Einbauversuche mit (3H und 14C)-doppelmarkiertem Farnesol in Cantharidin. 5. Mitteilung zur Biosynthese des Cantharidins

Incorporation experiments with (³H and ¹⁴C) doubly labelled farnesols into cantharidin After injection of 11′, 12-³H]-7-¹⁴C]-farnesol or 11′, 12-³H]-5,6-¹⁴C]-farnesol, the ³H-label is located specifically in the C(9)-methyl-group of cantharidin, whereas the ¹⁴C-labelling pattern follows an incorporation via acetic acid (Scheme 4). C-Atoms 5, 6 and 7 from the middle part of the farnesol molecule are utilized for cantharidin biosynthesis to an extent that is about 2.1–11% of the incorporation rate of the methyl groups C(11′) and C(12), depending on the position of the ¹⁴C-label in farnesol. These results confirm our earlier hypothesis 1] that the C₁₀-molecule cantharidin is biosynthesized from the C₁₅-precursor farnesol which is cleaved between C(1)–C(2), C(4)–C(5), and C(7)–C(8). The synthesis of 7-¹⁴C]-farnesol and of 5,6-¹⁴C]-farnesol is described.