A Study of the [1,7]-Sigmatropic shift of a 1-hydroxylated-3-desoxy previtamin D to vitamin D: observation of a modest primary deuterium kinetic isotope effect

The primary metabolic pathway leading to the active form of vitamin D, namely 1 alpha ,25-dihydroxyvitamin D sub(3), formally incorporates two classical pericyclic processes. These include the photochemical electrocyclic ring opening of 7-dehydrocholesterol to previtamin D sub(3) and then the thermal transformation (a (1,7)-sigmatropic hydrogen shift) of previtamin D sub(3) to vitamin D sub(3). In this communication the authors describe initial studies in this area through kinetic investigations of the isomerization of 3-deoxy-1-hydroxyprevitamin D sub(3) epimers, a (1,7)-sigmatropic shift model for the previtamin form of the natural hormone.