10.

A chiral 1,3,2-dioxaborolane derived from a natural diterpene for asymmetric reduction of prochiral ketones

Diego A. Cifuente and Carlos E. Tonn

INTEQUI-CONICET, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700, San Luis, Argentina.

Abstract: The application of a chiral 1,3,2-dioxaborolane, for the sulfide complex-mediated asymmetric reduction of prochiral ketones at room temperature, are described. The B-methoxy-dioxaborolane was synthesized from 2 a ,3 a -dihydroxycativic acid, a labdane-type diterpene isolated from aerial parts of Baccharis scandens DC. Very good chemical yields (85-97%) and high enantioselectivities (62-96% ee), were obtained.

Keywords: Asymmetric reductions; chiral 1,3,2-dioxaborolane; 2 a ,3 a -dihydroxycativic acid.