| 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 compound, for example, l.alpha.-hydroxycholecalciferol, 1.alpha., 25-dihydroxycholecalciferol and the like, is efficiently prepared until high industrial advantages by a novel process, which comprises (i) reacting hydroxycholesta-5-enes having the hydroxyl groups protected with lower alkoxycarbonyl groups as starting material with an allylic brominating agent and a 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 hydroxyclolesta-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, is capable of being carried out by simple operation and is adaptable to large scale commercial production.</p> |
