Resolution Of Secondary Alcohols Research Articles

Fermented solids that contain lipases produced by Rhizopus microsporus have an S-enantiopreference in the resolution of secondary alcohols

Lipases are widely used as biocatalysts in the resolution of racemates, where high chemo-, regio- and enantioselectivity are required. In this work, we produced lipases by culturing Rhizopus microsporus in solid-state fermentation. After the fermentation, the solids were dried, producing “Rhizopus microsporus fermented solids” (RMFS). The lipases in RMFS had high activity in the synthesis of ethyl oleate in n-heptane, retaining 100 % activity after 23 successive esterification cycles, each for 4 h at 40 °C. In the kinetic resolution of three aromatic secondary alcohols by transesterification with isopropenyl acetate, in n-heptane, RMFS showed preference for the (S)-enantiomers, in other words, an anti-Kazlauskas enantiopreference. The best results were a conversion of 23 % and an enantiomeric ratio (ESR, i.e. S relative to R) of 26 for resolution of (RS)-1-phenyl-1-ethanol, after 96 h at 40 °C. Since it is rare for lipases to have an (S)-enantiopreference, RMFS have the potential as low-cost biocatalysts for the resolution of racemates of secondary alcohols.

Polymer compositions on kinetic resolution of secondary alcohols using polymer-supported silyl chlorides

Modulating the polarity of the polymer backbone affects the selectivity of asymmetric silylation.

Lipase/Iron-Catalyzed Dynamic Kinetic Resolution of Secondary Alcohols

Lipase/Iron-Catalyzed Dynamic Kinetic Resolution of Secondary Alcohols

Kinetic Resolution of Secondary Alcohols by Chiral Phosphoric Acids

Kinetic Resolution of Secondary Alcohols by Chiral Phosphoric Acids

Dynamic Kinetic Resolution of a Wide Range of Secondary Alcohols: Cooperation of Dicarbonylchlorido(pentabenzylcyclopentadienyl)ruthenium and CAL‐B

AbstractThe substrate scope in the dynamic kinetic resolution ofsecondary alcohols was studied by using 31 structurallydifferent alcohols and isopropenyl acetate in the presence ofdicarbonylchlorido(pentabenzylcyclopentadienyl)rutheniumand Candida antarctica lipase B (Novozym 435, CAL‐B) in toluene. The enzyme and the ruthenium complex were shown to function in a highly compatible manner allowing the conversion of the racemic alcohols into the (R)‐acetates in practically theoretical yields and, in most cases, ee values exceeding 99 %. The results are fully comparable to those published previously by using earlier reported, state‐of‐the‐art ruthenium‐based catalysts for the alcohol racemization. A clear benefit of the dicarbonylchlorido(pentabenzylcyclopentadienyl)ruthenium system, when compared to other (cyclopentadienyl)ruthenium racemization catalysts, is its simple and cost‐efficient preparation.

ChemInform Abstract: Resolution of Secondary Alcohols by Enzyme-Catalyzed Transesterification in Alkyl Carboxylates as the Solvent.

Abstract The Porcine Pancreatic Lipase (PPL)- and Mucor Esterase-catalyzed resolution of 1-phenylethanol 5 in four different alkyl carboxylate solvents, viz. methyl acetate, propionate and butyrate and ethyl acetate, was evaluated. The beneficial influence of the addition of molecular sieves 4A to the reaction mixture is demonstrated. A Mucor Esterase-catalyzed resolution of 5 on a 0.5 mol scale is described. The kinetic resolution of a large variety of secondary alcohols ( 5 - 22b ) was investigated using both biocatalysts under the established optimal reaction conditions for substrate 5 .

ChemInform Abstract: Enantioselective Nucleophilic Catalysis with “Planar-Chiral” Heterocycles

Although Lewis bases (e.g., tertiary phosphines, tertiary amines, and pyridines) serve as nucleophilic catalysts for a wide array of reactions, there have been relatively few reports of enantioselective nucleophilic catalysts. In this Account, we describe the design and synthesis of a new family of chiral nucleophilic catalysts, specifically, planar-chiral heterocycles. These complexes provide good levels of enantiomeric excess in the addition of alcohols to ketenes, the rearrangement of O-acylated azlactones, and the kinetic resolution of secondary alcohols.

Syntheses of organocatalysts with one-handed helix and their application to the kinetic resolution of second alcohol

Peptide-based organocatalysts with a helical structure induced by a terminal l-histidine derivative were synthesized. These organocatalysts were applied to the kinetic resolution of secondary alcohol.

Resolution of secondary alcohols via Carica papaya lipase-catalyzed enantioselective acylation

The Carica papaya lipase-catalyzed acylation of benzylcarbinols with vinyl hexanoate proceeded smoothly and enantiospecifically (E > 200), affording the R-esters and leaving the S-alcohols intact. Thus, this plant lipase proved to be a promising biocatalyst for the resolution of alcohols as well as for that of carboxylic acids reported earlier.

Sustainable Processes Employing Ionic Liquids for Secondary Alcohols Separation

Secondary chiral alcohols are very attractive intermediates in organic synthesis of pharmaceutical and the fine-chemical industries. The processes employing ionic liquids to obtain enantiomers of secondary alcohols have become sustainable. Furthermore, physico-chemical properties of ionic liquids opened new possibilities to design “solvent free” processes for the resolution of racemic secondary alcohols. This review is aimed to highlight some of the most important achievements in resolution of secondary alcohols.

Enantioselective Oxidation of Secondary Alcohols Catalyzed by Soluble Chiral Polymeric [N′,N′‐Bis(salicylidene)ethane‐1,2‐diaminato(2—)]manganese(III) ([MnIII(Salen)]) Type Complexes in a Biphasic System.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A C2‐Symmetric Metallocene‐Pyrrolidinopyridine Nucleophilic Catalyst for Asymmetric Synthesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Dynamic Kinetic Resolution of Secondary Alcohols

Dynamic Kinetic Resolution of Secondary Alcohols

Ligand‐Modulated Palladium‐Catalyzed Aerobic Alcohol Oxidations

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Resolution of secondary alcohols using 2-acyl-3-phenyl- l-menthopyrazoles as enantioselective acylating agents

The chelation of AlCl 3 with N-acylpyrazoles leads to structural fixation of the acyl moiety and an acceleration in the rate of acylation of secondary alcohols. The chiral environment of the fixed acyl moiety of 2-acyl-3-phenyl- l-menthopyrazole 2 causes diastereofacial selectivity in the reaction with secondary alcohols, and thus 2 behaves as an enantioselective acylating agent. By the use of 2.4 molar equivalents of racemic 1-phenylethanol 3a, 2-acetyl-3-phenyl- l-menthopyrazole 2a afforded ( S)-1-phenylethyl acetate ( S)- 4aa enantioselectively and unreacted 3a was recovered with ( R)-configuration. Furthermore, the inverse configurational preferences were observed to give ( R)- 4aa and ( S)- 3a by the addition of strongly basic amines, which sometimes behaved as catalysts for enolate formation from 2 and AlCl 3. These dramatic changes in stereoselective preference should be useful properties of 2-acyl-3-phenyl- l-menthopyrazole 2 as an enantioselective acylating agent.

ChemInform Abstract: Kinetic Resolution of Secondary Alcohols via Chiral Pd(II)‐Complex‐Catalyzed Enantioselective Benzoylation Using CO and Organobismuth(V) Compound.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Biocatalysis in Organic Synthesis. Part 9. Highly Enantioselective Kinetic Resolution of Secondary Alcohols Catalyzed by Acylase.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Resolution of secondary alcohols by enzyme-catalyzed transesterification in alkyl carboxylates as the solvent.

The Porcine Pancreatic Lipase (PPL)- and Mucor Esterase-catalyzed resolution of 1-phenylethanol 5 in four different alkyl carboxylate solvents, viz. methyl acetate, propionate and butyrate and ethyl acetate, was evaluated. The beneficial influence of the addition of molecular sieves 4Å to the reaction mixture is demonstrated. A Mucor Esterase-catalyzed resolution of 5 on a 0.5 mol scale is described. The kinetic resolution of a large variety of secondary alcohols ( 5 - 22b) was investigated using both biocatalysts under the established optimal reaction conditions for substrate 5.

Resolution of secondary alcohols using lipase in diisopropyl ether

Resolution of secondary alcohols using lipase in diisopropyl ether