| 摘要 |
<p>PURPOSE:To obtain the titled compound useful as a Ca metabolic regulating agent for warm-blooded animals in high yield industrially and advantageously, by irradiating a specific hydroxycholesta-5,7-diene with ultraviolet light, circulating and reusing the unreacted substance, and isomerizing the previtamin D3 under heating. CONSTITUTION:A hydroxycholesta-5,7-diene of formula I (R1 and R2 are lower alkoxycarbonyl; R3 and R4 are H or lower alkoxycarbonyloxy), e.g. 1alpha,3beta-diethoxycarbonyloxycholesta-5,7-diene, having hydroxyl groups protected by lower alkoxycarbonyloxy groups is irradiated with ultraviolet light up to a conversion of 10-40% to give a previtamin D3 of formula II. The unreacted substance present as a mixture is separated by using the solubility difference with an organic solvent, and circulated for reuse. The resultant previtamin D3 is isomerized by heat, and the protecting groups are removed to afford the aimed compound of formula III, e.g. 1alpha-hydroxycholecalciferol. EFFECT:The unreacted substance can be readily separated.</p> |
