ORGN 299 |
| We have previously reported a highly diastereo- and enantioselective strategy for cycloaddition of nitrile imines to olefins bearing a variety substituents at the beta-position. We are interested in developing enantioselective nitrile imine cycloadditions with dipolarophiles containing additional substitution at the alpha-position. The resulting products contain a tert-alkylamino quaternary chiral center at the 5-position of the dihydropyrazole ring. The ability to control the absolute configuration of this quaternary chiral center is critical to the synthesis of a number of tert-alkylamino hydroxy carboxylic acid natural products. We now wish to report a highly regio-, diastereo-, and enantioselective cycloaddition of nitrile imines to alpha, alpha-disubstituted and alpha, alpha, beta-trisubstituted dipolarophiles as a methodology for formation of the requisite chiral quaternary center. Application of the new cycloaddition methodology in approaches to the manzacidin alkaloids will be presented.
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Asymmetric Reactions and Syntheses
1:00 PM-5:00 PM, Monday, 11 September 2006 Moscone Center -- Room 131, Oral
Division of Organic Chemistry |
