Stereoselective Conjugate Addition Directed by an Enantiomerically Pure Ketal. Preparation of the Cyclohexanone Fragment of N-Methylwelwitindolinone C Isothiocyanate

Joseph P. Konopelski; Hongbo Deng; Kai Schiemann; Joseph M. Keane; Marilyn M. Olmstead

doi:10.1055/s-1998-1886

Synlett 1998; 1998(10): 1105-1107
DOI: 10.1055/s-1998-1886

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Stereoselective Conjugate Addition Directed by an Enantiomerically Pure Ketal. Preparation of the Cyclohexanone Fragment of N-Methylwelwitindolinone C Isothiocyanate

Joseph P. Konopelski^* , Hongbo Deng, Kai Schiemann, Joseph M. Keane, Marilyn M. Olmstead

^*Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064; Fax 408-459-2935; E-mail: joek@chemistry.ucsc.edu

Abstract

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A cyclohexanone intermediate to be employed in the synthesis of the marine natural product N-methylwelwitindolinone C isothiocyanate has been prepared. The synthesis is diastereoselective for the production of the C12 quaternary center, which is obtained via a conjugate addition reaction directed by an adjacent chiral, nonracemic ketal. A single crystal X-ray analysis of a derivative of the final product established the absolute stereochemistry at C12.

conjugate addition - chiral ketal - cuprates - marine natural products - alkaloids

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