A Short Synthesis of (-)-Chokol A

Article abstract of DOI:10.1016/0040-4020(95)00834-U

(-)-Chokol A (10) was prepared in six steps (22 percent overall yield) via conjugate addition of a higher order cyanocuprate to the chiral 2-oxo-cyclopentenecarboxylate 2n.After deprotection by transesterification the enantiomerically pure β-ketoester 5 was obtained which was transformed by α-methylation and subsequent decarbethoxylation to the cyclopentanone derivative 8.Addition of methylcerium dichloride resulted in a mixture of 9a, 9b and 9c (78:16:6), from which the main diastereomer 9a was separated by MPLC.Finally desilylation of 9a achieved (-)-chokol A (10).