Biosynthesis of cantharidin: evidence for the specific incorporation of C-4 and C-11′ of farnesol

Abstract

(E,E)-[11′,12-³H₂,2,4-¹⁴C]farnesol is specifically incorporated into cantharidin as shown by use of a new degradation involving a Diels–Alder/retro-Diels–Alder sequence; the incorporation of (E,E)-[11′-³H, ¹⁴C,2-¹⁴C]-farnesol (14) into cantharidin proceeds with 47%³H-retention whereby the 11′-¹⁴C label is randomised at C-9 and C-11 in cantharidin and the ratio [2-¹⁴C]/[11′-¹⁴C] of (14) is retained indicating an intramolecular conversion of farnesol into cantharidin.