A highly efficient stereospecific synthesis of the biotin precursor (3aα, 6aα)-1, 3- dibenzylhexahydro-1H-thieno [3, 4-d] imidazol-2 (3H)-one 1, 1-dioxide (6) is reported, by the cyclisation of the urea (5), which was obtained from the amine (4),(4) itself being prepared by the reaction of the dibromide (2) with benzylamine.
