Cyclic alpha-unsaturated beta-ketoesters undergo cycloaddition with di-and trisubstituted butadienes to give tetrahydro-1-indanone derivatives with up to 93% ee in the presence of a ruthenium catalyst formed by activation of [RuCl2(PNNP)] with (Et3P)PF6 (2 equiv) (PNNP = (1S,2S)-N,N'-bis[o-(diphenylphosphino)benzylidene]cyclohexane-1,2-diamin e). The protocol has been used to prepare the estrone derivative (8R, 13S, 14S)-13-tert-butoxycarbonyl-3-methoxy-7,8,1 2,13,15,16-hexahydro-6H-cyclopenta[a]phenanthren-17(14H)-one as a single diastereoisomer with 85% yield and 99% ee after one crystallization step. Its absolute configuration, which has been determined by X-ray diffraction after reduction to the alcohol and esterification with camphanic chloride, is in agreement with the attack of the diene onto the open enantioface of the beta-keto ester (O-O) in the ruthenium complex [Ru(O-O)(PNNP)](2+), whose X-ray structure has been determined.