Studies on vitamin D (calciferol) and its analogs. 23. Effect of 3-methyl substituents on the thermal [1,5]- and [1,7]-sigmatropic hydrogen shifts of vinylallenes and other seco steroids related to vitamin D: synthesis of 3-methyl- and 3,3-dimethyl-substituted analogs of 3-deoxy-1.alpha.,25-dihydroxyvitamin D3
Vitamin D (calciferol) and its analogs. 20. Synthesis of 3-deoxy-3,3-dimethyl-1-hydroxyvitamin D3 from vinylallene intermediates and related thermal and configurational studies