A concise and convenient synthesis of DL-proto-quercitol and DL-gala-quercitol via ene reaction of singlet oxygen combined with [2 + 4] cycloaddition to cyclohexadiene

Article abstract of DOI:10.1021/jo962092+

Photooxygenation of 1,4-cyclohexadiene afforded hydroperoxy endoperoxides 3 and 4 in a ratio of 88:12. Reduction of 3 with LiAlH₄ or thiourea followed by acetylation of the hydroxyl group and KMnO₄ oxidation of the double bond gave proto-quercitol 10b. Application of the same reaction sequences to 4 resulted in the formation of gala-quercitol 14. Quercitols were easily obtained by ammonolysis of acetate derivatives in MeOH. The outcome of dihydroxylation reactions were supported by conformational analysis.