Mechanistic studies of the photochemical rearrangement of 1-oxolongipin-2-ene derivatives

Ultraviolet irradiation of (4R,5S,7S,8R,9S,10R,11R)-7,8,9-triacetyloxy-1-oxolongipin-2-ene () afforded the vulgarone A and the pingilonene derivatives as the major products, which were formed by a [1,3]-shift, together with the minor secondary photoproducts and . The phototransformation mechanism is discussed in terms of individual ultraviolet irradiation of and in combination with the monitoring reaction progress of by 1H NMR measurements. The stereostructures of the new carbocyclic skeleta were geometry optimized using density functional calculations.