A novel oxotitanium complex represented by general formula (I) is disclosed: ##STR1## wherein R.sup.1 and R.sup.2 may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a halogen atom, a phenyl group, a substituted phenyl group, a trialkylsilyl group, a monoalkyldiphenylsilyl group, a dialkylmonophenylsilyl group, a triphenylsilyl group, a substituted triphenylsilyl group, or a lower alkoxycarbonyl group, provided that R.sup.1 and R.sup.2 may be bonded to each other to form a hydrocarbon ring or a substituted hydrocarbon ring in cooperation with the carbon atoms to which R.sup.1 and R.sup.2 are bonded; R.sup.3 and R.sup.4 may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a benzoyl group, a benzenesulfonyl group, or a halogen atom, provided that R.sup.3 and R.sup.4 may be bonded to each other to form a hydrocarbon ring or a substituted hydrocarbon ring in cooperation with the carbon atoms to which R.sup.3 and R.sup.4 are bonded; and n is 1 or 2. The novel oxotitanium complex is useful as an asymmetric reaction catalyst. A process for producing a .beta.-hydroxy ketone or an .alpha.-hydroxy carboxylic acid ester in the presence of the novel oxotitanium complex is also disclosed.