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1,2‐Asymmetric Induction in Diastereoselective Zwitterionic Aza‐Claisen Rearrangements: Key Steps in Optically Active Alkaloid Synthesis
Author(s) -
Heescher Carolin,
Schollmeyer Dieter,
Nubbemeyer Udo
Publication year - 2013
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/ejoc.201300389
Subject(s) - chemistry , pyrrolizidine , indolizidine , asymmetric induction , optically active , pyrrolizidine alkaloid , claisen rearrangement , alkaloid , stereochemistry , enantioselective synthesis , total synthesis , lactam , organic chemistry , catalysis
The zwitterionic aza‐Claisen rearrangement of optically active N ‐allylpyrrolidines and α‐phenoxyacetyl fluorides proceeds with complete simple diastereoselectivity (internal asymmetric induction) and complete 1,2‐asymmetric induction to generate a new C–C bond adjacent to a chiral C‐ N ‐Boc functionality. The resulting γ,δ‐unsaturated amides were cyclised to give the corresponding pyrrolizidinones, which enabled the determination of the relative configuration of the stereotriads. Vinyl group degradation and a final lactam reduction gave an optically active analogue of (+)‐petasinine (a pyrrolizidine alkaloid). Furthermore, the stereotriad‐containing amides should be useful key intermediates for the total synthesis of optically active elaeocarpin (an indolizidine alkaloid).