Studies on vitamin D and related compounds. Part 21. Photosensitized reactions

The cis-trans isomerisation of tachysterol3 and previtamin D3 trimethylsilyl ethers has been brought about by triplet sensitization. The two overall quantum yields have been estimated. It was found that the photochemical electrocyclic reactions of previtamin D3 yielding 7-dehydrocholesterol and lumisterol3 go via singlet states. The irradiation mixtures were analysed by means of GLC.