0.49 ml (6.8 mmol) of thionyl chloride is added, at 0° C., to a solution of 1.01 g (3.4 mmol) of phenylmethyl 3-carboxy-2-(phenylmethyl)-1-propanoate in 15 ml of dichloromethane, followed by two drops of N,N-dimethylformamide. After 2 h at room temperature, the mixture is evaporated to dryness and the residue is dissolved in 25 ml of dichloromethane. The solution is cooled to 0° C. and then a solution of 0.81 g (3.4 mmol) of 5,6-dihydro-4H-thieno[3,4-c]pyrrole trifluoroacetate and 1.42 ml (10.2 mmol) of triethylamine in 25 ml of dichloromethane is added. After 16 h at room temperature, 25 ml of water are added, and the organic phase is decanted off, washed with a saturated sodium chloride solution and then dried over sodium sulphate and evaporated to dryness. The residue is chromatographed on a silica gel with the aid of the eluent mixture ethyl acetate/hexane 3/7. 0.52 g of a white solid is obtained.
