The use of 4,4-disubstituted nopinones for natural-product synthesis. Synthesis of elemanoid sesquiterpenes
摘要:
A general and convenient synthetic route to 4,4-disubstituted nopinones 14 from (+)-nopinone (1) is developed and applied to the asymmetric synthesis of some representative elemanoid sesquiterpenes. Phenylsulfenylation of 1 provided sulfide 6 in high yield. A convenient transformation of 6 to 3-(phenylsulfonyl)-4,4-disubstituted-nopinones 13 was accomplished by (i) m-CPBA oxidation of a sulfide compound followed by the Pummerer rearrangement and (ii) the conjugate addition of carbon nucleophiles to the resulting enones, 6 --> 8 --> 9 and 9 --> 10,11 --> 13. Subsequent reductive desulfurization of the adducts 13 provided 14 in good overall yield from 1. Bicyclic ketones 14 are envisioned as promising intermediates for natural product synthesis. As examples, syntheses of two elemanoid sesquiterpenes, beta-elemenone (16) and eleman-8-beta,12-olide (17) in optically active form from (1R,4S,5S)-4,6,6-trimethyl-4-vinylbicyclo[3.1.1]heptan-2-one (14a) were carried out.
Stereoselective first total synthesis of (4S)-trans-β-elemenone was achieved from (S)-2-cyclohexen-1-ol, prepared easily by the asymmetric reduction of 2-cyclohexen-1-one with chiral hydride reagent.
Carbocyclic construction by the [2,3]sigmatropic rearrangement of cyclic sulfonium ylides. a new entry for the stereoselective synthesis of substituted cyclohexanones
作者:Fusao Kido、Kazuo Yamaji、Subhash C. Sinha、Toshiya Abiko、Michiharu Kato
DOI:10.1016/0040-4020(95)00409-2
日期:1995.7
The rhodium(II)-catalyzed cyclization of acyclic α-diazo-β-keto esters 1c,d provided stereoselectively the highlysubstituted cyclohexanones 3c,d respectively, by the [2,3]sigmatropic rearrangement via stereocontrolled nine-membered allylsulfonium ylides 2c,d. Further elaboration of 3d toward the cyclohexanone 36 accomplished asymmetric formal syntheses of the representative elemanoids, 37 and 38.
Efficient synthesis of the anticancer β-elemene and other bioactive elemanes from sustainable germacrone
作者:Alejandro F. Barrero、M. Mar Herrador、José F. Quílez del Moral、Pilar Arteaga、Niklas Meine、M. Carmen Pérez-Morales、Julieta V. Catalán
DOI:10.1039/c0ob00467g
日期:——
Highly efficient preparations of anticancer β-elemene and other bioactive elemanes were carried out using the natural product germacrone as a renewable starting material. The syntheses were achieved in only 3â5 steps with excellent overall yields (43â54%). An enantioselective approach to these molecules is also described
oxygen functionalities is principally possible by modification of the basic concept. Methods for the oxidative generation of terpenoid exo-methylene lactone and furan units are exemplified by synthesis of menthofuran and the -menthenolides from isopulegols.