Synthesis of the 3a-(3-Indolyl)-1,2,3,3a,8,8a-hexahydropyrrolo-[2,3-b]indole Core of Leptosins D-F

Abstract

The Fischer indole reaction of aldehyde and phenyl hydrazine in the presence of zinc chloride smoothly pmvides the core structure of the leptosins D-F in good to excellent yield.Leptosins D-F (1-3) were isolated in 1994 from the culture of a strain of Lepfoshaaeria sp. which itself was isolated from the marine alga Smgnrswn tortile.1These compounds which may arise fmm leptosins A-C (4-6),1,2 isolated from the same broth, by Grob type fragmenation, were found to possess cytotoxic activity against the P-388 lymphocytic leukemia cell line comparable to that of mitomycin c .~ This