The syntheses are described of previtamin D - and vitamin D analogues to be used for the study of the thermal precalciferol+ cal- ciferol isomerization reaction. A previtamin D analogue (4) prepared as indicated by Inhoffen could not be obtained in a pure state. Closer inspection revealed that the final step, the selective partial hydrogenation of the triple bond of 3, yielded a mixture of isomers. Two calciferol analogues (15A and 15s) were synthesized, following routes used ...
