Studies of the antenna effect in polymer molecules. 24. Solar photosynthesis of previtamin D3 in aqueous solutions of poly(sodium styrenesulfonate-co-2-vinylnaphthalene)

Article abstract of DOI:10.1021/ja00067a012

The photochemical step in the synthesis of vitamin D₃ in an aqueous solution of poly(sodium styrenesulfonate-co-2-vinylnaphthalene) (PSSS-VN) was studied using solar light. The photoisomerization of 7-dehydrocholesterol to previtamin D₃ was found to be exceptionally clean and efficient. The process was shown to be photosensitized by the pendant naphthalene chromophores in the copolymer via singlet-singlet energy transfer. The lack of tachysterol, a major side product formed during photoisomerization in organic solution, was explained by triplet-sensitized isomerization of tachysterol to previtamin. Triplet-triplet energy transfer from excited polymeric naphthalene chromophores to tachysterol is efficient because of the high local concentration of tachysterol in the vicinity of the energy donors.