Reactions of vitamin E and its model compound 2,2,5,7,8-pentamethylchroman-6-ol with ozone

Reaction of vitamin E [(R,R,R)-alpha-tocopherol] with ozone in acetonitrile yielded alpha-tocopheryl quinone and its precursor 8a-hydroxytocopherone, which accounted for approximately 30% of the products at < 50% alpha-tocopherol oxidation. In addition, two novel products were identified as epimers of 10-acetyl-7-(4',8',12'-trimethyltridecyl)-3,4,7-trimethyl-2-oxo- 1,6-dioxaspiro[4.5]-deca-3,9-diene. These spiro products were formed in equal amounts in a combined yield of approximately 33% after complete alpha-tocopherol oxidation. Ozonation of the vitamin E model compound 2,2,5,7,8-pentamethylchroman-6-ol yielded an analogous spiro product, 10-acetyl-3,4,7,7-tetramethyl-2-oxo-1,6-dioxaspiro[4.5]deca-3,9-di ene, whose structure was confirmed by X-ray crystallography. The spiro products may be formed by ozone addition to the chroman ring and subsequent rearrangement to ring-opened hydroxyacid products, which yield spiro products by ring closure due to dehydration. Novel spiro products formed by ozonation of vitamin E may be unique markers of ozone interaction with lipid structures that contain vitamin E.