Alcohols Of High Optical Purity Research Articles

Direct observation of redox reactions in Candida parapsilosis ATCC 7330 by Confocal microscopic studies

Confocal microscopic studies with the resting cells of yeast, Candida parapsilosis ATCC 7330, a reportedly versatile biocatalyst for redox enzyme mediated preparation of optically pure secondary alcohols in high optical purities [enantiomeric excess (ee) up to >99%] and yields, revealed that the yeast cells had large vacuoles under the experimental conditions studied where the redox reaction takes place. A novel fluorescence method was developed using 1-(6-methoxynaphthalen-2-yl)ethanol to track the site of biotransformation within the cells. This alcohol, itself non-fluorescent, gets oxidized to produce a fluorescent ketone, 1-(6-methoxynaphthalen-2-yl)ethanone. Kinetic studies showed that the reaction occurs spontaneously and the products get released out of the cells in less time [5 mins]. The biotransformation was validated using HPLC.

ChemInform Abstract: Chiral N,N-Dialkylnorephedrines as Catalysts of the Highly Enantioselective Addition of Dialkylzincs to Aliphatic and Aromatic Aldehydes. The Asymmetric Synthesis of Secondary Aliphatic and Aromatic Alcohols of High Optical Purity.

The chiral N,N-dialkylnorephedrine-catalyzed addition of dialkylzincs to aliphatic and aromatic aldehydes afforded secondary alcohols of high optical purity (to >95% ee). Among the N,N-di(primary alkyl) norephedrines, N,N-di-n-butylnorephedrine (DBNE, 3d) was found to be the most effective catalyst. 1-Phenyl-2-(1-pyrrolidinyl) propan-1-ol (3i) and N,N-diallylnorephedrine (3j) were also highly effective catalysts. The method described provides optically active secondary aliphatic alcohols of high optical purity which cannot be prepared by conventional methods

Primary allenic alcohols of high optical purity via lipase catalyzed resolution

The lipase from Candida rugosa lipase (CRL) was used for the preparation of optically active primary allenic alcohols with axial chirality. The biocatalytic material used was the commercial CRL (C-CRL) and propan-2-ol-treated CRL (PT-CRL). The kinetic resolution of (±)- 1 and (±)- 3a– c in water using C-CRL resulted in either the absence of or low enantiomeric ratio, whereas PT-CRL increased the E-value. Under optimized conditions (temperature and medium used) (+)- S- 3a and (−)- R- 4 were isolated in excellent yields and high optical purity (o.p.). The resolution was carried out on multigram scale in water/ n-hexane at 4 °C.

ChemInform Abstract: Chiral Synthesis via Organoboranes. Part 48. Efficient Synthesis of trans‐Fused Bicyclic and Cyclic Ketones and Secondary Alcohols in High Optical Purities via Asymmetric Cyclic Hydroboration with Isopinocampheylchloroborane Etherate.

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.

Chiral Synthesis via Organoboranes. 48. Efficient Synthesis of Trans-Fused Bicyclic and Cyclic Ketones and Secondary Alcohols in High Optical Purities via Asymmetric Cyclic Hydroboration with Isopinocampheylchloroborane Etherate

Highly stereo- and enantioselective annelation has been achieved for the synthesis of trans-fused bicyclic and cyclic ketones via the asymmetric cyclic hydroboration of suitable cyclic dienes, such as 1-allyl-1-cycloalkenes or 1-vinyl-1-cycloalkenes and appropriate acyclic 1,4-dienes, respectively, with enantiomerically pure isopinocampheylchloroborane etherate (IpcBHCl·Et2O). The IpcBHCl·Et2O (an 86−90% equilibrium mixture) was readily synthesized by the reaction of an equivalent amount of hydrochloric acid in ethyl ether (Et2O) with optically pure isopinocampheylborane (IpcBH2). The hydroboration of the terminal double bond of a representative diene with IpcBHCl·Et2O readily provided the corresponding isopinocampheylalkylchloroborane (IpcRBCl). Subsequent hydridation of the IpcRBCl with lithium aluminum hydride (LAH, 0.25 equiv) at −20 or −25 °C generated the intermediate isopinocampheylalkylborane (IpcRBH) almost instantly, which then underwent a rapid stereospecific and enantioselective intramolecular cyclic hydroboration to provide the intermediate cyclic trialkylborane. This trialkylborane, on treatment with an aldehyde, liberated the optically pure auxiliary as α-pinene (readily recovered for recycle) to provide the corresponding cyclic borinate ester. This ester reacted smoothly with α,α-dichloromethyl methyl ether (DCME) in the presence of a hindered base (the DCME reaction) to yield, after oxidation with buffered hydrogen peroxide, the trans-fused bicyclic or cyclic ketone in high enantiomeric excess (ee). In another improved approach, in situ generated IpcBHCl·Et2O, from the reduction of isopinocampheyldichloroborane (IpcBCl2) with trimethylsilane (Me3SiH), in the presence of representative dienes in Et2O provided considerably improved optical yields of the bicyclic and cyclic ketones. The trialkylboranes obtained from suitable acyclic dienes can be easily protonolyzed to provide the secondary alcohols in high ee.

Stereochemically matched sulfinylacetates for double diastereoselection in the spac reaction

4-Chlorophenylsulfinylacetates of defined stereochemistry at sulfur were prepared from monochiral alcohols: compound 2 from (+)-menthol; 3 and 4 from (−)-8-phenylmenthol; 5 and 6 from (+)- trans-2-phenylcyclohexanol; and, 7 and 9 from (-)-10-dicyclohexylsulfamoyl-D-isoborneol. Reagents for which the sulfoxide asymmetry is matched with the inducing effect of the auxiliary give good diastereoselection in SPAC reactions affording γ-hydroxy-α,β-unsaturatod alcohols of high optical purity. Asymmetry at the sulfoxide has a greater effect than the auxiliaries on the stereochemical outcome of these reactions.

ChemInform Abstract: Enantioselective Formation of Functionalized 1,3‐Disubstituted Allenes: Synthesis of α‐Allenic ω‐Carbomethoxy Alcohols of High Optical Purity.

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.

Chiral N,N-dialkylnorephedrines as catalysts of the highly enantioselective addition of dialkylzincs to aliphatic and aromatic aldehydes. The asymmetric synthesis of secondary aliphatic and aromatic alcohols of high optical purity

The chiral N,N-dialkylnorephedrine-catalyzed addition of dialkylzincs to aliphatic and aromatic aldehydes afforded secondary alcohols of high optical purity (to >95% ee). Among the N,N-di(primary alkyl) norephedrines, N,N-di-n-butylnorephedrine (DBNE, 3d) was found to be the most effective catalyst. 1-Phenyl-2-(1-pyrrolidinyl) propan-1-ol (3i) and N,N-diallylnorephedrine (3j) were also highly effective catalysts. The method described provides optically active secondary aliphatic alcohols of high optical purity which cannot be prepared by conventional methods

ChemInform Abstract: Enantioselective Addition of Organometallic Reagents to Carbonyl Compounds: Chirality Transfer, Multiplication and Amplification

Nucleophilic addition of organometallic reagents to carbonyl substrates constitutes one of the most fundamental operations in organic synthesis. Modification of the organometallic compounds by chiral, nonracemic auxiliaries offers a general opportunity to create optically active alcohols, and the catalytic version in particular provides maximum synthetic efficiency. The use of organozinc chemistry, unlike conventional organolithium or -magnesium chemistry, has realized an ideal catalytic enantioselective alkylation of aldehydes leading to a diverse array of secondary alcohols of high optical purity. A combination of dialkylzinc compounds and certain sterically constrained β-dialkylamino alcohols, such as (–)-3-exo-dimethylaminoiso- borneol [(–)-DAIB], as chiral inducers affords the best result (up to 99% ee). The alkyl transfer reaction occurs via a dinuclear Zn complex containing a chiral amino alkoxide, an aldehyde ligand, and three alkyl groups. The chiral multiplication method exhibits enormous chiral amplification: a high level of enantioselection (up to 98%) is attainable by use of DAIB in 14% ee. This unusual nonlinear effect is a result of a marked difference in chemical properties of the diastereomeric (homochiral and heterochiral) dinuclear complexes formed from the dialkylzinc and the DAIB auxiliary. This phenomenon may be the beginning of a new generation of enantioselective organic reactions.

Enantioselective Addition of Organometallic Reagents to Carbonyl Compounds: Chirality Transfer, Multiplication, and Amplification

AbstractNucleophilic addition of organometallic reagents to carbonyl substrates constitutes one of the most fundamental operations in organic synthesis. Modification of the organometallic compounds by chiral, nonracemic auxiliaries offers a general opportunity to create optically active alcohols, and the catalytic version in particular provides maximum synthetic efficiency. The use of organozinc chemistry, unlike conventional organolithium or ‐magnesium chemistry, has realized an ideal catalytic enantioselective alkylation of aldehydes leading to a diverse array of secondary alcohols of high optical purity. A combination of dialkylzinc compounds and certain sterically constrained β‐dialkylamino alcohols, such as (–)‐3‐exo‐dimethylaminoiso‐ borneol [(–)‐DAIB], as chiral inducers affords the best result (up to 99% ee). The alkyl transfer reaction occurs via a dinuclear Zn complex containing a chiral amino alkoxide, an aldehyde ligand, and three alkyl groups. The chiral multiplication method exhibits enormous chiral amplification: a high level of enantioselection (up to 98%) is attainable by use of DAIB in 14% ee. This unusual nonlinear effect is a result of a marked difference in chemical properties of the diastereomeric (homochiral and heterochiral) dinuclear complexes formed from the dialkylzinc and the DAIB auxiliary. This phenomenon may be the beginning of a new generation of enantioselective organic reactions.

ChemInform Abstract: Stereoselective Syntheses of Ephedrine and Related 2‐Amino Alcohols of High Optical Purity from Protected Cyanohydrins.

AbstractThe O‐silylated cyanohydrins (I) react with Grignard reagents (II) to give the imines (III) which are reduced with zinc boranate, forming the β‐amino alcohols (IV) with predominance of the erythro‐isomer.

Synthesis of (S)-(+)-parasorbic acid and (S)-(+)-2-tridecanol acetate: Bakers' yeast reductions of γ and δ ketosulfones

The enantioselective reduction of 4-(p-toluenesulfonyl) butane-2-one and 5-(p-toluenesulfonyl) pentane-2-one with bakers' yeast gave the corresponding (S) alcohols in high optical purities and moderately good yields. The alcohol 2a was converted to (S)(+)parasorbic acid ( 4), while 2b was used for the preparation of (S)(+)-2-tridecanol acetate ( 7), using short synthetic sequences.

The reductive transformation of decanones with immobilized cells of Nicotiana tabacum

The biotransformation of decanones with immobilized cells of Nicotiana tabacum led to the formation of their corresponding alcohols of high optical purity.

Enzymatic resolution of norbornane-type esters

Chiral norbornane-type alcohols of high optical purity were prepared via enzymatic resolution of their racemic esters using lipases from Candida cylindracea and Pseudomonas sp. This method presents a short and efficient access to a number of chiral building blocks on a molar scale for the synthesis of optically active cyclopentane systems.

ChemInform Abstract: Asymmetric Reactions. Part 61. Preparation of Secondary Alcohols of High Optical Purity.

AbstractPartially resolved enantiomers of optically active alcohols (I), obtained by enantioselective reduction of the corresponding ketones with lithium aluminium hydride in the presence of (‐)‐quinine, were converted into their crystalline 3,5‐dinitrobenzoates [from (Ia), (Ib)] or phenylcarbamates [from ([Ia), (Ic)].

Preparation of secondary alcohols of high optical purity

Partially resolved enantiomers of optically active alcohols I-V, obtained by enantioselective reduction of the corresponding ketones with lithium aluminium hydride in the presence of (-)-quinine, were converted into crystalline 3,5-dinitrobenzoates or phenylcarbamates. The esters of the nearly optically pure enantiomers were separated by crystallization from the generally more soluble esters of the racemates. Optical purity of the hydrolytically liberated alcohols was determined by 1H NMR spectroscopy in the presence of chiral shifting agents.

Asymmetric synthesis of chiral geraniol-1- [formula omitted] and related terpenic alcohols

A convenient procedure for the synthesis of deuterium labeled terpenic alcohols of high optical purity is described.

Preparative scale synthesis of (1R) [1-2H1] or [1-3H1] primary alcohols of high optical purity

Preparative scale synthesis of (1R) [1-2H1] or [1-3H1] primary alcohols of high optical purity

ChemInform Abstract: THE STEREOSPECIFIC ASYMMETRIC REDUCTION OF FUNCTIONALISED KETONES

AbstractDie Ketone (I) und (III) werden durch Hefe zu den sek. Alkoholen (II) bzw. (IV) reduziert.

The stereospecific asymmetric reduction of functionalised ketones

The reduction of functionalised ketones with actively fermenting yeast gives secondary alcohols of high optical purity in moderate yields; the method is of value for the synthesis of optically active α- and β- hydroxyesters.