Premium
Highly Stereoselective trans Addition of π‐Type Nucleophiles to a Bicyclic N ‐Acyliminium Ion – Application to the Synthesis of Indolizidine and Pyrrolizidine Alkaloids
Author(s) -
Dhimane Hamid,
VanucciBacqué Corinne,
Hamon Louis,
Lhommet Gérard
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199809)1998:9<1955::aid-ejoc1955>3.0.co;2-u
Subject(s) - pyrrolizidine , chemistry , enantiopure drug , indolizidine , nucleophile , stereoselectivity , stereochemistry , lewis acids and bases , bicyclic molecule , adduct , carbocation , enantioselective synthesis , organic chemistry , alkaloid , catalysis
Enantiopure bicyclic 5‐ethoxytetrahydropyrrolo[1,2‐c]oxazol‐3‐one 1b was prepared in two steps from the known tosylate 4 , which is readily available from ( S )‐pyroglutamic acid. Trapping of the N ‐acyliminium ion ( I ), generated in situ from 1b in the presence of Lewis acid, with various silylated π‐type nucleophiles gave rise selectively to trans adducts 2 . The usefulness of this stereoselective access to trans ‐2,5‐disubstituted pyrrolidines was illustrated by formal syntheses of 3,5‐disubstituted indolizidine toxins, starting from 5‐allyltetrahydropyrrolo[1,2‐c]oxazol‐3‐one 2a . Moreover, an enantiodivergent synthesis of the pyrrolizidine alkaloids (+) and (–)‐xenovenine was achieved starting from the same chiral building block 2a .