To a solution of N-(t-butoxycarbonyl)glycine (marketed product) (14.7 g; 84.0 mmol) and Et3N (8.50 g; 11.6 ml; 84.0 mmol) in THF (400 ml), at 0° C. and under nitrogen, was added dropwise isobutyl chloroformate (11.5 g; 10.9 ml; 84.0 mmol). After 15 min a solution of (3β,5β,7α,12α)-3-amino-7,12-dihydroxy-cholan-24-oic acid methyl ester (prepared according to Example 5) (29.5 g; 70.0 mmol) in THF (100 ml) was added dropwise to the reaction mixture at 0° C. After 20 min the reaction mixture was allowed to rise to room temperature and stirred overnight. The suspension was filtered through a sintered funnel and the filtrate was evaporated under reduced pressure to give a residue that was dissolved in Et2O and washed with a saturated aqueous solution of NaHCO3 and H2O. The organic phase was separated, dried and then evaporated under reduced pressure. The solid residue was purified by flash chromatography to give the desired product as a white solid (25.3 g; 43.7 mmol).
