A solution of ethyl 4-[3-butyl-3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalen-2-yl)-ureido]-benzoate (11) (131 mg, 0.29 mmole) in 15 mL methanol, 5 mL of THF and 5 mL of water was treated with 62 mg of lithium hydroxide (5 eq.) and stirred at room temperature for eight hours. The mixture was concentrated in vacuo and the residue was acidified with concentrated HCl solution. The mixture was then extracted with three portions of 20 mL of ethyl acetate. The combined organic extracts were dried over MgSO4, filtered and concentrated in vacuo to give a yellow solid which was purified by flash chromatography (SiO2, 20% ethyl acetate/hexanes+drops of acetic acid) to provide 34 mg (28%) of 4-[3-butyl-3-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalen-2-yl)-ureido]-benzoic acid (5) as a pale yellow solid. MS (EI): (M++1) 423.
