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  • Conjugate addition of 2- and 4-pyridylcuprates: an expeditious asymmetric synthesis of natural (-)-evoninic acid.

Conjugate addition of 2- and 4-pyridylcuprates: an expeditious asymmetric synthesis of natural (-)-evoninic acid.

Organic letters (2007-02-10)
Alan C Spivey, Lena Shukla, Judy F Hayler
ABSTRACT

[reaction: see text] The scope and limitations of the conjugate addition of 2- and the first 4-pyridyl Gilman homocuprates to various alpha,beta-unsaturated Michael acceptors are delineated. The conjugate addition of the cuprate of 2-bromo-3-methylpyridine to (E)-methyl crotonate then diastereoselective enolate alkylation and lipase-mediated enantioselective ester hydrolysis have enabled an efficient four-step first asymmetric synthesis of the Celastraceae sesquiterpenoid esterifying ligand (-)-(1'S,2'S)-evoninic acid.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Potassium bis(trimethylsilyl)amide solution, 0.5 M in toluene
Sigma-Aldrich
2-Bromo-3-methylpyridine, 95%