HALICHONADINS M-Q, SESQUITERPENES FROM AN OKINAWAN MARINE SPONGE HALICHONDRIA SP.

Four new dimeric sesquiterpenes, halichonadins M-P (1-4), and one new sesquiterpene, halichonadin Q (5), were isolated from an Okinawan marine sponge Halichondria sp. The sesquiterpenes have eudesmane skeleton in common Halichonadin M (1) is a symmetrical dimer linked to a nitrilotriacetic acid fragment through amide bonds. Halichonadin N (2) is a structurally unique dimeric sesquiterpene connected via a pyrrolidine unit, while halichonadins 0 (3) and P (4) have linker moieties consisting of a piperidine unit. Halichonadin Q (5) is a sesquiterpene possessing a pyrrolidine unit. The structures of 1-5 were elucidated by spectroscopic analysis. Halichonadin 0 (3) showed antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, and Trichophyton mentagrophytes.