9.3 g of (2-adamantan-1-yl-4-bromo-phenoxy)-tert-butyl-dimethylsilane were dissolved in 120 ml of absolute tetrahydrofuran and treated dropwise at -78° C. with 15.5 ml of a 1.6 molar solution of n-butyl-lithium in hexane. After stirring at -78° C. for 1.5 hours, a vigorous stream of carbon dioxide was introduced for one hour. Subsequently, the reaction mixture was firstly poured into ice-cold, saturated, aqueous ammonium chloride solution, acidified cautiously to pH 3 with cold 2N hydrochloric acid and extracted with ethyl acetate. After washing once with water, drying over sodium sulfate and evaporation there was obtained a white, crystalline mass which was recrystallized from ethyl acetate and gave 7 g of 3-adamantan-1-yl-4-(tert-butyl-dimethyl-silanyloxy)-benzoic acid, m.p. 250°-252° C.
