The present invention provides optically active esters of 7-substituted 3,5-difunctionalized 6-heptenoic acids represented by the following formula: ##STR1## wherein R is a substituted or unsubstituted aromatic group, a substituted or unsubstituted heteroaromatic group or a substituted vinyl group;Ar is a condensed aromatic group;X.sup.1 and Y.sup.1 are not the same and each is a hydrogen atom or a hydroxyl group, or may be combined to represent an oxygen atom which forms a carbonyl group together with the carbon atom to which X.sup.1 and Y.sup.1 are attached; andX.sup.2 and Y.sup.2 are not the same and each is a hydrogen atom or a hydroxyl group, or may be combined to represent an oxygen atom which forms a carbonyl group together with the carbon atom to which X.sup.2 and Y.sup.2 are attached,or enantiomers thereof.The present invention further provides processes for preparing the above optically active esters and 7-substituted (3R, 5S, 6E)-3,5-dihydroxy-6-hepten-1,5-olides.These esters are useful as synthetic intermediates for preparing the above lactones having an inhibitory activity of HMG-CoA reductase as well as a sex attractant pheromone of beetles, endo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane.