Biosynthesis of diisocyanoadociane, a novel diterpene from the marine sponge Amphimedon sp. Crystal structure of a monoamide derivative

Abstract

Sodium [¹⁴C] cyanide is efficiently incorporated into diisocyanoadociane [1,8-di-isocyano-1,2,5,8-tetramethylperhydropyrene, (1)], the major metabolite of the haplosclerid sponge Amphimedon sp. It is established by stepwise chemical degradation that the radiolabel is associated with the two isocyanide carbons. Zinc [¹⁴C] cyanide and isobutyraldehyde [¹⁴C] cyanohydrin are effective precursor alternatives to sodium [¹⁴C] cyanide and more suitable for use in stable isotope study. Attempts to demonstrate an amino acid origin of the cyanide utilised by Amphimedon sp. include tracer studies with [U-¹⁴C] alanine, [2-¹⁴C]glycine, [U-¹⁴C]leucine and [guanidine-¹⁴C]arginine; none of these precursors were used for isocyanide synthesis. Single X-ray crystallographic structure analysis of a p-bromobenzamide degradation product (17) established that the absolute configuration for diisocyanoadociane is (1R,2R,3aS,5S,6R,8S,8aS,10aS,10bS,10cS).