Iodinated indole alkaloids from Plakortis simplex -: New plakohypaphorines and an evaluation of their antihistamine activity

Three new iodinated tryptophan derivatives, plakohypaphorines D-F (4-6), have been isolated from the Caribbean sponge Plakortis simplex. Their structures have been determined by applying spectroscopic methods and microwave-assisted selective dehalogenation. Compound 5 is the first naturally occurring triiodinated indole, while compound 6 is a unique metabolite because it possesses both chlorine and iodine atoms on the indole nucleus. We have evaluated the antihistamine activity of the whole series of plakohypaphorines A-F, but only the diiodinated analogues proved to be active: they display a specific antagonism of the noncompetitive type. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.