Structure and reactivity of illudins

Abstract

An X-ray crystallographic analysis of illudin S, an anitumor sesquiterpene from Omphalotus illudens, has been carried out. Crystal data: C15H20O4, orthorhombic, space group P21212, a = 15.103(5), b = 10.574(5), c = 8.917(3) Å, Z = 4, F(000) = 568, λ (Cu) = 1.54184 Å. Final residual index R = 0.037. Interatomic distances indicate nonbonded repulsive interactions between the methylenes of the cyclopropane ring and the adjacent tertiary hydroxyl and methyl groups. Relief of this interaction may explain the ready isomerization of illudins to isoilludins. Molecular mechanics calculations show isoilludin M to be ∼5 kcal/mol more stable than illudin M in agreement with this postulate. Reaction of illudin M with dilute HCl gives two chloroindantriols by nucleophilic attack of chloride on the cyclopropane ring leading to a quinoid intermediate which is trapped by solvent. mudins can thus act as bifunctional alkylating agents. © 1989.