Catalytic Asymmetric Synthesis of Allylic Aryl Ethers
摘要:
The reaction of trichloroacetimidate derivatives of (Z)-2-alken-1-ols with phenol nucleophiles in the presence of the palladium(II) catalyst [COP-OAc](2) provides 3-aryloxy-1-alkenes in high yields and high enantiomeric purity (typically 63-90% yield and 90-97% ee). The reaction is exemplified by 20 examples. The method employs 1 mol % of the commercially available catalysts (S)- or (R)-[COPOAc](2), produces the branched isomer with unprecedented regioselectivity, and is compatible with the presence of base-labile functionality in either reactant.
The substratespectrum of the inverting alkylsulfatase Pisa1 was investigated using a range of sec‐alkyl sulfate esters bearing aromatic, olefinic and acetylenic moieties. Perfect enantioselectivities were obtained for substrates bearing groups of different size adjacent to the sulfate ester moiety. Insufficient selectivities could be doubled by using dimethyl sulfoxide (DMSO) as co‐solvent. Hydrolytically
Rearrangements and Stereomutations of Metallacycles Derived from Allenes and Imidozirconium Complexes
作者:Forrest E. Michael、Andrew P. Duncan、Zachary K. Sweeney、Robert G. Bergman
DOI:10.1021/ja045607k
日期:2005.2.1
azametallacyclobutenes generated via [2+2] cycloaddition of allenes and imidozirconium complexes have been studied. Metallacycles derivedfromallenes bearing beta-hydrogen atoms racemize at room temperature by reversible beta-hydride elimination, a process which is also responsible for their eventual conversion to monoazadiene complexes. Metallacycles derivedfrom diarylallenes racemize by reversible thermal bond
Synthesis of optically active alkynyl alcohols and α-hydroxy esters by microbial asymmetric hydrolysis of the corresponding acetates
作者:Kenji Mori、Hiroko Akao
DOI:10.1016/0040-4020(80)85030-7
日期:1980.1
Asymmetric hydrolysis of the acetates of racemic alkynyl alcohols and α-hydroxy esters by Bacillus subtilis var. Niger afforded optically active acetates and alcohols in 7–90% optical purities. The both enantiomers of optically pure mandelie acid were prepared by this microbial method.
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
The oxidoreductases Lactobacillus brevis alcohol dehydrogenase (LBADH) and Candida parapsilosis carbonyl reductase (CPCR) are suitable catalysts for the reduction of ketones to afford enantiopure sec. alcohols. A broad variety of alkynones (1, 3, and 5) are accepted as substrates and the corresponding propargylic alcohols (2, 4, and 6) are obtained in good yield and excellent enantiomeric excess. By