A novel process for the preparation of compounds of formula (I), wherein X is -CH2CH2- or -CH=CH-; R1 is an ester group inert to the reaction conditions; and R is an organic radical having groups which are inert under reducing conditions, by stereoselective reduction of a corresponding compound of formula (II), wherein R, R1 and X are as defined above and one of Z1 and Z2 is oxygen and the other is hydroxy and hydrogen, is disclosed. The process may also be applied to the preparation of compounds of formula (Iu), wherein u is triphenylmethyl (trityl) and Ru is allyl or a radical forming an ester inert under the reaction conditions, which are intermediates in the preparation of some of the compounds of formula (I). A specific embodiment of the above inventive concept is illustrated with the preparation of the compound of formula (Ia) in racemic or optically pure form; in free acid, salt, ester or δ-lactone, i.e. internal ester, form. The compounds of formula (I) are pharmaceuticals, especially antiatherosclerotic, antihyperlipidemic and antihypercholesterolemic agents.