Biotransformation of l‐menthol by soil‐borne plant pathogenic fungi (Rhizoctonia solani)

The biotransformation of l‐menthol was investigated by using nine isolates of Rhizoctonia solani (AG‐1‐IA Rs24, Joichi‐2, RRG97‐1; AG‐1‐IB TR22, R147, 110.4; AG‐1‐IC F‐1, F‐4 and P‐1) as a biocatalyst. In the cases of Rhizoctonia solani F‐1, F‐4 and P‐1, almost all of the substrate was consumed in 3 days and the major metabolite increased rapidly for the first of 3 days incubation. The structure of the major metabolite was elucidated on the basis of its spectral data. The major metabolite was determined to be (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol which indicated that l‐menthol was hydroxylated at the C‐6 position. From the main component analysis, the nine isolates of Rhizoctonia solani were divided into two groups based on their ability to transform l‐menthol to (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol. This is the first report on the biotransformation of l‐menthol by Rhizoctonia solani. © 2001 Society of Chemical Industry     

Biotransformation of (+)‐ and (−)‐bornyl acetate using the plant parasitic fungus Glomerella cingulata as a biocatalyst

The microbial transformations of (+)‐ and (?)‐bornyl acetate were investigated using the plant parasitic fungus, Glomerella cingulata. As a result, (+)‐ and (?)‐bornyl acetate were converted to (+)‐ and (?)‐5‐exo‐hydroxybornyl acetate, (+)‐ and (?)‐5‐oxobornyl acetate and (+)‐ and (?)‐borneol respectively. The structures of the metabolic products were determined by spectroscopic data. © 2001 Society of Chemical Industry     

Efficient separation of (R)‐(‐)‐mandelic acid biosynthesized from (R,S)‐mandelonitrile by nitrilase using ion‐exchange process

BACKGROUND: (R)‐(‐)‐Mandelic acid (R‐MA) is an important intermediate and chiral regent with broad uses. An efficient method for the separation of R‐MA from the bioreaction mixture with high yield is of great importance, thus, the main objective of this work is to investigate the recovery of R‐MA using an ion‐exchange process. RESULTS: The equilibrium isotherms for the separation of R‐MA by resin HZ202 were obtained in the pH range 5.0–9.0 and temperature range 25–35 °C. The equilibrium data are well fitted by the Langmuir isotherm. Batch kinetic experiments showed that the mobility of R‐MA^? in solution was rapid and the R‐MA^?/OH^? ion‐exchange process reached equilibrium after about 60 min. Adsorption kinetics were analyzed by a linear driving force mass‐transfer model, yielding good prediction of the kinetic behavior. In fixed bed column experiments, the breakthrough curves of R‐MA from the solution on resin HZ202 were determined at different flow rates and R‐MA was eluted with different concentrations of HCl. A favorable breakthrough curve and optimal eluant concentration were obtained. The results were used for the separation of R‐MA biosynthesized from (R,S)‐mandelonitrile with nitrilase, and separation was successfully achieved with above 90% recovery yield. CONCLUSION: Resin HZ202 presents favorable behavior for the recovery of R‐MA, in terms of capacity, kinetics, affinity, and susceptibility to regeneration. The results of this study provide an efficient method for R‐MA recovery from bioreaction mixture and could potentially be used in industry. Copyright © 2010 Society of Chemical Industry     

Biological stereoselective reduction of 2,6‐ and 3,5‐dimethylcyclohexanones by Glomerella cingulata

The microbial transformations of 2,6‐ and 3,5‐dimethylcyclohexanone were investigated using the plant pathogenic fungus, Glomerella cingulata. With this organism 2,6‐ and 3,5‐dimethylcyclohexanone gave the corresponding 2,6‐ and 3,5‐dimethylcyclohexanol. The metabolites from 2,6‐dimethylcyclohexanone indicated enantioselective reduction by specific optical rotation of the products. The enantiomeric excesses of the microbiological reduction products were determined by ¹H‐NMR spectra of (+)‐MTPA‐esters of the alcohols produced. The reduction of 2,6‐dimethylcyclohexanone was stereospecific, with the (2R,6R)‐ketone being converted to the corresponding (2R,6R)‐(−)‐2,6‐dimethylcyclohexanol; absolute configuration, 70% ee. On the other hand, 3,5‐dimethylcyclohexanone gave the (1α,3α,5α)‐3,5‐dimethylcyclohexanol (74%) and (1α,3β,5β)‐3,5‐dimethylcyclohexanol (26%). © 1999 Society of Chemical Industry     

Synthesis of polyblends from polypropylene and poly(R,S)‐β‐hydroxybutyrate,and their characterization

Blends of modified polypropylene (PP) with poly(R,S)‐β‐hydroxybutyrate (PHB) were prepared by casting polymer solutions, followed by compression molding into thin films. The modified polypropylene was obtained by oxidation with hydrogen peroxide. Oxidation of polypropylene produced new functional groups such as carbonyl and hydroxyl groups on the polymer chain, and a decrease in molecular weight and crystallinity of the polymers. Maximum crystallinity and mechanical properties of the polyblends were found with a PP/PHB ratio of 90/10 (w/w), and then decreased with increasing PHB content in the polyblends. Biodegradability of the polyblends was lower than that of bacterial and synthetic PHBs. Furthermore, an increase of PHB proportion in the polyblends resulted in highly non‐compatible polyblends. Hence only PHB and small parts of the polyblends were decomposed by microorganisms. Copyright © 2006 Society of Chemical Industry     

Biological enantioselective reduction of methylcyclohexanones by Glomerella cingulata

Biological reduction of alkylcyclohexanones by Glomerella cingulata was studied. With this organism regioisomeric 2-, 3- or 4-methylcyclohexanone gave the corresponding cis- and trans-methylcyclohexanols. The major metabolites of (±)-2- and (±)-3-methylcyclohexanone were cis-2- and cis-3-methylcyclohexanol. On the other hand, 4-methylcyclohexanone yielded mainly the trans-4-methylcyclohexanol. In addition, the metabolites from (±)-2- and (±)-3-methylcyclohexanone indicated enantioselective reduction by specific optical rotation of the products. The enantiomeric excesses of the microbiological reduction products were determined by NMR spectra of (+)-MTPA-esters of the alcohols produced. The reduction of (±)-2-methylcyclohexanone was stereospecific, with the (2R)-ketone being converted to the corresponding (+)-cis-2-methylcyclohexanol (1S-2R); absolute configuration, 92% e.e. On the other hand, the enantiomeric excess of the major metabolite of (±)-3-methylcyclohexanone was (−)-cis-3-methylcyclohexanol (1S-3R); absolute configuration, 33% e.e.     

Chemical Synthesis of the Epimeric (23R)‐ and (23S)‐Fluoro Derivatives of Bile Acids via Horner–Wadsworth–Emmons Reaction

A method for the synthesis of two (23R)‐ and (23S)‐epimeric pairs of 23‐fluoro‐3α,7α,12α‐trihydroxy‐5β‐cholan‐24‐oic acid and 23‐fluoro‐3α,7α‐dihydroxy‐5β‐cholan‐24‐oic acid is described. The key intermediates, 23,24‐dinor‐22‐aldehyde peracetates were prepared from cholic and chenodeoxycholic acids via the 24‐nor‐22‐ene, 24‐nor‐22ξ,23‐epoxy, and 23,24‐dinor‐22‐aldehyde derivatives. The Horner–Wadsworth–Emmons reaction of the 23,24‐dinor‐22‐aldehydes using triethyl 2‐fluoro‐2‐phosphonoacetate in the presence of LiCl and 1,8‐diazabicyclo[5,4,0]undec‐7‐ene (DBU), and subsequent hydrogenation of the resulting 23ξ‐fluoro‐22‐ene ethyl esters, followed by hydrolysis, gave a mixture of the epimeric (23R)‐ and (23S)‐fluorinated bile acids which were resolved efficiently by preparative RP‐HPLC. The stereochemical configuration of the fluorine atom at C‐23 in the newly synthesized compounds was confirmed directly by the X‐ray crystallographic data. The ¹H and ¹³C NMR spectral differences between the (23R)‐ and (23S)‐epimers were also discussed.     

(-)-1R,2S,5R-8-(4-溴苯)薄荷醇的合成与表征

以R-( )-长叶薄荷酮为起始原料,经1,4-加成、还原、溴代、水解等4步反应合成了标题化合物,总产率77%。其结构用1HNMR、13CNMR和IR进行了表征。     

Enzymatic enantioselective hydrolysis of acyloxyferrocenophanes using lipases and esterases

Enantioselective hydrolysis of racemic acetate or butyrates of 1-hydroxy [3](1,1′) ferrocenophane and endo-1-hydroxy [4](1,2) ferrocenophane using lipases, pig liver esterase and horse liver esterase resulted in the formation of (R)-alcohols and (S)-esters.     

Cationic copolymers of α,β‐poly‐(N‐2‐hydroxyethyl)‐DL‐aspartamide (PHEA) and α,β‐polyasparthylhydrazide (PAHy): synthesis and characterization

In the present study the derivatization of two water‐soluble synthetic polymers, α,β‐poly(N‐2‐hydroxyethyl)‐DL ‐aspartamide (PHEA) and α,β‐polyasparthylhydrazide (PAHy), with glycidyltrimethylammonium chloride (GTA) is described. This reaction permits the introduction of positive charges in the macromolecular chains of PHEA and PAHy in order to make easier the electrostatic interaction with DNA. Different parameters affect the reaction of derivatization, such as GTA concentration and reaction time. PHEA reacts partially and slowly with GTA; on the contrary the reaction of PAHy with GTA is more rapid and extensive. The derivatization of PHEA and PAHy with GTA is a convenient method to introduce positive groups in their chains and it permits the preparation of interpolyelectrolyte complexes with DNA. © 2000 Society of Chemical Industry     

Asymmetric Friedel–Crafts Alkylations of Indoles with Ethyl Glyoxylate Catalyzed by (S)‐BINOL‐Titanium(IV) Complex: Direct Access to Enantiomerically Enriched 3‐Indolyl(hydroxy)acetates

Enantioselective Friedel–Crafts alkylation reactions of a variety of indoles with ethyl glyoxylate, catalyzed by a chiral (S)‐BINOL‐Ti(IV) complex (10 mol %), are reported. The corresponding ethyl 3‐indolyl(hydroxy)acetates were formed in good yields and with high enantiomeric excess (up to 96 %). When methyl pyruvate or p‐chlorophenylglyoxal was used, the bisindole compound was obtained in excellent yield. A possible mechanism is proposed.     

Confined crystallization morphology of poly(ϵ‐caprolactone) block within poly(ϵ‐caprolactone)–poly(l‐lactide) copolymers

The confined crystallization of poly(?‐caprolactone) (PCL) block in poly(?‐caprolactone)–poly(l ‐lactide) (PCL‐PLLA) copolymers was investigated using differential scanning calorimetry, polarized optical microscopy, scanning electronic microscopy and atomic force microscopy. To study the effect of crystallization and molecular chain motion state of PLLA blocks in PCL‐PLLA copolymers on PCL crystallization morphology, high‐temperature annealing (180 °C) and low‐temperature annealing (80 °C) were applied to treat the samples. It was found that the crystallization morphology of PCL block in PCL‐PLLA copolymers is not only related to the ratio of block components, but also related to the thermal history. After annealing PCL‐PLLA copolymers at 180 °C, the molten PCL blocks are rejected from the front of PLLA crystal growth into the amorphous regions, which will lead to PCL and PLLA blocks exhibiting obvious fractionated crystallization and forming various morphologies depending on the length of PLLA segment. On the contrary, PCL blocks more easily form banded spherulites after PCL‐PLLA copolymers are annealed at 80 °C because the preexisting PLLA crystal template and the dangling amorphous PLLA chains on PCL segments more easily cause unequal stresses at opposite fold surfaces of PCL lamellae during the growth process. Also, it was found that the growth rate of banded spherulites is less than that of classical spherulites and the growth rate of banded spherulites decreases with decreasing band spacing. © 2019 Society of Chemical Industry     

Optimization and kinetic modeling of lipase catalyzed enantioselective N‐acetylation of ( ± )‐1‐phenylethylamine under microwave irradiation

BACKGROUND: Optically pure amines are used in the fine chemical industry as resolving agents, chiral auxiliaries, and chiral synthetic building blocks for pharmaceuticals as well as agrochemicals. Lipase‐catalyzed kinetic resolution of ( ± )‐1‐phenylethylamine with ethyl acetate as an acyl donor was achieved using immobilized lipase (Novozyme 435) as a biocatalyst under microwave irradiation. RESULTS: Response surface methodology was employed with a four‐factor‐three‐level Box‐Behnken design to evaluate the effect of synthesis parameters (speed of agitation, enzyme loading, temperature and acyl donor:amine molar ratio) on conversion, enantiomeric excess, enantioselectivity and initial rate. The optimum reaction conditions obtained were mole ratio of acyl donor:amine 1:1, temperature 49.86 °C, 0.03 g of catalyst loading and 345 rpm speed of agitation, giving 49.12% conversion, 78.83% enantiomeric excess and an enantioselectivity of 38.21. R‐stereopreference of lipase was analyzed in detail from the aspects of enzymatic kinetic mechanism and reaction activation energy of both enantiomers. CONCLUSION: Novozyme 435 was found to be the most active chiral catalyst for resolution of ( ± )‐1‐phenylethylamine under microwave irradiation. Statistical analysis was satisfactorily used to determine the optimum reaction conditions. It was found that lipase has R‐stereopreference and the reaction matches the Ping Pong Bi Bi mechanism with dead‐end inhibition of 1‐phenylethylamine. Copyright © 2011 Society of Chemical Industry     

Biotransformation of (−)‐bornyl acetate using submerged cultures of Collybia velutipes,Trametes hirsuta and Ganoderma applanatum

The biotransformation of (?)‐bornyl acetate by three Basidiomycetes, Collybia velutipes, Trametes hirsuta and Ganoderma applanatum was monitored for 7 days. The observed reactions were regio‐ and stereo‐selective hydroxylation, acetate hydrolysis and oxidation of alcohols to carbonyl compounds. Nine cyclic compounds, three of which (6‐exo‐hydroxybornyl acetate, 8‐hydroxy‐5‐exo‐hydroxybornyl acetate, 9‐hydroxy‐5‐exo‐hydroxybornyl acetate), not previously described, were isolated from the fermentation broth and therefore were identified. Product types and concentrations varied with strain and incubation time. The toxicity of the substrate was assessed from the variation of fungal biomass in the course of incubation. Copyright © 2005 Society of Chemical Industry     

Copolymers based on poly(butylene terephthalate) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone

A series of novel thermoplastic elastomers, based on poly(butylene terephthalate) (PBT) and polycaprolactone‐block‐polydimethylsiloxane‐block‐polycaprolactone (PCL‐PDMS‐PCL), with various mass fractions, were synthesized through melt polycondensation. In the synthesis of the poly(ester‐siloxane)s, the PCL blocks served as a compatibilizer for the non‐polar PDMS blocks and the polar comonomers dimethyl terephthalate and 1,4‐butanediol. The introduction of PCL‐PDMS‐PCL soft segments resulted in an improvement of the miscibility of the reaction mixture and therefore in higher molecular weight polymers. The content of hard PBT segments in the polymer chains was varied from 10 to 80 mass%. The degree of crystallinity of the poly(ester‐siloxane)s was determined using differential scanning calorimetry and wide‐angle X‐ray scattering. The introduction of PCL‐PDMS‐PCL soft segments into the polymer main chains reduced the crystallinity of the hard segments and altered related properties such as melting temperature and storage modulus, and also modified the surface properties. The thermal stability of the poly(ester‐siloxane)s was higher than that of the PBT homopolymer. The inclusion of the siloxane prepolymer with terminal PCL into the macromolecular chains increased the molecular weight of the copolymers, the homogeneity of the samples in terms of composition and structure and the thermal stability. It also resulted in mechanical properties which could be tailored. Copyright © 2010 Society of Chemical Industry     

Optical resolution of (R,S)‐2‐phenyl‐1‐propanol through enantioselective ethycellulose membranes

Enantioselective membrane was prepared using ethyl cellulose (EC) as membrane material. The flux and permselective properties of membrane using aqueous solution of (R,S)‐2‐phenyl‐1‐propanol as feed solution was studied. The employed membrane process was a pressure driven process. All kinds of important conditions including preparation and operation of membranes were investigated in this experimentation. When the membrane was prepared with 18 wt % EC, 20 wt % N,N‐dimethylformamide in casting solution, 13 min evaporation time and 0°C temperature of water bath for the gelation of the membrane, and the operating pressure and feed solution of (R,S)‐2‐phenyl‐1‐propanol were 0.2 MPa and 1.5 mg/mL, respectively, over 90% of enantiomeric excess (e.e.) and 44.2 (mg/m² h) of flux were obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Atactic poly(methyl methacrylate) blended with poly(3‐D(−)hydroxybutyrate): Miscibility and mechanical properties

Atactic poly(methylmethacrylate), aPMMA, was blended with poly(3‐D(−)hydroxybutyrate), PHB, up to a maximum composition of 25% of polyester, at 190°C in a Brabender‐like apparatus. The resulting blends quenched from the melt to room temperature were completely amorphous, and exhibited a single glass transition using DSC and DMTA, indicating miscibility of the components for this time–temperature history. Tensile experiments showed that at room temperature the 10/90 and 20/80 PHB/aPMMA blends exhibited higher values of strain at break, and slight decreases of the modulus and stress at break compared to neat aPMMA. The tensile energy at break was almost twice that of neat aPMMA. Tensile tests were also performed at 80°C, at which point the 25/75 and 20/80 PHB/aPMMA blends are above T_g, while the 10/90 and neat aPMMA are below T_g. The stress–strain curves obtained were functions of the physical state of the amorphous phase, and also depended on the difference between the test temperatures and T_g. In particular, comparing the neat aPMMA and the blends, decreases of the modulus and stress at break and a respectable increase in the strain at break were observed in the latter. Finally, the results were commented considering the thermal degradation of PHB in the melt during the blend preparation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 746–753, 2000     

Photocatalytic degradation of 2,2‐bis(4‐hydroxy‐3‐methylphenyl) propane (BPP) based on molecular recognition interaction

BACKGROUND: Endocrine disruptors in the aquatic environment and their potential adverse effects are currently issues of concern. One of these endocrine disruptors is 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane (BPP). In this work the molecular recognition interaction of BPP with β‐cyclodextrin (β‐CD) was studied using IR spectroscopy and steady state fluorescence spectroscopy, and the photocatalytic degradation behaviour of BPP based on molecular recognition interaction was investigated in a TiO₂/UV–visible (λ_max = 365 nm) system. This might provide a new method for the treatment of some organic pollutants in wastewater. RESULTS: β‐CD reacts with BPP to form a 1:1 inclusion complex, the formation constant of which is 4.94 × 10³ L mol^?1. The photodegradation rate constant of BPP after molecular recognition by β‐CD showed a 1.42‐fold increase in the TiO₂/UV–visible (λ_max = 365 nm) system. The photodegradation of BPP depended on the concentration of β‐CD, the pH value, the gaseous medium and the initial concentration of BPP. The photodegradation efficiency of BPP with molecular recognition was higher than that without molecular recognition. After 100 min of irradiation the mineralisation efficiency of BPP after molecular recognition by β‐CD reached 94.8%, whereas the mineralisation efficiency of BPP before molecular recognition by β‐CD was only 40.6%. CONCLUSION: The photocatalytic degradation of BPP after molecular recognition by β‐CD can be enhanced in the TiO₂/UV‐visible (λ_max = 365 nm) system. This enhancement is dependent on the enhancement of the adsorption of BPP, the moderate inclusion depth of BPP in the β‐CD cavity and the increase in the frontier electron density of BPP after molecular recognition. Copyright © 2008 Society of Chemical Industry     

Approaches to the Preparation of Enantiomerically Pure (2R,2′R)‐(+)‐threo‐Methylphenidate Hydrochloride

Various approaches to the preparation of enantiomerically pure (2R,2′R)‐(+)‐threo‐methylphenidate hydrochloride ( 1 ) are reviewed. These approaches include synthesis using enantiomerically pure precursors obtained by resolution, classical and enzyme‐based resolution approaches, enantioselective synthesis approaches, and approaches based on enantioselective synthesis of (2S,2′R)‐erythro‐methylphenidate followed by epimerization at the 2‐position. 1 Introduction 2 Methods for the Enhancement of Enantiomeric Purity of 1 3 Approaches Using Enantiomerically Pure Precursors Obtained by Resolution 4 Classical Resolution Approaches 4.1 Resolution of Amide and Acid Derivatives 4.2 Resolution of (±)‐threo‐Methylphenidate 5 Enzyme‐Based Resolution Approaches 6 Enantioselective Synthesis Approaches 7 Approaches Based on Enantioselective Synthesis of (2S,2′R)‐erythro‐Methylphenidate and Epimerization 8 Conclusions     

Preparation of isotacticity‐rich poly(tert‐butyl vinyl ether) by the cationic polymerization of tert‐butyl vinyl ether with dimethyl[rac‐ethylenebis(indenyl)]zirconium and tri(pentafluorophenyl)borane

tert‐Butyl vinyl ether (tBVE) was polymerized with the catalyst dimethyl[rac‐ethylenebis(indenyl)] zirconium (ansa‐zirconocene) with tri(pentafluorophenyl) borane [B(C₆F₅)₃] as a cocatalyst. The effects of various polymerization conditions, such as the polymerization time, type of polymerization solvent, polymerization temperature, and catalyst concentration, on the conversion of tBVE into poly(tBVE), its molecular weight and molecular weight distribution, and its stereoregularity were investigated. The maximum conversion of tBVE into poly(tBVE) was over 90% at a polymerization temperature of ?30°C with an ansa‐zirconocene and B(C₆F₅)₃ concentration of 3.0 × 10^?7 mol/mol of tBVE, respectively. The number‐average molecular weights of poly(tBVE) ranged from approximately 14,000 to 20,000, with a lower polydispersity index (weight‐average molecular weight/number‐average molecular weight) ranging from 1.48 to 1.77, at all polymerization temperatures. The number‐average molecular weight of poly(tBVE) increased with decreases in the polymerization temperature and catalyst concentration. The mm triad sequence fraction of poly(tBVE) polymerized with ansa‐zirconocene/B(C₆F₅)₃ at ?30°C was much higher than that of poly(tBVE) polymerized with the B(C₆F₅)₃ catalyst at ?30°C, and this indicated that the ansa‐zirconocene/B(C₆F₅)₃ catalyst system affected the isospecific polymerization of tBVE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008