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Enantioselective Construction of Highly Functionalized Indoloquinolizines—congeners to Polycyclic Indole Alkaloids
Author(s) -
Lock Ralf,
Waldmann Herbert
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030122
Subject(s) - enantioselective synthesis , indole test , chemistry , derivatization , ring (chemistry) , stereochemistry , lewis acids and bases , alkaloid , organic chemistry , combinatorial chemistry , catalysis , high performance liquid chromatography
Indolo[2,3‐ a ]quinolizines have been prepared in enantiomerically pure form by a very short and efficient synthetic sequence consisting of a) formation of imines of tryptophan esters, b) their enantioselective reaction with substituted silyloxydienes mediated by a chiral or an achiral boron Lewis acid, and c) subsequent ring closure initiated by conversion of the generated vinylogous amides into vinylogous imidoyl chlorides. With this strategy various substituents can be incorporated directly into the 1‐position of the heterocyclic framework of complex indole alkaloids by the choice of an appropriate silyloxydiene, so that subsequent derivatization of the alkaloid precursor at this position is rendered unnecessary.