Crystal and molecular structure of 1a-hydroxylated analogs of vitamins D

Structures of two 1a-hydroxylated analogs of vitamins D, 1a-hydroxycholecalciferol and 1a-hydroxyergocalciferol, were solved and refined using single crystal X-ray diffraction. Crystallographic results are verified by 13C CP/MAS NMR. This method provided also information on molecular mobility of analogs. In the crystal state, both molecules adopt exclusively a chair b-conformation of the 6-member ring A. It has been suggested that this conformation is preferred, when vitamin D molecules participate in hydrogen bonding. This is consistent with the earlier hypothesis that the b-conformers are involved in the interaction of vitamins D with their receptors. q 2004 Elsevier B.V. All rights reserved