Chiral Diols Research Articles

ChemInform Abstract: Synthesis of Optically Active α,β‐Epoxysilanes and Silylaminoalcohols.

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.

Synthesis of New Chiral Ligands and Their Group VI Metal Alkylidene Complexes

The new chelating chiral diol ligands (1S,2S)- and (1R,2R)-1,2-bis(2-hydroxy-2,2-bis(trifluoromethyl)ethyl)cyclopentane (TBEC-H2; 1) were synthesized. The dilithium alkoxide of TBEC was reacted with Mo(CHCMe2Ph)(NAr)(OTf)2dme (2; Ar = 2,6-(i-Pr)2C6H3) to give the chiral alkylidene complex Mo(CHCMe2Ph)(NAr)(TBEC) (3). The ligand also reacts with W(η2-diphenylcyclopropene)Cl2(O)[P(OMe)3]2 (4), W(CHCHCOCH2CH2CH2O)(O)Cl2[P(OMe)3] (5), and W(CHCHCPh2)(NAr)Cl2[P(OMe)3]2 (6; Ar = 2,6-(i-Pr)2C6H3) to the give stable corresponding tungsten oxo vinylalkylidene complexes and tungsten amide vinylalkylidene complexes, respectively. These group VI alkylidene complexes show excellent catalytic activity in both ring-opening metathesis polymerization and in ring-closing metathesis processes.

Catalytic enantioselective protonation of samarium enolates by a C 2-symmetric chiral diol

Relatively high enantioselectivity (up to 93% ee) has been achieved in the catalytic protonation of samarium enolates by the use of a C 2-symmetric homochiral diol as the catalyst and trityl alcohol as an achiral proton source for regeneration of the catalyst.

Cyclic chiral diols with C2 symmetry: Synthesis of (2R,3R)-dihydroxy-1,2,3,4-tetrahydronaphthalene

(2R, 3R)-dihydroxy-tetrahydronaphthalene 4 has been prepared via an efficient three-step synthesis from cis-(1R, 2S)-dihydroxy-1,2-dihydronaphthalene 1. The latter was obtained by bioconversion of naphthalene by a modified strain of Pseudomonas fluorescens. The diol 4 has been successfully tested in a conjugate asymmetric addition of lithium dibutyl cuprate to the monocrotonate 7.

ChemInform Abstract: Direct Synthesis of Chiral Acetals from Carbonyl Compounds and Chiral Diols: Sequential One‐Pot Asymmetric Silylcyanation Reaction Catalyzed by Scandium(III) Triflate.

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.

Synthesis of (1 [formula omitted],1 [formula omitted]′)-2,6-bis[1-(diphenylphosphino)ethyl]pyridine and its application in asymmetric transfer hydrogenation

A C 2 symmetric tridentate ligand, (1R, 1R′) 2,6-Bis[1-(diphenylphosphino)ethyl]pyridine, has been synthesized in enantiomerically pure form. A practical method to synthesize a variety of chiral pyridyl diols is reported. Asymmetric transfer hydrogenation is achieved using the tridentate ligand.

Stereoselective synthesis of acyclic natural products containing chiral vicinal diol

Abstract

Total Synthesis of (+)-Papuamine: An Antifungal Pentacyclic Alkaloid from a Marine Sponge, Haliclona sp.

The total synthesis of (+)-papuamine, the antipode of the C(2)-symmetric, optically active, pentacyclic diamine natural product, starting from a chiral diol is described. The diol is available via an asymmetric Diels-Alder reaction between 1,3-butadiene and di-(-)-menthyl fumarate. The key transformation in the synthesis is an intramolecular Pd(0)-catalyzed (Stille) coupling reaction to form the central 13-membered diazadiene macrocyclic ring.

Synthesis of optically active α,β-epoxysilanes and silylaminoalcohols

A number of optically active α,β-epoxysilanes and silylaminoalcohols have been prepared from the corresponding chiral diols in high enantiomeric excess.

Asymmetric allylation of aldehydes with allyltrichlorosilane via a chiral pentacoordinate silicate

Asymmetric allylation of aldehydes with allyltrichlorosilane modified by a chiral diol via a chiral pentacoordinate silicate gave optically active alcohols with up to 71% ee.

Synthesis of pure enantiomers of a new diol ligand, trans-4,5-Bis(2-hydroxyphenyl)-2,2-dimethyl-1,3-dioxolane

A new chiral diol, trans-4,5-bis(2-hydroxyphenyl)-1,3-dioxolane, was synthesized by the reductive coupling of O-benzylated salicylaldehyde with a low-valent titanium reagent followed by acetalization and deprotection. Resolution of the diol was achieved through a sequence of esterification with O-methylmandelic acid, chromatographic separation and purification, and methanolysis.

Cyclodextrin polymer encapsulated particles for supercritical fluid chromatography

Cyclodextrin polysiloxane encapsulated particles were prepared for packed capillary column supercritical fluid chromatography. Silica particles were deactivated using polymethylhydrosiloxane through a dehydrocondensation reaction, and then coated and crosslinked with a cyclodextrin-substituted polymethylsiloxane. Using a fluidized bed coating method, nonagglomerating polymer coated particles were obtained even when a high loading of cyclodextrin polymer (25% w/w) was used. The polarities and enantiomeric selectivites of the packing materials were investigated for a wide variety of chiral test solutes, including hydrocarbon, alcohol, ketone, ester, lactone, diol, acid and amine, using neat supercritical CO2 as mobile phase. The effects of temperature and pressure on polarity and enantiomeric selectivity were also investigated. © 1996 John Wiley & Sons, Inc.

Dioxomolybdenum(VI) Complexes with New Enantiomerically Pure Amino Diol Ligands.

(R)-Phenylglycinol is shown to be an efficient building block for the synthesis of chiral amino diols in pure diastereomeric form by epoxide ring-opening reactions. The reaction with rac-trans-stilbene oxide gives [HOCH(2)-(R)-PhCH]NH[(S)-PhCH-(R)-PhCHOH] [2(R)-3(R)-4(S)-HNO(2)H(2)] in 32% yield, which can be methylated at nitrogen to give enantiomerically pure [HOCH(2)-(R)-PhCH]NCH(3)[(S)-PhCH-(R)-PhCHOH] [2(R)-3(R)-4(S)-MeNO(2)H(2)]. These amino diol ligands have been used to prepare chiral dioxomolybdenyl complexes of the formula N(R)-2(R)-3(R)-4(S)-(HNO(2))MoO(2) (1) and N(R)-2(R)-3(R)-4(S)-(MeNO(2))MoO(2) (2). The absolute configuration at each stereocenter in the Mo(VI) complexes has been established by (1)H NOESY spectroscopy. The configuration determined for 1 has been confirmed by an X-ray analysis. Crystal data: orthorhombic P2(1)2(1)2(1), a =7.620(3), b = 13.589(2), c = 20.339(3) Å, Z = 4, R = 0.0336. The structure consists of a polymeric chain of N(R)-2(R)-3(R)-4(S)-(HNO(2))MoO(2) molecules connected through unsymmetrical Mo=O --> Mo bridges. Each metal center is coordinated in a distorted octahedral geometry by a cis dioxo unit and by two trans alkoxo atoms. The coordination polyhedron is completed by a nitrogen atom and by a bridging oxo oxygen atom from an adjacent molecule. Compound 2 catalyzes the oxidation of PPh(3) to OPPh(3) by DMSO through a mechanism that involves the intermediacy of a Mo(IV) species.

Syntheses of chiral amino alcohols and diols

Abstract

Asymmetric reduction and Meerwein‐Ponndorf‐Verley reaction of prochiral aromatic ketones in the presence of optically pure 1‐aryl‐2,2‐dimethylpropane‐1,3‐diols

AbstractIn THF solution, NaBH4 in the presence of (S)‐(‐)‐1‐(2‐chlorophenyl)‐2,2‐dimethylpropane‐1,3‐diol together with 2‐chlorobenzoic acid reduced propiophenone to 1‐ phenylpropan‐1‐ol in up to 40% enantiomeric excess (ee). Only 21% ee was obtained without an added acid. (R)‐(‐)‐butane‐1,3‐diol and (R)‐( + )‐1,1′‐binaphthalene‐2,2′‐diol did not form clear solutions with NaBH4 in THF and only gave a low ee. Of the organic acid additives investigated, (S)‐(–)‐4‐(2‐chlorophenyl)‐5,5‐dimethyl‐2‐hydroxy‐1,3,2‐dioxaphosphorinane 2‐oxide gave the highest ee (46%). However, with AlCl3/NaBH4/(S)‐(–)‐1‐(2‐chlorophenyl)‐2,2‐dimethylpropane‐1,3‐diol in THF the best result was obtained (ee 55%).Asymmetric Meerwein‐Ponndorf‐Verley (MPV) reductions of acetophenone by isopropanol in the presence of these chiral diols as auxiliary have also been carried out. For the case of aluminium triisopropoxide, (R)‐(–)‐1‐phenyl‐2,2‐dimethylpropane‐1,3‐diol and acetophenone(1/1/1), an ee of up to 20% for 1‐phenylethanol was obtained whereas with (R)‐(+)‐1,1′‐binaphthalene‐2,2′‐diol an ee of 32% was obtained. Lanthanide triisopropoxides, Ln(OiPr)3, have also been used. Of the various lanthanides (Ln = La, Y, Er, Tb, and Eu) the Er triisopropoxide with chiral (R)‐(–)‐1‐phenyl‐2,2‐dimethyl‐propane‐1,3‐diol gave the best result; 46% ee for 1‐phenylethanol. Lanthanide chloride diisopropoxides, LnCl(OiPr)2, were also used as catalysts; although these have high catalytic activities they unfortunately give little chiral recognition.

Studies of Chiral Modifiers on γ-Cyclodextrin-Pyrene Complexes Using Fluorescence Lifetime Measurements

This work focuses on the inclusion complexes of γ-cyclodextrin and pyrene as indicated by fluorescence lifetime analyses and the influences of chiral alcohols and diols on these complexes. The 2-butanol participates in the γ-cyclodextrin-pyrene complexation and produces a longer lifetime of complexed pyrene than the value determined for the complex in pure water. The enantiomeric 1,3-butanediol also produces a longer lifetime of complexed pyrene. However, a decrease in this lifetime is observed in the presence of racemic 1,3-butanediol. This study also involves an estimation of formation constants for γ-cyclodextrin-pyrene complexes by use of the fluorescence lifetime measurements.

Lipase-Catalyzed Resolution of Sterically Crowded 1, 2-Diols

An enzymatic method for preparation of the enantiomers of chiral diols 2a,b and their monoacetates 3a,b with 100% enantiomeric purity by using lipase-catalyzed esterification and/or hydrolysis was established. The (R)-enantiomers were more reactive in both acetylation of (+)-2a,b and hydrolysis of (+)-3a,b catalyzed by lipase OF-360 from Candida cylindracea.

Direct Synthesis of Chiral Acetals from Carbonyl Compounds and Chiral Diols: Sequential One-Pot Asymmetric Silylcyanation Reaction Catalyzed by Scandium(III) Triflate

Direct Synthesis of Chiral Acetals from Carbonyl Compounds and Chiral Diols: Sequential One-Pot Asymmetric Silylcyanation Reaction Catalyzed by Scandium(III) Triflate

Isolation of a highly enantioselective epoxide hydrolase from Rhodococcus sp. NCIMB 11216

Whole cells of Rhodococcus sp. NCIMB 11216 catalyze the asymmetric hydrolysis of racemic epoxides giving access to chiral epoxides and diols, which are important chiral building blocks for the synthesis of bioactive compounds. Employing a four-step purification procedure, the epoxide hydrolase responsible for the reaction was isolated and characterized to be a cofactor-independent, soluble monomeric protein of ~35kDa, exhibiting an isoelectric point of 4.7.

Asymmetric synthesis using C2-symmetric diols: Use of (5R,6R)-2,3-diacetoxy-5,6-diphenyl-1,4-dioxane as a chiral synthetic equivalent of 1,2-ethanediol 1,2-dicarbocation

Abstract A new route to chiral diol systems has been developed based on double nucleophilic addition to the cationic ions fixed on a 6-membered ring system using chiral hydrobenzoin as an auxiliary.