Bakers' yeast reduction of thiophenepropaenals. Enantioselective synthesis of (S)-2-methyl-1-alkanols via bakers' yeast mediated reduction of 2-methyl-3-(2-thiophene)propenals
Palladium-Catalyzed β Arylation of Carboxylic Esters
作者:Alice Renaudat、Ludivine Jean-Gérard、Rodolphe Jazzar、Christos E. Kefalidis、Eric Clot、Olivier Baudoin
DOI:10.1002/anie.201003544
日期:——
Alter ego: In the presence of an appropriate palladium(0) catalyst, carboxylicesters underwent β arylation instead of the more common α‐arylation reaction with aryl halides containing an ortho electronegative substituent (see scheme; Cy=cyclohexyl). An asymmetric version of the reaction gave the product with an enantiomeric ratio of up to 77:23.
Highly enantioselective hydrogenation of a variety of 2-substituted-2-alkenols has been achieved using a ChenPhosâRh complex as catalyst, giving â¥99% ee for most substrates. Optically active antifungal agent amorolfine was first synthesised using hydrogenation as the key step.
A biocatalytic approach to nonracemic 2-methyl-3-(2-thiophene)-1-propanols as chiral building blocks for the synthesis of pyridine alkaloids
作者:Franz Bracher、Thomas Papke
DOI:10.1016/0957-4166(94)80073-1
日期:1994.9
(S)-2-Methyl-3-(2-thiophene)-1-propanol was prepared by an improved baker'syeast-mediated asymmetric reduction of the corresponding 2,3-unsaturated aldehyde. (R)-2-Methyl-3(2-thiophene)-1-propanol was obtained by enzymatic kinetic resolution of the racemic alcohol in an organic solvent. Both enantiomers are versatile chiral building blocks for the synthesis of 3-alkyl pyridine alkaloids.
Enantioselective transesterifications of 2-methyl-1-alcohols catalysed by lipases from Pseudomonas
作者:On Nordin、Erik Hedenström、Hans-Erik Högberg
DOI:10.1016/s0957-4166(00)86227-8
日期:1994.5
Racemic beta-methyl-2-thiophenepropanol was resolved (E approximate to 200) via transesterification catalysed by lipase from Pseudomonas fluorescens using an excess of vinyl acetate in chloroform at an initial water activity: a(W) = 0.32. When trying to resolve rac-2-methyl-1-alkanols more modest E-values were obtained (E approximate to 10) and were of the same order of magnitude irrespective of substrate chainlength, water activity, immobilization, acyl donor or other Pseudomonas derived lipases. However, the reaction rates are affected by variations of these parameters. Both the rates and E-values were influenced by the nature of the solvent.