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1、方法一：2和3经叶立德反应得到最终产品从Vitamin D2 合成片段31， of vitamin D2 6 经KMnO4 氧化的7： 2， 7经Mitsunobu反应得到8； 3， 8用SeO2氧化，得到9； 4， 9用TMS保护的10 5， 10经水解得到11， 6， 11用TMS保护得到12 7， 12氧化裂解后在氢化还原为13， 8， 13经过一步氧化得到3片段片段2 2的合成的合成A new enantioselective synthesis of the building block 2 was developed based upon the asymmetric Mukaiy
2、amaMichael reaction.19 Optically active thioester 14 (96% ee, Scheme 3), was treated with LDA and then with TMSCl to give ketene acetals 15. The latter were allowed to react with enone 5 in the presence of 5 mol% of TrSbCl6. When the majority of the reagents were consumed, the second Michael accepto
3、r 16 was added.20 The reaction product consisted of three diasteromers in a ratio of 85:11:4 (by HPLC). All our attempts to separate the major component, to which structure 17 was later assigned, failed. The mixture was subjected to cyclization to give 18 along with minor diastereomers. After NaBH4C
4、eCl3 reduction21 of these a,b- unsaturated ketones a crystalline material was obtained, which was recrystallized to afford allylic alcohol 19 in a 53% yield from 17. The structure of 19 was determined by X-ray analysis.11骨化三醇成品合成In contrast to Kocienskis23 procedure for executing the Julia alkylatio
5、n, the coupling of sulfone 2 and aldehyde 3 was accomplished using an excess of the sulfone. Treatment of 2, in THF, with BuLi (1.2 mol equivalent), at 20C, followed with a mixture of 3 and 3a (0.66 mol equivalents), at78C, afforded the adduct which was quenched with AcCl. The crude product 23 was t
6、hen reduced with 6% sodium amalgam in methanol in the presence24 of Na2HPO4. A mixture of silyloxy and acetoxy trienes 24 was obtained in a 25% overall yield from 3. This mixture was allowed to react with TBAF3H2O in THF and then with methanolic KOH to give the respective trihydroxy trienes as a mix
7、ture of geometric isomers25 in a ratio of 94:5:1. Themajor isomer, ent-1, was separated by preparative HPLC. Its retention time on an analytical HPLCcolumn was the same as that of natural 1a,25-dihydroxyvitaminD3 and the 1H NMR spectrum was identical tothat of the natural compound.方法二：片段2a的合成片段3的合成谢谢大家的关注以上方法并不适合实际生产应用，方法一合成步骤太多，并且原料也不便以上方法并不适合实际生产应用，方法一合成步骤太多，并且原料也不便 宜；方法二相对方法一来说能经济一些，同时也存在很大问题，合成步骤太多宜；方法二相对方法一来说能经济一些，同时也存在很大问题，合成步骤太多 且收率不高，不适于大生产。如果将两种方法糅合，取其精华去其糟粕，将会且收率不高，不适于大生产。如果将两种方法糅合，取其精华去其糟粕，将会 使生产成本下降。本人有现成的工艺方法，有需要的可以和本人交流使生产成本下降。本人有现成的工艺方法，有需要的可以和本人交流
