A new sesquiterpene with a specialized [4,4] bicyclononane skeleton from the marine-derived fungus Metarhizium sp. P2100

Abstract

An oxidized 5/5/6 tricyclic sesquiterpene with a new 6-isopropyl-1,2,9-trimethyl-spiro [4.4]nonane carbon skeleton, metarhizane A (1), was isolated from a rare marine derived fungus Metarhizium sp. P2100. Its structure and the absolute configurations were assigned by interpretation of a combination of spectroscopic data and X-ray diffraction. This is the first example with a spiro [4,4] nonane core among the sesquiterpene skeletons. A plausible biosynthetic pathway for metarhizane A (1) initiated from farnesyl diphosphate (FPP) was predicted and discussed. The above results suggested that this marine-derived fungus has the potential to produce novel skeletons.