Synthesis of new 18-substituted analogues of calcitriol using a photochemical remote functionalization.

Cornella, I.; Pérez Sestelo, J.; Mouriño, A.; Sarandeses, L. A.


J. Org. Chem. 2002, 67, 4707–4714 (DOI: 10.1021/jo020022z).

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A novel convergent synthetic approach to new analogues of calcitriol modified at the C-18 position is reported. The key step in the synthesis is the 20-hydroxyl-directed photochemical iodination of the 18-methyl group in the presence of (diacetoxyiodo)benzene. Using this methodology, two new analogues of calcitriol were prepared: the first contains a hydroxylated alkyl side chain attached at C-18 with the natural side chain replaced by an isopropylidene group; the second is a conformationally locked analogue due to an extra oxacycle between the C-18 and C-20 positions.