Studies on vitamin D and related compounds III. Short communication on the <i>cis‐trans</i> isomerization of calciferol and the properties of <i>“trans”</i>‐vitamin D₂

Abstract

Abstract Isomerization of vitamin D 2 in apolar solvents at room temperature under the influence of small amounts of iodine in diffuse daylight yields a compound that could be isolated in the form of the crystalline phenylazobenzoate. Spectra of solutions of the free vitamin D isomer obtained upon saponification of the ester are presented. They support the view that the isomer should be considered as trans‐vitamin D 2 having structure A (fig. 3).