反应详情

3α-hydroxy-7-keto-5β-cholan-24-oic acid (KLCA; 500.0 g, 1.28 mol) was esterified using methyl alcohol (2500 mL), in the presence of acidic catalysis (sulfuric acid, 1.0 mL) and was heated up to 62° C. to 64° C. for approximately 3 hours, to yield 3α-hydroxy-7-keto-5β-cholan-24-oic acid methyl ester (1). In this reaction, the methyl alcohol acts as the methylating reagent as well as the reaction solvent. For the work-up, the pH-value was adjusted with sodium hydroxide solution (2N) to pH 7.0 to 7.5. The solution was treated with activated carbon (25 g) for approximately 30 minutes and filtered to remove the carbon solids. Alternatively, the solution was not treated with activated carbon. To precipitate the product, water (625 mL) at 10° C. to 15° C. was added over 15 minutes and seeding material was added. The reaction mixture is stirred for 1 hour at 10° C. to 15° C. Another portion of water (1875 mL) was added over about 20 to 25 minutes. The product suspension was stirred for 30 minutes at 10° C. to 15° C. The product was isolated with a centrifuge and washed with a mixture of methanol and water (1:1, 350 mL). The water content of the wet material was quantified by Karl Fischer (KF). The material was dried in a tumble dryer under vacuum at NMT 70° C. The material can also be used in the next step without drying. The yield (calculated on dried product) is 501.4 g (1.24 mol, 96.8%).