derivatives of 4 - 4.5 - dihydro oxofuran - 2carbons ure, particularly for use as a hypolipidaemische agents, methods for their production, pharmaceutical compositions containing them, in the manufacture of angefuehrten derivatives usable tetrahydropyran - 2,3,5 tri one and a process for the production of these tetrahydropyran - 2,3,5 - trione.