Synthesis of biomimetic precursors of isovelleral analogues.

Based on how the mushroom Lactarius vellereus converts an inactive precursor into the cytotoxic dialdehyde isovelleral (1) via a cyclic enol ether, as part of a binary chemical defense system that protects the fruit bodies against parasites, a synthetic way to obtain analogous dialdehydes masked in the same way has been developed. As isovelleral analogues (e.g. 2 and 3) possess extremely potent cytotoxic activity, but display low selectivity as their biological activity is linked to their reactivity, suitably masked isovelleraloids that are converted to the corresponding dialdehyde under specific conditions, may constitute a way to utilize these potent compounds. Specifically, compounds 4 and 5, biomimetic precursors of the isovelleral analogues 2 and 3, but trapped as the stable methyl acetals, have been prepared.