A rationally designed chiral auxiliary for hydroxyalkyl radicals leads to exceptional rho-stereocontrol

Substitution of a t-butyl group at C-6 of the THP ring results in a chiral auxiliary that exerts exceptional stereocontrol in radical addition reactions. For example, radical 2c adds to 2-nitropropene at -78 degrees C to give, after reductive hydrolysis, the protected aldol 4c with a diastereoselectivity of 35/1. Good selectivity (ds = 8/1) is even observed when the reaction is conducted at ambient temperature. (C) 1997 Elsevier Science Ltd.