Biosynthesis of the verrucarins and roridins. Part 4. The mode of incorporation of (3R)-((5R)-5-3H)-mevalonate into verrucarol. Evidence for the identity of the C(11)-hydrogen atom of the trichothecane skeleton with the (5R)-hydrogen atom of (3R)-mevalonic acid.

Incorporation of (3R)-[(5R)-5-³H]-mevalonate into verrucarin followed by hydrolyses to verrucarol (2) and transformation of the latter to the spirolactol 5 and the spirolactone 6 successively, demonstrate the identity of the C(11)-hydrogen of the trichothecane skeleton with the 5-‘pro-R’ hydrogen atom of (3R)-mevalonate.