative are most probably the direct precursors of terthiophene, the 5-(but-3-en-l-ynyl)-2,2'-bithiophene and its 5'-methyl derivative are the precursors of the bithiophenyl-butynol. Incorporation of 1,1'-bis-[2-ethynylthiophene] and 2-[4-(2-thienyl)-buta-1,3-diynyl]-5-methyl-thiophene into terthiophene showed that the enzyme responsible for the thiophene ring formation has low specificity. From the feeding experiments with the methyl group substituted precursors, 5-methyl-terthiophene was trapped as an intermediate. The presence of the methyl group in the 3 types of precursors is obviously not important for further biosynthetic pathways.