20.00 g (51.7 mmol) of cholesterol, 2.88 g (25.75 mmol) of 4-dimethylaminopyridine, 6.27 g (62.04 mmol) of triethylamine are dissolved in 100 mL of dichloromethane. 11.92 g (51.7 mmol) of commercial 3,5-dinitrobenzoylchloride dissolved in 50 mL of dichloromethane are added at 0° C. The solution is stirred for 2 h at 0° C. and allowed to stir at room temperature overnight. After 22 hours at room temperature, the reaction mixture is partitioned between dichloromethane and water. The organic phase is washed repeatedly with water, dried over sodium sulfate, filtrated and concentrated under reduced pressure. Crystallization from ethyl acetate:hexane mixture yielded 16.94 g (56%) of (3-β)-cholest-5-en-3-yl 3,5-dinitrobenzoate as yellowish crystals.
