Enantiospecific Syntheses of (+)-Crotepoxide, (+)-Boesenoxide, (+)-β-Senepoxide, (+)-Pipoxide Acetate, (−)-iso-Crotepoxide, (−)-Senepoxide, and (−)-Tingtanoxide from (−)-Quinic Acid1

A convenient strategy that is ideally suited for the construction of all the naturally occurring cyclohexane diepoxides and cyclohexene epoxides is described. The key intermediate 12, a 1,3-cyclohexadiene, has been prepared from (−)-quinic acid in 11 steps with 18% overall yield. Singlet oxygen photooxygenation of the 1,3-cyclohexadiene followed by rearrangement of the resultant endoperoxides with either cobalt- meso -tetraphenylporphyrin or trimethyl phosphite afforded enantiopure (+)-crotepoxide, (+)-boesenoxide, and (−)- iso -crotepoxide or (−)-senepoxide, (+)-β-senepoxide, (+)-pipoxide acetate, and (−)-tingtanoxide, respectively.