| 摘要 |
<p>The present invention relates to a novel process for the preparation of active-type vitamin D3 compounds and their intermediates. In accordance with the present invention, a large amount of an active-type vitamin D3 compounds, for example 1 alpha -hydroxycholecalciferol, 1 alpha ,25-dihydroxycholecalciferol and the like, is efficiently prepared with high industrial advantages by a novel processes, which comprises (i) reacting hydroxycholesta-5-enes having the hydroxyl groups protected with lower alkoxycarbonyl group as a starting material with allylic brominating agent and dehydrobrominating agent to prepare the corresponding hydroxycholesta-5,7-dienes, (ii) exposing the hydroxycholesta-5,7-dienes to ultraviolet irradiation or to a combination of the irradiation with thermal isomerization to obtain a mixture of the unreacted hydroxycholesta-5,7-dienes and previtamin D3 compounds or a mixture of the unreacted hydroxycholesta-5,7-dienes and the protected active-type vitamin D3 compounds, (iii) separating the mixture into the unreacted hydroxycholesta-5,7-dienes and previtamin D3 compounds or the protected active-type vitamin D3 compounds, (iv) recycling the unreacted hydroxycholesta-5,7-dienes as reuse and (v) thermally isomerizing the remaining compounds and/or splitting off the protective groups. The process for the preparation of active-type vitamin D3 compounds, in the present invention, is of very high industrial value, capable of carrying out by simple operation and adaptable to large scale commercial production.</p> |
