5‐Substituted Derivatives of the Tricyclic (+)‐Sparteine Surrogate in the Enantioselective Lithiation/Stannylation of an O‐Alkyl Carbamate. Issue 33 (2nd October 2013)

• Record Type: Journal Article
• Authors: Breuning, Matthias; Hein, David
• Is Part Of: European journal of organic chemistry. Issue 33(2013)
• Page Start: 7575
• Page End: 7582
• Publication Date: 2013-10-02
• Subjects: Asymmetric synthesis -- Ligand effects -- Enantioselectivity -- Amines -- Alk­aloids; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201300987
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: 5‐Mono‐ and 5, 5‐disubstituted tricyclic bispidines, derivatives of the known (+)‐sparteine surrogate, have been synthesized in four‐to‐six steps from the natural alkaloid (–)‐cytisine and evaluated as chiral ligands in the enantioselective lithiation/stannylation of an O ‐alkyl carbamate. Structure–selectivity studies revealed that a small 5‐ endo substituent is tolerated, whereas larger 5‐ endo substituents and even small 5‐ exo substituents lead to significantly reduced levels of chirality transfer. Abstract : Novel tricyclic bispidines have been synthesized from the readily available alkaloid (–)‐cytisine and evaluated in the enantioselective lithiation/stannylation of an O ‐alkyl carbamate. Structure–selectivity studies revealed that an increased steric demand at the 5‐ endo position is not favorable.