Document Detail

Electrochemical synthesis and chemistry of chiral 1-cyano-tetrahydroisoquinolines. An approach to the asymmetric syntheses of the alkaloids (-)-crispine A and its natural (+)-antipode.
MedLine Citation:
PMID:  22017231     Owner:  NLM     Status:  Publisher    
The stereoselective convergent total syntheses of both enantiomers of the tetrahydroisoquinoline (THIQ) alkaloid crispine A are described. The THIQ precursors (-)-6 (90:10 dr) and (-)-11 (85:15 dr) were prepared from the alkylation-reduction sequence of a common alpha-amino nitrile (+)-4 derivative which has been conveniently prepared by anodic cyanation. Elaboration of the pyrrolidine ring of the title compound was cleanly achieved by two efficient ring closures methods involving a) the displacement of a halogen atom b) the formation of a cyclic iminium cation to afford (-)-crispine A in 90% and 85% yields, respectively. A crystallization of enantioenriched (-)-crispine A (90:10 er) with one equivalent of (-)-DBTA afforded the tartrate salt (-)-14 (greater than or equal to 98:2 dr) in 81% yield. The absolute S configuration of (-)-crispine A was simply deduced from examination of the X-ray data of tartrate salt (-)-14. Likewise, the natural (+)-crispine A was prepared in 7 work-up steps in an overall 30% yield and reciprocal crystallization with (+)-DBTA afforded the enantiomeric tartrate salt (+)-14 in a greater than or equal to 98:2 dr. Both enantiomers of crispine A were liberated from their respective DBTA salts in greater than or equal to 98:2 er's which were determined by proton and carbon NMR spectroscopy, utilizing (R)-(+)-tert-butylphenylphosphinothioic acid (+)-15 as chiral solvating agent.
Fadila Louafi; Julie Moreau; Saurabh Shahane; Stéphane Golhen; Thierry Roisnel; Sourisak Sinbandhit; Jean-Pierre Hurvois
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-10-21
Journal Detail:
Title:  The Journal of organic chemistry     Volume:  -     ISSN:  1520-6904     ISO Abbreviation:  -     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-10-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985193R     Medline TA:  J Org Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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