Synthesis of the Pyrrole-Imidazole Alkaloid Sventrin from the Marine Sponge Agelas sventres

Gregor Breckle, Kurt Polborn, and Thomas Lindel Ludwig-Maximilians-Universität München, Department of Chemistry, Butenandtstr. 5Ð13, D-81377 Munich, Germany Reprint requests to Prof. Dr. Th. Lindel. Fax int: +(0)89/2180-7-7734. E-mail: [email protected] Z. Naturforsch. 58b, 451Ð456 2003; received February 17, 2003 The marine pyrrole-imidazole alkaloid sventrin (1) and the hitherto unknown dehydrooroidin (3) have been synthesized stereoselectively via alkyne intermediates. The pathways start from a 2-azido-4-alkynylimidazole which can be chemoand stereoselectively reduced to the corresponding amino alkene using NaAlH2(OCH2CH2OMe)2 (Red-Al) or, alternatively, to the amino alkyne. Selective removal of simultaneously present Boc or trityl protecting groups was possible employing either p-TsOH or acetic resp. formic acid.