Equilibria in vitamin D3. Preparation and properties of 6-methylvitamin D3 and its isomers

6-Methylvitamin D3 and its isomers, the corresponding previtamin, trans-vitamin, and tachysterol were prepared from 6-oxo-3,5-cyclovitamin D3; their relative thermodynamic stabilities were established, and compared with the stabilities of the respective vitamin D3 isomers.