2-(3-Benzyloxy-5-trifluoromethyl-phenyl)-8-[2-(4-tert-butoxycarbonyl-2-methyl-phenyl)-ethanesulfonyl]-4-oxo-1,3,8-triaza-spiro[4.5]dec-1-ene-3-carboxylic acid tert-butyl ester (1.11 g, 1.41 mmol) was dissolved in ethyl acetate (45.0 ml)-THF (15.0 ml). Pd—C (222 mg) was added and the mixture was stirred at room temperature and for one hour in a hydrogen atmosphere. After completion of the reaction, the black solid was filtered off through celite, and the filtrate was concentrated under reduced pressure to give 8-[2-(4-tert-butoxycarbonyl-2-methyl-phenyl)-ethanesulfonyl]-2-(3-hydroxy-5-trifluoromethyl-phenyl)-4-oxo-1,3,8-triaza-spiro[4.5]dec-1-ene-3-carboxylic acid tert-butyl ester as an amorphous (1.01 g, 100%).
