Biosynthetic origin of [7.7]paracyclophanes from cyanobacteria

Abstract

The biosyntheses of nostocyclophane D ( 1) and cylindrocyclophane D ( 2) have been investigated by the administration of sodium [1,2- 13C 2]acetate, sodium [1- 13C, 2H 3]acetate, sodium [2- 13C, 2H 3]acetate, sodium [ 2H 3]acetate, sodium [1- 13C, 18O 2]acetate, sodium [2- 13C, 18O 2]acetate, l-[methyl- 13C]methionine, and l-[methyl- 13C, 2H 3]methionine to cultures of the cyanobacteria Nostoc linckia and Cylindrospermum licheniforme, respectively. The isotopically labeled compounds produced by these feeding experiments indicate that the structural skeletons of these [7.7]paracyclophanes are polyketides that have been constructed by dimerization of acetate-derived nonaketides. Acetate has also been identified as the source of the branched methyl groups in cylindrocyclophane D.