Approaches to 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane lignans via asymmetric synthesis of dihydro- and tetrahydro-furan derivatives

Cyclisation of chiral non-racemic phenylsulphonylvinyl epoxy ethers, produced using the Sharpless epoxidation reaction, has been used to prepare a series of enantiomerically enriched 2-aryl-4-(α-hydroxybenzyl)-4,5-dihydrofuran derivatives. Reduction of these compounds using triethylsilane and BF3–diethyl ether gave the corresponding tetrahydrofuran derivatives stereoselectively. Attempts to convert either the dihydro- or tetrahydro-furan derivatives into lignans belonging to the 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane series have so far proved unsuccessful.