post treatment were conducted as in example 4 except that 260 grams of 2 propanol were used instead of 220 grams of 2 propanol and 40 grams of water in example 4 to yield a mixture of 65 grams of 1r 3as 6ar 4 6 dibenzyl 1 3 ethoxypropyl 5 oxohexahydro 1h thieno 3 4 d imidazole and 62 grams of the starting 3as 6ar 4 6 dibenzyl 1 3 ethoxypropylidene 5 oxohexahydro 1h thieno 3 4 d imidazole as an oily material 132 grams of 5 3as 6ar 4 6 dibenzyl 5 oxohexahydro 1h thieno 3 4 d imidazol 1 ylidene pentanoic acid were dissolved in a solution of 450 grams of 2 propanol and 200 grams of water and catalytically reduced with one gram of palladium acetate 1 4 mole percent under a hydrogen pressure of 20 kg cm 2 at a temperature of 70 u00b0 c for three hours after the reaction 0 1 gram of aluminum sulfate and 15 grams of activated carbon were added to the reaction solution and stirred at a temperature of 60 u00b0 c for two hours to flocculate the catalyst which was filtrated to be removed the filtrate was condensed under a reduced pressure to yield 131 grams of 5 1r 3as 6ar 4 6 dibenzyl 5 oxohexahydro 1h thieno 3 4 d imidazol 1 yl pentanoic acid as an oily material purity 98 the compound was left to stand overnight in an refrigerator to be crystallized and recrystallized from 2 propanol and hexane mp 91 u00b0 92 u00b0 c u03b1 d 23 26.