General enantioselective synthesis of butyrolactone natural products via ruthenium-SYNPHOS®-catalyzed hydrogenation reactions

Enantioselective syntheses of several paraconic acids have been achieved using catalyzed asymmetric, hydrogenation of beta-keto esters with SYNPHOS (R) as a ligand. This strategy allowed the short synthesis of biologically active (-)-methyleno-lactocin 1, (-)-protolichesterinic acid 2, (-)-phaseoconic acids have been achieved using linic acid 3 and (+)-roccellaric acid 4.