Poecillastrin H, a Chondropsin-Type Macrolide with a Conjugated Pentaene Moiety, from a Characella sp Marine Sponge

Poecillastrin H (1), a chondropsin-type macrolide with a conjugated pentaene moiety, was isolated from the Characella sp. marine sponge. The planar structure of 1 was elucidated by analysis of spectroscopic data. The absolute configuration of the beta-hydroxyaspartic acid residue (beta-OHAsp) was determined to be D-threo by Marfey's analysis, and the mode of lactone ring formation through the OHAsp residue was determined by chemical degradation. Poecillastrin H was extremely sensitive toward light and showed potent cytotoxic activity against 3Y1 cells with an IC50 value of 4.1 nM.