Dragmacidin E synthesis studies. Preparation of a model cycloheptannelated indole fragment. Journal   Organic letters. Citation   Org Lett. 7(24):5449-52 Publication date   2005 Nov 24 Authors   Feldman KS Ngernmeesri P Grant agencies   National Institute of General Medical Sciences Grants   NIGMS GM35727 Abstract   [reaction: see text] The conversion of N-2,2-dichloropropionyl indole methyl ester into a tetracyclic cycloheptannelated indole model compound for the synthesis of dragmacidin E was accomplished in 10 steps. Key reactions include a Witkop cyclization to fashion a C-C bond at C(4) of the indole nucleus and a subsequent Dieckmann cyclization to deliver the desired cycloheptanoid ring.