Stereoselective synthesis of 2,6-trans-tetrahydropyran via primary diamine-catalyzed oxa-conjugate addition reaction of α,β-unsaturated ketone: total synthesis of psymberin.

The total synthesis of psymberin was achieved employing a readily available chiral epoxide to prepare two of the three subunits in the natural product. The key reaction was a highly stereoselective organocatalytic oxa-conjugate addition reaction of α,β-unsaturated ketone catalyzed by primary diamine for the synthesis of the 2,6-trans-tetrahydropyran embedded in psymberin.