Precalciferol - Calciferol Conversion

Antarafacial sigmatropic rearrangement of the order [1, 7] has been observed in this case. This is very important reaction from biological point of view. 

Rotation around single bond in triene system 

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From a study of thermal transformations of cholecalciferol, it was concluded that, contrary to previous reports, conversion into pyro- and isopyro-cholecalciferol was measurable at temperatures as low as 110 °C. It was further established that between 100 and 160 °C the rate of formation of pyro- and isopyro-cholecalciferol is lower than that of the precalciferol to calciferol conversions. " Reaction of the 22-oxo-compound (253) with the ylide (280), derived from reaction of methylenetriphenylphosphorane in THF with isobutylene oxide at 0°C, gave the A -compound (281) (Z 15 85). The complete retention of configura-... 

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