Access to Enantiopure 2,5‐Diaryltetrahydrofurans – Application to the Synthesis of (–)‐Virgatusin and (+)‐Urinaligran

The diastereoselective Mn III ‐promoted radical addition of β‐oxoesters 1 onto N ‐cinnamoyloxazolidinones 2 afforded 2,3‐dihydrofurans 3 . After catalytic hydrogenation of the C=C bond, followed by reductive removal of the chiral auxiliary, the resulting enantiopure tetrahydrofurans 5 were transformed in two steps into naturally occurring (–)‐virgatusin and (+)‐urinaligran and two other, nonnatural, tetrasubstituted THF lignans. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)