Studies on vitamin D and related compounds XXII: New reactions and products in vitamin D3 photochemistry

Abstract
From the mixtures resulting from U.V. irradiation (λ > 250 nm) of solutions of vitamin D3 in ethanol four novel products could be isolated besides suprasterols3 I and II. The NMR and other data suggest that two of the new compounds found are stereoisomeric vinylallene derivatives, whereas the two others may represent cyclobutene derivatives (Fig. 3). The six photoproducts of vitamin D3 correspond to what would be expected from a 1,3,5‐hexatriene occurring in a s‐trans‐Δ3cis‐s‐cis conformation.