Identification of an intermediate in autoxidation of carota-1,4-die-14-al into rugosal A

In the autoxidation of (7R,10R)-carota-1,4-dien-14-al 1, which is a precursor of an antifungal compound rugosal A 2, in Rosa rugosa leaves, an intermediate possessing a 1,5-endoperox-2-hydroperoxy system 4 was isolated as a major product. The structures of compound 4 and other by-products including rugosal A 2 and rugosic acid A 3 were determined. These autoxidation products indicated the conversion pathway of compound 1 into rugosal A 2, similar to the radical reaction pathway in the autoxidation of polyunsaturated fatty acids.