The aim of the current work is development of the novel methods for the selective reduction of the double bond of lactone ring in 3-substituted 2-oxo-2,5-dihydrofurans and 2-oxo-5,6-dihydropyrns, as well as the synthesis of new derivatives of unsaturated -lactones on the basis of relatively accessible compounds of butenolide class, with the aim of searching for the biological activity among the synthesized structures.Two reducing systems -"magnesium-methanol" and "sodium borohydride-triethylamine" - are proposed for the selective reduction of C=C double bond of the lactone ring.