The use of 4,4-disubstituted nopinones for natural-product synthesis. Synthesis of elemanoid sesquiterpenes
- Publikations-Art
- Zeitschriftenbeitrag
- Autoren
- Kato, M.; Watanabe, M.; Vogler, B.; Awen, B. Z.; Masuda, Y.; Tooyama, Y.; Yoshikoshi, A.
- Erscheinungsjahr
- 1991
- Veröffentlicht in
- J. Org. Chem.
- Band/Volume
- 56/25
- Seite (von - bis)
- 7071-6
A general and convenient synthetic route to 4,4-disubstituted nopinones I [R = (CH2)nCH:CH2, CH2CH2CMe:CH2; n = 0, 2, 3; R1 = H] from (+)-nopinone (II) is developed and applied to the asym. synthesis of some representative elemanoid sesquiterpenes. Phenylsulfenylation of I provided the 3-phenylthio deriv. (III) in high yield. A convenient transformation of III to I (R1 = SO2Ph), was accomplished via 3-ClC6H4CO2OH oxidn. followed by Pummerer rearrangement and conjugate addn. of C nucleophiles to the resulting enones. Reductive desulfurization of I (R1 = SO2Ph) provided I (R1= H) in good overall yield from II. .beta.-Elemenone and eleman-8.beta.,12-olide were prepd. in optically active form from (1R,4S,5S)-I (R = vinyl, R1 = H)