Stereochemical course of the Cope-Claisen rearrangement of the stereoisomeric 2-vinyl-3-isopropenylcyclohexylvinyl ethers. A system having .DELTA.GClaisen.++. .mchgt. .DELTA.GCope.++.
Divergent Enantioselective Synthesis of (−)-Galanthamine and (−)-Morphine
作者:Barry M. Trost、Weiping Tang、F. Dean Toste
DOI:10.1021/ja054449+
日期:2005.10.1
tricyclic intermediate is available in six steps from 2-bromovanillin and the monoester of methyl 6-hydroxycyclohexene-1-carboxylate. This intermediate requires only two steps to convert to (-)-galanthamine. Using a Heck vinylation, we found that the fourth ring of codeine/morphine could be formed. The final ring formation involves a novel visible light-promoted hydroamination. Thus, six steps are required
Opening of cyclopropyl ketones with SmI2. Synthesis of spirocyclic and bicyclic ketones by intramolecular trapping of an electrophile
作者:Gary A. Molander、Cristina Alonso-Alija
DOI:10.1016/s0040-4020(97)00499-7
日期:1997.6
A method for the opening of cyclopropyl ketones with samarium(II) iodide followed by the intramolecular trapping of an electrophile is described. This process leads to the obtainment of functionalized spirocyclic, bicyclic, and tricyclic ketones in moderate to good yields.
Biocatalytic access to nonracemic γ-oxo esters via stereoselective reduction using ene-reductases
作者:Nikolaus G. Turrini、Răzvan C. Cioc、Daan J. H. van der Niet、Eelco Ruijter、Romano V. A. Orru、Mélanie Hall、Kurt Faber
DOI:10.1039/c6gc02493a
日期:——
The asymmetric bioreduction of [small alpha],[small beta]-unsaturated [gamma]-keto esters usingene-reductasesfrom the OldYellowEnzymefamily proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and...
Starting from vinylpyranoses an iron-catalyzed tandem isomerization–intramolecular aldolization reaction was developed to prepare cyclohexenone derivatives bearing substituents on the double bond, and it has been applied in a short synthesis of 4-epi-gabosines A and B, from D-glucose.
Microwave-assisted regioselective olefinations of cyclic mono- and di-ketones with a stabilized phosphorus ylide
作者:Jinlong Wu、Dan Li、Huafeng Wu、Lijie Sun、Wei-Min Dai
DOI:10.1016/j.tet.2005.12.060
日期:2006.5
4-cyclohexanediones with the ylide at 190 °C for 20 min in MeCN afforded the exocyclicolefins in >94:6 isomer ratios. On the other hand, the same reactions carried out at 230 °C for 20 min in the presence of 20 mol % DBU furnished the endocyclicolefins in >83:17 isomer ratios. The base-mediated isomerization of the exocyclicolefins into the endocyclic isomers was primarily driven by thermodynamic stability of the