DIASTEREOSELECTIVE SPIROCYCLIZATION OF C-(ALKYLOXYCARBONYL)FORMIMINES OF 2-SUBSTITUTED 1H-INDOLE-3-ETHANAMINES (= TRYPTAMINES) - BASIC STUDIES .5. INDOLES, INDOLENINES, AND INDOLINES

C‐(Alkoxycarbonyl)formimines of type 15–18 were derived from the 2‐substituted tryptamines 2, 9, 10, and 11 and transformed with tosyl chloride into tricyclic 3‐spiroindoles of types 19–22 (Scheme 3). The influence of the homochiral alkoxy moieties A–D on the stereochemical outcome of this reaction was studied. Good‐to‐excellent diastereoselectivities were observed with the (−)‐8‐(phenylmenth‐3‐yl)oxy group (B) as homochiral auxiliary. The structures of the tricycles 4, (2′R,3S)‐19B, and (2′S,3R)20C were established by X‐ray analysis, the structures of the others by NOE and CD studies, and by chemical correlation. Possibilities to explain the steric course of the spirocyclizations are discussed. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim