165. Synthesis of (R)- and (S)-4-Methyl-6-2'-methylprop-1'-enyl-5,6-dihydro-2H-pyran (Nerol oxide) and Natural Occurrence of its Racemate

Article abstract of DOI:10.1002/hlca.19800630626

Following a know procedure, a mixture of (-)-(2S,3R)- and (+)-(2R,3R)-2,3-epoxy-citronellols (5) was prepared from (-)-(R)-linalool (3) via epoxy alcohol 4 and then reduced to (-)-(R)-3-hydroxy-citronellol (6).Sensitized photooxygenation of (-)-(R)-diol 6 led in part to (-)-(R)-triol 8 which was cyclodehydrated by dilute acid to a mixture of diastereoisomeric tetrahydropyran-4-ols 9 and 10.Dehydration of hydroxy ethers 9 and 10 afforded (-)-(S)-nerol oxide (11) and (+)-(R)-nerol oxide (12), respectively, with an optical purity of 91percent.Nerol oxide isolated from Bulgarian rose oil (0.038percent) proved to be racemic.These results shed some light on the formation of nerol oxide in plants.