| 摘要 |
PROBLEM TO BE SOLVED: To stereoselectively obtain the subject compound useful as a raw material for vitamin D3 , etc., by reacting cyclochol-22-ene-24-aldehyde with nitromethane in the presence of a Ln binuclear catalyst, converting the nitro group into an ester group, and further subjecting the product to a reduction reaction, a methylation reaction, etc. SOLUTION: 6α-Methoxy-3α,5α-cyclochol-22-ene-24-aldehyde is reacted with nitromethane in the presence of a binuclear catalyst containing (R) or (S)- binaphthol derivative of formula II (R<1> is H, trimethylsilylethynyl, triethylsilylethynyl; Ln is lanthanum, samarium) as an asymmetric source. The hydroxyl group of the obtained new nitroaldol compound of formula III (* is asymmetric carbon) is protected. The nitro group of the protected compound is converted into a carboxyl group and subsequently esterified. The esterified product is subjected to the hydrogenation of the double bond, a methylating agent treatment and the removal of the protecting agent to obtain the objective of 24,25-dihydroxycholesterol of formula IV. |
