Catalytic asymmetric desymmetrization of cyclic meso-1,3- and 1,4-diols by a phosphinite derivative of quinidine

Asymmetric monobenzoylation reactions of cyclic meso-1,3- and 1,4-diols were catalyzed by a phosphinite derivative of quinidine to afford the corresponding monobenzoylated diol with good yield and enantioselectivity. [reaction: see text]     

Enantioselective ring cleavage of dioxane acetals mediated by a chiral Lewis acid: application to asymmetric desymmetrization of meso-1,3-diols

[reaction: see text]. Phenylalanine-derived B-aryl-N-tosyloxazaborolidinones selectively activate one of two enantiotopic oxygen atoms in prochiral anti dioxane acetals derived from meso-1,3-diols, leading to enantioselective formation of ring-cleavage products. The reaction is utilized as a key step in asymmetric desymmetrization of meso-1,3-diols.     

Truncated Cinchona alkaloids as catalysts in enantioselective monobenzoylation of meso-1,2-diols

Readily synthesised quincorine and quincoridine derived chiral diamines efficiently catalyse the asymmetric monobenzoylation of cyclic and acyclic meso-1,2-diols.     

Study of the interaction and activation of lipase from Pseudomonas fluorescens in surfactant monolayers and precipitates

The activation of lipase from Pseudomonas fluorescens (PFL) upon its immobilization in surfactant coprecipitates (hexadecane-1,2-diol (HDD), cetyl alcohol (CetOH), N-cetylacetamide (CetAA), and cetylamine (CetNH₂)) organized in monolayers at the interface were studied by the Langmuir—Blodgett monolayer technique. Incorporation of the enzyme into surfactant monolayers at the surface pressure = 10 mN m^–1 results in an apparent increase in the area per molecule. In the series of noncharged surfactants CetOH—HDD—CetAA, this effect increases in proportion to the amount of the enzyme incorporated in the monolayer. The catalytic activity of the lipase—surfactant coprecipitates in an organic solvent as regards esterification increases in the same sequence, indicating similarity of the interaction of lipase with surfactant monolayers and coprecipitates. For = 10 mN m^–1, the CetNH₂ monolayer with liquid-expanded state incorporates the largest amount of the enzyme (PFL : CetNH₂ = 1 : 290); the CetOH monolayer, which exists in the condensed state under the same conditions, incorporates the smallest amount (PFL : CetOH = 1 : 1700). The hydrolytic activity of PFL in mixed monolayers with surfactants increases 1.5—11-fold; the esterification activity in surfactant coprecipitates, 1.6—9-fold. The lipase activation effects are explained by facilitated transport of substrates into mixed monolayers and surfactant—enzyme precipitates in aqueous and organic media, respectively.     

Increase in catalytic activity of Pseudomonas fluorescens lipase upon its coprecipitation with hexadecane-1,2-diol suspension

A simple method for the noncovalent modification of Pseudomonas fluorescens lipase resulting in an increase in its catalytic activity in aqueous and nonaqueous media was suggested.     

Asymmetric desymmetrization based on an intramolecular haloetherification: a highly effective and recyclable chiral nonracemic auxiliary, 2-exo-methyl-3-endo-phenyl-5-norbornene-2-carboxaldehyde, for meso-1,3- and meso-1,4-diols

A new chiral auxiliary, a 3-endo-phenyl norbornene aldehyde derivative, which is a crystalline, very stable, and easily handled, was developed for the desymmetrization of meso-1,3- and meso-1,4-diols. The key step of the method, an intramolecular bromoetherification, proceeded in a highly diastereoselective manner. A four-step sequence, 1) acetalization, 2) intramolecular bromoetherification followed by acid hydrolysis, 3) protection of the alcohol, and 4) retrobromoetherification, transformed the meso-diols into optically active derivatives. The 3-endo-phenyl norbornene aldehyde derivative was simultaneously reformed and could be used repeatedly. This is the first chemical example of a single auxiliary that is applicable for highly enantioselective desymmetrization of meso-1,3- and meso-1,4-diols; to the best of our knowledge, this is the best chemical method available for the desymmetrization of meso-1,4-diols.     

Practical one-pot stereospecific preparation of vicinal and 1,3-diols

A facile one-pot synthesis providing vicinal diols and 1,3-diols in >95% stereoisomeric purity from commercially available enantiopure hydroxy esters has been developed. The esters were reduced with DIBALH and alkylated in situ with 4-pentenylmagnesium bromide, which after workup generated the title diols as diastereomeric pairs. These pairs were easily separated by preparative chromatography, affording products with retained stereoisomeric purity from the starting materials. This method represents an expedient preparation of many common natural products, such as cerambycid beetle pheromones and intermediates towards bicyclic acetal bark beetle pheromones.     

Stereoselective syntheses and transformations of chiral 1,3-aminoalcohols and 1,3-diols derived from nopinone

A library of 1,3-difunctionalized pinane derivatives were synthesized and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. 1,3-Aminoalcohol 6a was prepared from (−)-nopinone 2 via stereoselective Mannich condensation and reduction of the resulting β-amino ketone 4. The key aminoalcohol 6a was transformed into primary, secondary and tertiary substituted aminoalcohols in order to study the effect of the substituent on catalytic activity. Starting from (−)-nopinone, cis- and trans-β-hydroxy esters 15 and 16 were prepared in a two-step stereoselective synthesis. Reduction of the hydroxy esters resulted in pinane-based 1,3-diols, while hydrolysis of the esters, followed by DCC-mediated amidation and subsequent reduction, led to cis- and trans-N-benzyl-1,3-aminoalcohols 8 and 23. trans-N-Benzyl-1,3-aminoalcohol 8 was also prepared by selective mono-debenzylation of 6a via a continuous-flow process in an H-Cube® system. The resulting aminoalcohols and diols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde.     

Synthesis of 2-alkylidene-cycloalkane-1,3-diols via enantioselective intramolecular carbolithiation

The lithiodestannylation and intramolecular anti-selective carbolithiation of α-lithiated ω-carbamoyloxy-1-alkynyl carbamates have been used to synthesize highly enantioenriched protected 2-alkylidene-cycloalkane-1,3-diols.     

Adhesion of Pseudomonas fluorescens on magnetic surfaces

The adhesion of Pseudomonas fluorescens (ATCC 700830) to perpendicularly polarized magnetic surfaces was recently discovered. The findings have found that the magnetic free surfaces from different magnetic polarities have different profound effects on the P. fluorescens bacterial adhesion to its surfaces. These phenomena can be explained by the surface magnetic effect, which was found to affect the surface free energy. An in situ experiment, by contrast microscopy and under static conditions, was conducted to determine the influence of magnetic surfaces, that are polarized under different external magnetizing field strengths, on bacterial adhesion. The effect of different magnetic polarities on the surface free energy has also been investigated.     

Arylpropane-1,3-diols in lignins from normal and CAD-deficient pines

Significant quantities of arylopropane-1,3-diols have been identified in lignins isolated from a CAD-deficient pine mutant; smaller amounts are also present in lignins from normal pine. They arise from dihydroconiferyl alcohol via the action of peroxidases which are responsible for the radical generation steps of lignification. The structures in the complex lignin polymers are proven using 2D and 3D NMR of isolated lignin fractions.     

Synthesis of 2-amino-1,3-diols incorporating the cyclobutane ring

The synthesis of free and protected 2-amino-1,3-diols with threoninol substructure that incorporate a conformational restriction defined by the cyclobutane ring is reported. The key step in the synthesis of these target compounds, namely cis- and trans-c₄-threoninols, is the addition of methylmagnesium bromide to a cyclobutanone derivative. The selectivity of the reaction is modulated by the solvent.     

Photolabile protection of 1,2- and 1,3-diols with salicylaldehyde derivatives

1,2- and 1,3-diols, including carbohydrates, can be readily caged as acetals of 5-methoxy- or 5-hydroxysalicylaldehydes. Irradiation of these acetals with 300 nm light results in their efficient (Phi = 0.2-0.3) cleavage, regenerating an aldehyde and a glycol in excellent chemical yield. Photoreactive 5-hydroxysalicylaldehyde acetals can be produced by mild in situ reduction of photostable p-quinone precursors.     

Conformational landscape of meso-(1,3-dithian-2-yl)porphyrins

An investigation of the conformational landscape of 1,3-dithian-2-yl bearing porphyrins and the rotational behavior of the dithianyl substituents in meso position was carried out by variable-temperature (VT) NMR spectroscopy. Additionally, theoretical results for alternative conformations and energy barriers were obtained by molecular modeling. The study revealed different NH trans tautomers with regard to the orientation of the dithianyl ligands for the free base porphyrins 1-3. Relatively ruffled porphyrin core conformations were established for the transition states of the dithianyl rotation, resulting in a lower rotational energy barrier for the nickel(II) complex 4 compared to that of the free base systems. The data obtained and the first depiction of a rotational transition state for the rotation of bulky meso-alkyl substituents illustrate the close structural interplay between meso-alkyl substituents and the macrocycle conformation in porphyrins.     

Electrical wiring of Pseudomonas putida and Pseudomonas fluorescens with osmium redox polymers

Two different flexible osmium redox polymers; poly(1-vinylimidazole)12-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)2Cl2](2+/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)3](2+/3+) (osmium redox polymer II) were investigated for their ability to efficiently "wire" Pseudomonas putida ATCC 126633 and Pseudomonas fluorescens (P. putida DSM 6521), which are well-known phenol degrading organisms, when entrapped onto cysteamine modified gold electrodes. The two Os-polymers differ in redox potential and the length of the side chains, where the Os(2+/3+)-functionalities are located. The bacterial cells were adapted to grow in the presence of phenol as the sole source of organic carbon. The performance of the redox polymers as mediators was investigated for making microbial sensors. The analytical characteristics of the microbial sensors were evaluated for determination of catechol, phenol and glucose as substrates in both batch analysis and flow analysis mode.     

A two-step, one-pot enzymatic synthesis of 2-substituted 1,3-diols

A biocatalytic cascade reaction was designed for the stereoselective synthesis of optically pure 2-alkyl-1,3-diols employing two enzymes. The cascade process consists of two consecutive steps: a stereoselective diketone reduction and a hydroxy ketone reduction. Chiral diols were formed by the addition of ketoreductases in the same vessel, in high stereoselectivity and chemical yield, without the isolation of the intermediate β-hydroxy ketones.