| 摘要 |
PROBLEM TO BE SOLVED: To obtain a vitamin D derivative by irradiating the solution of a provitamin D derivative with UV light having a specific wavelength for a photochemical reaction, thus converting the provitamin D derivative into a previtamin D derivative in high efficiency in one step, and subsequently thermally isomerizing the obtained previtamin D derivative. SOLUTION: This method for producing (C) a vitamin D derivative comprises irradiating the solution of (A) a provitamin D derivative with UV light released from the quartz rod of an UV light irradiation device for photochemical reactions to photochemically produce (B) a previtamin D derivative, and subsequently thermally isomerizing the previtamin D derivative. The UV light irradiation device for photochemical reactions has an UV light-emitting lamp, an optical system for radiating the UV light which is emitted from the lamp and has a specific wavelength (preferably 280-320 nm), and the quartz rod into which the UV light is transmitted. A compound of formula I (R1, R3 are each H or a hydroxy group; R2 is H, a hydroxy group, a 1-10C lower alkyl or the like; R is H or a 1-10C lower alkyl; X is O-CH2 or the like), a compound of formula II, and a compound of formula III are preferable as the compounds A, B and C, respectively.
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