A solution of ethyl 4-[3-pentyl-3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalen-2-yl)-ureido]-benzoate (37) (360 mg, 0.77 mmole) in 10 mL ethanol was treated with 430 mg of potassium hydroxide in 2 mL water. THF (2 mL) was added and the mixture was heated to 45° C. for two hours. The reaction mixture was diluted with 10 mL water, the pH adjusted to 2 with concentrated HCl and then extracted with three 25 mL portions of ethyl acetate. The combined organic extracts were dried over MgSO4, filtered and concentrated in vacuo, to give a pale yellow solid. The product was purified by trituration in pentane and 280 mg of 4-[3-pentyl-3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalen-2-yl)-ureido]-benzoic acid (27) were obtained as a white solid. M.P.: 184-186° C.
