Viridin, Wortmannin and their Relatives

The furan ring of these metabolites, which is subject to the electron-withdrawing effect of the carbonyl groups at C-3 and C-7, is very sensitive to nucleophilic addition. The addition of biological nucleophiles to this centre has been associated with the biological activity of these compounds. 

The labelling pattern of viridin biosynthesized from [2- C]mevalonic acid and of wortmarmin biosynthesized from l,2- C2]acetate was consistent with a triterpenoid/steroidal origin. More detailed studies with demethoxyviridin biosynthesized from [1- C]-, [l,2- C2]-acetate, [2- C]- and [5- C]mevalonate and on the location of the hydrogen atoms originating from acetate and the 2-, 

4- and 5-positions of mevalonate defined the isoprene units and were again consistent with the triterpenoid origin of these metabolites. The extra carbon atom of the furan ring at C-4 was shown to come from the C-4(3 methyl group of a proto-lanosterol precursor. The retention of three deuterium labels from 

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