Threo Diols Research Articles

A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay.

A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.

A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay

AbstractA colorimetric indicator displacement assay (IDA) amenable to high‐throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96‐well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn‐ or anti‐addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.

ChemInform Abstract: Tandem Carbonyl Coupling-Rearrangements Promoted by the Niobium(III) Reagent. Dual Reductive and Lewis Acid Properties of NbCl3(DME).

Abstract Benzaldehyde (1a) and acetophenone (6) are shown to undergo highly stereoselective reductive couplings by NbCl3(DME). When the reaction is performed at −10°C, the threo diols can be isolated. The intermediate niobiopinacols reveal the ability of subsequent transformations, due to the Lewis acid properties of the reagent used. Starting from 1a stereospecific acetalization leads to threo-2,4,5-triphenyl-1,3-dioxolane (3a), whereas 3,3-diphenyl-2-butanone (7) is obtained from 6 in a pinacol-pinacolone type rearrangement. Alkenes may also be formed in the competing, temperature controlled deoxygenation The stereoselectivity and the easy control of NbCl3 (DME) mediated reactions make it a promising reagent for further synthetic applications.

Pattern-Based Recognition for the Rapid Determination of Identity, Concentration, and Enantiomeric Excess of Subtly Different Threo Diols

A pattern-based recognition approach for the rapid determination of the identity, concentration, and enantiomeric excess of chiral vicinal diols, specifically threo diols, has been developed. A diverse enantioselective sensor array was generated using three chiral boronic acid receptors and three pH indicators. The optical response produced by the sensor array was analyzed by two pattern-recognition algorithms: principal component analysis and artificial neural networks. Principal component analysis demonstrated good chemoselective and enantioselective separation of the analytes, and an artificial neural network was used to accurately determine the concentrations and enantiomeric excesses of five unknown samples with an average absolute error of +/-0.08 mM in concentration and 3.6% in enantiomeric excess. The speed of the analysis was enhanced by using a 96-well plate format, portending applications in high-throughput screening for asymmetric-catalyst discovery. X-ray crystallography and (11)B NMR spectroscopy was utilized to study the enantioselective nature of the boronic acid host 2.

Fluorinated Porphyrin Tweezer: A Powerful Reporter of Absolute Configuration forerythroandthreoDiols, Amino Alcohols, and Diamines

A general and sensitive nonempirical protocol to determine the absolute configurations of erythro and threo diols, amino alcohols, and diamines is reported. Binding of diols to the porphyrin tweezer system is greatly enhanced by increasing the Lewis acidity of the metalloporphyrin. Supramolecular complexes formed between the porphyrin tweezer host and chiral substrates exhibited exciton-coupled bisignate CD spectra with predictable signs based on the substituents on the chiral center. The working model suggests that the observed helicity of the porphyrin tweezer is dictated via steric differentiation experienced by the porphyrin ring bound to each chiral center. A variety of erythro and threo substrates were investigated to verify this chiroptical method. Their absolute configurations were unequivocally determined, and thus a general mnemonic is provided for the assignment of chirality.

Cytochrome P450/NADPH‐Dependent Formation of trans Epoxides from trans‐Arachidonic Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cytochrome P450/NADPH-dependent formation of trans epoxides from trans-arachidonic acids

Trans-arachidonic acids (trans-AA) are products of cis-trans isomerization of arachidonic acid by nitrogen dioxide radical (NO2), and occur in vivo, but their metabolism is unknown. We found that hepatic microsomes oxidized trans-AA via cytochrome P450/NADPH system to epoxides, which were hydrolyzed by epoxide hydrolase to diols (DiHETEs). 14,15-trans-AA produced one erythro diol and three threo diols each having one trans double bond.

Enantioconvergent transformation of racemic cis-Dialkyl substituted epoxides to (R,R) threo diols by microsomal epoxide hydrolase catalysed hydrolysis

Both enantiomers of (±)-9,10-epoxystearic acid ( 1b), cis-(±)-5,6-epoxyhexadecane ( 1c) and cis-(±)-11,12-epoxyhexadecan-1-ol ( 1d) as well as the meso cis-9,10-epoxyoctadecane ( 1a) undergo microsomal epoxide hydrolase catalyzed hydration at the (S) carbon to give the corresponding (R,R) threo diols in a >90 e.e.

Enantioconvergent transformation of racemic cis-β-alkyl substituted styrene oxides to (R,R) threo diols by microsomal epoxide hydrolase catalysed hydrolysis

Both enantiomers of cis-β-ethyl, β- n-propyl, β- n-butyl, and β- n-hexyl substituted styrene oxides undergo microsomal epoxide hydrolase catalysed hydration at the (S) carbon to give the corresponding (R,R) threo diols in a > 90% e.e. A complete kinetic resolution of the racemic epoxide is also obtained with the β-ethyl substituted substrate, but not with its higher homologues.

Regioselective Complexation of Unprotected Carbohydrates by Platinum(II): Synthesis, Structure, Complexation Equilibria, and Hydrogen-Bonding in Carbonate-Derived Bis(phosphine)platinum(II) Diolate and Alditolate Complexes

Treatment of bis(phosphine)platinum(II) carbonate complexes (LL)Pt(CO[sub 3]) (e.g., LL = 1,3-bis(diphenylphosphino)propane) with vicinal diols (i.e., HOCR[sup 1]R[sup 2]CR[sup 3]R[sup 4]OH) gives equilibrium conversion to the corresponding diolate complexes (LL)Pt(OCR[sup 1]R[sup 2]CR[sup 3]R[sup 4]O), which are readily isolated in good yield. From competition experiments, relative diol complexation constants were determined as a function of both the diol and the phosphine substituents and found to span a range of over 10[sup 4]. Corresponding triolate and alditolate complexes were similarly prepared, for which very distinct equilibrium isomeric regioselectivities are observed, favoring complexation of [gamma],[delta]-threo diols. An X-ray structure of (dppp)Pt(D-mannitolate) shows that the mannitol is bonded to the platinum as its dianion via the oxygens on C3 and C4 to form a 2,5-dioxaplatinacyclopentane chelate ring and that three different strong intramolecular hydrogen-bonding interactions are present between the hydroxyl hydrogens and the metallacycle oxygens (O-O) (av) = 2.65(2) [angstrom], forming five-, six-, and seven-membered rings. Crystal data for PtP[sub 2]O[sub 6]C[sub 33]H[sub 38]-CH[sub 2]Cl[sub 2]: P2[sub 1]2[sub 1]2[sub 1], Z = 4, T = 20 [degree]C, a = 11.225(2) [angstrom], b = 15.875(3) [angstrom], c = 19.964(4) [angstrom], R(F[sub 0]) = 0.058, R[sub w](F[sub o]) = 0.062. 78 refs., 4 figs., 6 tabs.

Tandem carbonyl coupling-rearrangements promoted by the niobium(III) reagent. Dual reductive and Lewis acid properties of NbCl 3(DME)

Benzaldehyde ( 1a) and acetophenone ( 6) are shown to undergo highly stereoselective reductive couplings by NbCl 3(DME). When the reaction is performed at −10°C, the threo diols can be isolated. The intermediate niobiopinacols reveal the ability of subsequent transformations, due to the Lewis acid properties of the reagent used. Starting from 1a stereospecific acetalization leads to threo-2,4,5-triphenyl-1,3-dioxolane ( 3a), whereas 3,3-diphenyl-2-butanone (7) is obtained from 6 in a pinacol-pinacolone type rearrangement. Alkenes may also be formed in the competing, temperature controlled deoxygenation The stereoselectivity and the easy control of NbCl 3 (DME) mediated reactions make it a promising reagent for further synthetic applications.

Relatively simple methodology for the determination of configuration of unsaturation of bacterial monounsaturated fatty acids: application to the unsaturates of Legionella spp.

Unsaturated fatty acids of known degree, position, and configuration of unsturation were esterified, and stereospecifically dihydroxylated at the double bond(s). cis-Hydroxylation was effected using Woodward's reagent (silver acetate/iodine/acetic acid), while trans-hydroxylation was effected using Fenton's reagent (hydrogen peroxide/ferrous sulfate/acetic acid). Diols derived from monounsaturated esters were recovered quantitatively, while tetraols derived from diunsaturates were lost, presumably during extensive washing. The stereospecifically dihydroxylated esters were analyzed by thin-layer chromatography on borate-impregnated silica gel plates, and by gas-liquid chromatography, on a nonpolar capillary column, as the trimethylsilyl, acetyl, n-butylboronyl, isopropylidene, and trifluoroacetyl derivatives. For each derivative, the erythro and threo diols were readily separable, and some resolution of positional isomers was observed. Thus, the cis/trans configuration, and in some instances, the position of unsaturation of the original monounsaturated fatty acid may be deduced. However, gas chromatography-mass spectrometry of appropriately derivatized diol esters is required for unambiguous determination of position of unsaturation in most cases. These reactions are simple, use readily available reagents, and require relatively little operator attention. Further, they do not require specialized apparatus, as do hydrogenation and ozonolysis, or potentially toxic chemicals, such as osmium tetroxide. This series of analyses was applied to the unsaturated non-hydroxylated fatty acids of Legionella species, which were shown to be monounsaturated and of the cis Δ9 family. Position of unsaturation was confirmed by gas chromatography-mass spectrometry.

ChemInform Abstract: Stereocontrolled Additions of Allyltri‐n‐butylstannane to α‐Hydroxyaldehyde Derivatives. A Useful Route to Monoprotected erythro or threo Diols.

AbstractAus den Hydroxy‐aldehyd‐Derivaten (I) erhält man mit Allyl‐tributylzinn (II) Gemische der Addukte (V) und (VI).

Synthesis of the enantiomeric forms of [formula omitted] and [formula omitted] 1-benzyloxy-2,3-epoxy butane and of (3 [formula omitted],4 [formula omitted]) 4-methyl-3-heptanol

The C 4 erythro and threo diols (7) and (8) are converted either into the chiral epoxides (13) and (15) or into the enantiomers (14) and (16); the epoxide (13) is used as chiral synthon for the preparation of (3 S ,4 S ) 4-methyl-3-heptanol (21).

Regioselectivity in enzymatic hydration of [formula omitted]-1,2-disubstituted [ 18O]-epoxides

The hydration of cis -β-methylstyrene oxide, cis -2,3-octene oxide, and their 18O-enriched forms by epoxide hydrase of rat liver microsomes has been investigated. Both cis epoxides underwent quantitative enzymatic hydration yielding exclusively the corresponding threo diols, indicating that complete stereochemical inversion at a single oxirane carbon had occurred. Mass spectral analysis of diols formed enzymatically from the 18O enriched epoxides indicated they were formed with great regioselectivity, 89% and 85% of the 18O being located at the benzylic carbon of the styrene diol and at C-3 of the octane diol, respectively.

Diol Esters from the uropygial glands of mallee fowl and stubble quail

1. The uropygial gland wax of the mallee fowl contained mainly C 14 and C 16 acids and erythro 2,3-octa-decanediol. No threo diols are odd-numbered acids or diols were detected. A small amount of primary alcohols was present 2. Wax from the stubble quail contained C 11 C 20 acids and C 14 C 24 diols (mainly erythro isomers). 3. The data were compared with those reported for the chicken, turkey and green pheasant. The proportions of odd-numbered fatty acids and odd-numbered diols are similar within species. Some birds may have two distinct stereo-specific enzyme systems for biosynthesis of diols.

Erythro-Diols of wax from the uropygial gland of the turkey

The uropygial (preen) gland secretion of the domestic turkey resembles that of the chicken in consisting mainly of a diester wax. The esterified fatty acids are saturated; they include all members of the n-C(10)-C(20) homologous series, the C(17)-C(19) acids together accounting for 60% of the total. There are four major 2,3-n-alkanediols, C(19)-C(23), all having the erythro configuration as determined by thin-layer chromatography on boric acid-silica gel and by gas-liquid chromatography. The chicken uropygiols, by contrast, contain erythro and threo diols. It is suggested that the chicken possesses two biosynthetic enzyme systems for the diols, the turkey only one