Enantioselective Total Synthesis of Marine Diterpenoid Clavulactone
作者:Zhen-Yu Yang、Hong-Ze Liao、Kang Sheng、Yong-Fei Chen、Zhu-Jun Yao
DOI:10.1002/anie.201201369
日期:2012.6.25
The key steps in the synthesis of clavulactone are formation of an enantiopure cyclopentane precursor by epoxide rearrangement and intramolecular carbonyl–ene reaction, construction of the 3,4‐dihydro‐2H‐pyran ring by intermolecular hetero‐Diels–Alder reaction, closure of the eleven‐membered ring, and finally generation of the lactone functionality by chemoselective allylic C(sp3)H oxidation.
Synthesis of (<i>Z</i>)-Trisubstituted Olefins by Decarboxylative Grob-Type Fragmentations: Epothilone D, Discodermolide, and Peloruside A
作者:Kathrin Prantz、Johann Mulzer
DOI:10.1002/chem.200901567
日期:2010.1.11
induced Grob‐type fragmentation as an easy access to trisubstituted olefins. In our case, β‐mesyloxy δ‐lactones with three stereogenic centers were chosen whose fragmentation underlies a high stereoelectronic control. Major challenges in the syntheses were the installation of quaternary stereocenters, achieved by enzymatic desymmetrization of meso‐diesters and by aluminium‐promoted stereoselective rearrangement
Metallophthalocyanine complex, Cr(TBPC)OTf: an efficient, recyclable Lewis acid catalyst in the regio- and stereoselective rearrangement of epoxides to aldehydes
The metallophthalocyanine complex Cr(TBPC)OTf works as a highly efficient, recyclable Lewisacidcatalyst for the regio- and stereoselective rearrangements of epoxides to aldehydes.
Mild and simple catalytic systems consisting of molybdenum(VI) dichloride dioxide [MoO2Cl2] as a catalyst and a phosphine as reductant have been developed for the stereospecificdeoxygenation of epoxides to alkenes. The reactions using 1,2‐bis(diphenylphosphino)ethane (dppe) and triphenylphosphine (PPh3) proceed with retention and inversion of stereochemistry, respectively. The mild reaction tolerates
characteristic Lewis acid catalyst in the regio- and stereoselective rearrangement of epoxides to aldehydes. This Cr(TPP)OTf-catalyzed reaction is an operationally simple and especially convenient method for synthesizing optically active beta-siloxy aldehydes from 2,3-epoxy silyl ethers which are readily available in enantiomerically enriched forms by the Sharpless epoxidation of allylic alcohols followed