Lepadiformine A、B 和 C 是使用还原环化策略以对映体纯形式合成的。N -Boc α-氨基腈被去质子化并用对映体纯二溴化物烷基化以提供第一个环。操纵产物以引入磷酸盐离去基团,随后的还原锂化和分子内烷基化形成具有高立体选择性的第二个环。第三个环是通过去保护的胺分子内置换甲磺酸盐形成的。Lepadiformine A 和 B 含有一个与胺相邻的羟甲基。使用 Polonovski-Potier 反应作为关键步骤,按顺序引入该附属物。合成策略具有立体选择性和收敛性,并证明了N的效用-Boc α-氨基腈作为生物碱合成的关键。
Reactions between acyclic (E)-allylic acetates and arylboronic acids in the presence of a palladium catalyst prepared from Pd(OAc)(2), phenanthroline (or bipyridine), and AgSbF(6) (1:1.2:1) proceeded with excellent gamma-selectivity to afford allyl-aryl coupling products with E-configuration. The reactions of alpha-chiral allylic acetates took place with excellent alpha-to-gamma chirality transfer
Asymmetric Synthesis and Sensory Evaluation of Sedanenolide
作者:Daichi OGURO、Hidenori WATANABE
DOI:10.1271/bbb.110206
日期:2011.8.23
The synthesis and sensory evaluation of enantiomeric sets of sedanenolide (1) and 3-butylphthalide (3) are described. The asymmetric synthesis was achieved via the intramolecular Diels-Alder reaction of chiral propargylester (5) which was prepared from opticallyactive propargyl alcohol (4) and 2,4-pentadienoic acid. The sensory evaluation of these enantiomers revealed that there were distinct differences
Mutation of Cysteine-295 to Alanine in Secondary Alcohol Dehydrogenase from Thermoanaerobacter ethanolicus Affects the Enantioselectivity and Substrate Specificity of Ketone Reductions
作者:Christian Heiss、Maris Laivenieks、J.Gregory Zeikus、Robert S Phillips
DOI:10.1016/s0968-0896(01)00073-6
日期:2001.7
The mutation of Cys-295 to alanine in Thermoanaerobacter ethanolicus secondaryalcoholdehydrogenase (SADH) was performed to give C295A SADH, on the basis of molecular modeling studies utilizing the X-ray crystal structure coordinates of the highly homologous T. brockii secondaryalcoholdehydrogenase (1YKF.PDB). This mutant SADH has activity for 2-propanol comparable to wild-type SADH. However, the
We have developed a copper-catalyzedsubstitutionreaction of propargylic ammonium salts with aryl Grignard reagents. The reaction is stereospecific and α-regioselective and proceeds with exceptional functional group tolerance. Conveniently, a stable, inexpensive, and commercially available copper salt is used and no added ligand is required.
Synthesis of Chiral 3-Substituted Phthalides via Rhodium(I)-catalyzed Crossed Alkyne Cyclotrimerisation
作者:Bernhard Witulski、Axel Zimmermann
DOI:10.1055/s-2002-34883
日期:——
3-Substituted phthalides were synthesized for the first time by crossed alkyne cyclotrimerisations with Wilkinson’s catalyst. Esterification of propiolic acids with chiral propargylic alcohols by either the DCC/DMAP or the Mitsunobu method allows the synthesis of either enantiomeric form of diyne esters, that are used in crossed alkyne cyclotrimerisations with acetylene to provide 3-substituted phthalides in both enantiomeric forms.