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Terpenes and terpene derivatives, XXXIII. Synthesis of rac‐cis ‐ and ‐ trans ‐dracunculifoliol and their 10‐epimers

1995; Wiley; Volume: 1995; Issue: 2 Linguagem: Inglês

10.1002/jlac.199519950233

0947-3440

Peter Weyerstahl, Helga Marschall, K. SCHNEIDER,

Oxidative Organic Chemistry Reactions

Abstract The cis ‐aldehyde 9 , a key intermediate in the total synthesis of cis ‐dracunculifoliol ( 1 ) previously isolated from Vassoura oil, was prepared starting from the bicyclic enone 5 via the nitrile 8 . Grignard reaction of 9 led exclusively to epi ‐ 1 . Oxidation to the ketone 10 followed by reduction gave a separable mixture of the natural isomer 1 and epi ‐ 1 . – The synthesis of trans ‐dracunculifoliol ( 2 ) starts with the 6‐methoxytetralone 14 . After some usual steps, the trans ‐octalin 17 was obtained. MMPP‐HIO 4 oxidation gave compound 19 which was transformed into the iodo ester 26 , precursor of the hydrindane ester 27 . Analogously to the synthesis of epi ‐ 1 the epi ‐ trans ‐dracunculifoliol ( epi ‐ 2 ) was formed via alcohol 28 and aldehyde 29 . Oxidation ( 30 ) and reduction furnished the natural trans alcohol 2 . – Olfactory evaluation of the purified isomers 1 , epi ‐ 1, 2 , and epi ‐ 2 showed that all of them possess only a weak, woody odor. Therefore, the dracunculifoliols 1 and 2 are not responsible for the typical earthy, leathery, and spicy odor of the Vassoura oil.