Disclosed is a process for producing novel optically active titanium alkoxide complexes which are excellent in catalytic activity and enantio-selectivity in carbon-carbon bond forming reactions (for example, Ene reaction, hetero-Diels-Alder reaction, Aldol reaction) and have high stability. The present process comprises reacting (R),(S),(RS)-catalysts or mixtures thereof selected from among optically active or racemic titanium alkoxide complexes represented by the following general formula (1), etc.: ##STR1## wherein R.sup.1 represents a methyl, lower alkoxy or trihalogeno group; R.sup.2 represents a hydrogen or halogen atom; R.sup.3 represents a hydrogen atom or a methyl group; and R.sup.4 represents a lower alkyl group, or R.sup.1 and R.sup.2 may form together a cyclo ring;with chiral activators [(R),(S),(RS)-diols or mixtures thereof, but excluding reactions between a racemic modification and another racemic modification] to thereby activate exclusively one of the enantiomers.