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     

A Zinc(II) Catalyst System for the Conia‐Ene Reaction of Alkynyl‐Aminomalonates Applicable to 5‐Endo‐Dig Reactions

The zinc(II)‐catalyzed 5‐exo‐dig (Conia‐ene) and 5‐endo‐dig cyclizations of a range of alkynyl‐α‐aminomalonates give rise to nitrogen heterocycles with good efficiency. The reaction allows the synthesis of a broad range of synthetically useful building blocks.     

Tandem Gold‐Catalyzed Hydrosilyloxylation–Aldol and –Mannich Reaction with Alkynylaryloxysilanols in 6‐exo Mode

The tandem gold‐catalyzed hydrosilyloxylation–aldol and hydrosilyloxylation–Mannich reactions were developed through the formation of an enol silyl ether catalytically generated in situ from alkynylaryloxysilanols in the 6‐exo mode in one reaction vessel.     

Copper(I)‐Catalysed Multicomponent Reaction: Straightforward Access to 5‐Hydroxy‐1H‐pyrrol‐2(5H)‐ones

A copper‐catalysed multicomponent coupling reaction between readily available (Z)‐3‐iodoacrylic acids, terminal alkynes, and primary amines was developed to smoothly access a small library of 5‐hydroxy‐1H‐pyrrol‐2(5H)‐ones in good yields. This practical and general process was applied to a short‐steps synthesis of the natural product pulchellalactam.

     

Synthesis and biological activity of medium range molecular weight polymers containing exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid

A new monomer, exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid (ETCA), was prepared by reaction of maleimidocaproic acid and furan. The homopolymer of ETCA and its copolymers with acrylic acid (AA) or with vinyl acetate (VAc) were obtained by photopolymerizations using 2,2‐dimethoxy‐2‐phenylacetophenone as an initiator at 25 °C. The synthesized ETCA and its polymers were identified by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The apparent average molecular weights and polydispersity indices determined by gel permeation chromatography (GPC) were as follows: M_n = 9600 g mol^?1, M_w = 9800 g mol^?1, M_w/M_n = 1.1 for poly(ETCA); M_n = 14 300 g mol^?1, M_w = 16 200 g mol^?1, M_w/M_n = 1.2 for poly(ETCA‐co‐AA); M_n = 17 900 g mol^?1, M_w = 18 300 g mol^?1, M_w/M_n = 1.1 for poly(ETCA‐co‐VAc). The in vitro cytotoxicity of the synthesized compounds against mouse mammary carcinoma and human histiocytic lymphoma cancer cell lines decreased in the following order: 5‐fluorouracil (5‐FU) ≥ ETCA > polymers. The in vivo antitumour activity of the polymers against Balb/C mice bearing sarcoma 180 tumour cells was greater than that of 5‐FU at all doses tested. © 2001 Society of Chemical Industry     

Novel lipase isolated from a Pseudomonas strain and its application in the synthesis of S(+)‐2‐O‐benzylglycerol‐1‐acetate

Isolation of a novel microbial lipase (EC 3.1.1.3) having specific catalytic activity for the synthesis of optically pure 2‐O‐benzylglycerol‐1‐acetate, the building block for the preparation of many β‐blockers, phospholipase A2 inhibitors and other biologically active compounds was the aim of this investigation. A Pseudomonas (strain G6), recently isolated from soil, produced an extracellular lipase. SDS–PAGE analysis showed that the lipase protein was a hexamer. The molecular weight of the sub‐units of the lipase protein were 10, 19, 29, 30, 47 and 53. The catalytic activity of the lipase was exploited for the synthesis of 2‐O‐benzylglycerol‐1‐acetate from 2‐O‐benzylglycerol through transesterification using vinyl acetate as acylating agent. High selectivity of the lipase towards the monoacetate product was demonstrated. A 97% enantiomeric excess (ee) of S(+)‐2‐O‐benzylglycerol‐1‐acetate was obtained when the reaction was carried out at room temperature with shaking. The lipase was highly active in anhydrous organic microenvironments and in non‐polar organic solvents with log P values above 2.5. © 2002 Society of Chemical Industry     

Aryl λ3‐Iodane‐Mediated 6‐exo‐trig Cyclization to Synthesize Highly Substituted Chiral Morpholines

A mild and efficient transition metal‐free approach has been developed for the synthesis of highly substituted chiral morpholines from alkenols by amino acid‐derived iodine(III) reagents via a 6‐exo‐trig cyclization. The key features of this work include the formation of three chiral centers with a high diastereomeric ratio, broad functional group compatibility, and atom/time economic methodology.

     

Facile Synthesis of Enantiopure 4‐Substituted 2‐Hydroxy‐4‐ butyrolactones using a Robust Fusarium Lactonase

A facile chemo‐enzymatic process has been developed for producing stereoisomers of 4‐substituted 2‐hydroxy‐4‐butyrolactones with good to excellent enantioselectivity. This process involves an easy separation of the diastereoisomers by column chromatography and efficient enzymatic resolution by whole cells of Escherichia coli JM109 expressing Fusarium proliferatum lactonase gene. This biocatalyst shows strong tolerance towards different substrate structures and at least three out four possible isomers could be obtained in excellent enantiomeric purity. Different substrate concentrations (10 mM–200 mM) were examined, giving a substrate to catalyst ratio of up to 26:1. This general and efficient enzymatic process provides access to stereoisomers of 4‐substituted 2‐hydroxy‐4‐butyrolactones readily and cost‐effectively. The stereochemical assignments were conducted systematically based on NMR, X‐ray diffraction and circular dichroism, leading to further understanding of the enzyme’s stereoselectivity.     

A New Class of Enantioselective Catalytic 2‐Pyrone Diels–Alder Cycloadditions

A highly enantioselective catalytic Diels–Alder (DA) cycloaddition of 2H‐pyran‐2,5‐diones (synthon of 5‐hydroxy‐2‐pyrones) has been developed with a Cinchona‐derived thiourea as the catalyst. The conditions were optimized by using 0.2 equiv. of the catalyst and 0.1 equiv. of formic acid in 2‐propanol at room temperature, which afforded the DA products in yields of up to 90% (exo/endo=5.5:1, 98% ee) with trans‐β‐nitrostyrene derivatives as the dienophiles. The structure/activity relationships of the bifunctional catalyst and the effects of the steric, electronic and hydrogen‐bonding properties of the dienophiles have been studied.     

Preparation the Key Intermediate of Angiotensin‐Converting Enzyme (ACE) Inhibitors: High Enantioselective Production of Ethyl (R)‐2‐Hydroxy‐4‐Phenylbutyrate with Candida boidinii CIOC21

Forty microorganisms belonging to different taxonomical groups were used to catalyze the enantioselective reduction of ethyl 2‐oxophenylbutyrate to afford the corresponding ethyl 2‐hydroxy‐4‐phenylbutyrate. Several microorganisms led to over 99% ee of ethyl (S)‐2‐hydroxy‐4‐phenylbutyrate. Especially, we firstly found that the Candida boidinii CIOC21 could be effectively used for the enantioselective preparation the ethyl (R)‐2‐hydroxy‐4‐phenylbutyrate in pure aqueous medium with 99% ee, a key intermediate in the production of angiotensin‐converting enzyme (ACE) inhibitors.     

Synthesis and characterization of degradable copoly(ester–amide)s: Poly(trans‐4‐hydroxy‐L‐proline‐co‐ε‐caprolactam)

Novel copolyesteramides were synthesized by reacting trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) with ε‐caprolactam (CLM) in the presence of stannous octoate [Sn(II) Oct.] as a catalyst. Various techniques, including ¹H‐NMR, IR, DSC, and viscosity, were used to elucidate structural characteristics and thermal properties of the resulting copolymers. Data showed that the optimal reaction condition for the synthesis of the copolymers was obtained by using 3 wt % Sn(II) Oct. at 170°C for 24 h. The DSC analysis demonstrated amorphous structure for most of the copolymers. The glass‐transition temperature of the copolymers shifts to a higher temperature with increasing Hpr/CLM molar ratio. In vitro degradation of these poly(N‐CBz‐Hpr‐co‐CLM)s was evaluated by weight loss measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1615–1621, 2002     

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) as a compatibilizer for cellulose acetate/poly(ε‐caprolactone) blends

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) (PVPVAc‐g‐PCL) was synthesized by radical copolymerization of N‐vinyl‐2‐pyrrolidone (VP)/vinyl acetate (VAc) comonomer and PCL macromonomer containing a reactive 2‐hydroxyethyl methacrylate terminal. The graft copolymer was designed in order to improve the interfacial adhesiveness of an immiscible blend system composed of cellulose acetate/poly(ε‐caprolactone) (CA/PCL). Adequate selections of preparation conditions led to successful acquisition of a series of graft copolymer samples with different values of molecular weight ( ), number of grafts (n), and segmental molecular weight of PVPVAc between adjacent grafts (M_n (between grafts)). Differential scanning calorimetry measurements gave a still immiscible indication for all of the ternary blends of CA/PCL/PVPVAc‐g‐PCL (72 : 18 : 10 in weight) that were prepared by using any of the copolymer samples as a compatibilizer. However, the incorporation enabled the CA/PCL (4 : 1) blend to be easily melt‐molded to give a visually homogeneous film sheet. This compatibilizing effect was found to be drastically enhanced when PVPVAc‐g‐PCLs of higher and M_n (between grafts) and lower n were employed. Scanning electron microscopy revealed that a uniform dispersion of the respective ingredients in the ternary blends was attainable with an assurance of the mixing scale of several hundreds of nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enzymatic Synthesis of 1‐Alkyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate Using a Novel Lysoplasmalogen‐Specific Phopholipase D

Many phospholipase Ds (PLDs) are known to catalyze transphosphatidylation as well as hydrolysis of phospholipids. Transphosphatidylation of lysoplasmalogen (LyPls)‐specific phospholipase D (LyPls‐PLD), which catalyzes hydrolysis of ether lysophospholipids such as LyPls and 1‐hexadecyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine (Lyso‐PAF), still remains unclear. This study aims to reveal the transphosphatidylation activity of LyPls‐PLD, that is, the production of cyclic ether lysophospholipid. The enzymatic reaction is conducted in a buffer system, and the reaction products of a novel LyPls‐PLD from Thermocrispum sp. are investigated using mass spectrometry (MS). MS analyses demonstrate the reaction products to consist of 100% 1‐hexadecyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate (cLyPA) and choline from Lyso‐PAF; however, 1‐alkenyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate from 1‐O‐1′‐(Z)‐octadecenyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine and 1‐O‐1′‐(Z)‐octadecenyl‐2‐hydroxy‐sn‐glycero‐3‐phosphoethanolamine is not produced. These results are expected to help in elucidating the catalytic mechanism of LyPls‐PLD, that is, the rate‐limiting step, and indicate LyPls‐PLD to be useful for the one‐pot synthesis of cLyPA. Practical Applications: A novel phospholipase D, LyPls‐PLD, can exclusively synthesize cLyPA from Lyso‐PAF using a one‐step enzymatic reaction without an organic solvent. cLyPA could be expected to show bioactivities similar to those of cyclic phosphatidic acid, which promotes normal cell differentiation, hyaluronic acid synthesis, antiproliferative activity in fibroblasts, and inhibitory activity toward cancer cell invasion and metastasis.     

Grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan

Poly(3‐hydroxy octanoate) (PHO), poly(3‐hydroxy butyrate‐co‐3‐hydroxyvalerate) (PHBV), and linoleic acid were grafted onto chitosan via condensation reactions between carboxylic acids and amine groups. Unreacted PHAs and linoleic acid were eliminated via chloroform extraction and for elimination of unreacted chitosan were used 2 wt % of HOAc solution. The pure chitosan graft copolymers were isolated and then characterized by FTIR, ¹³C‐NMR (in solid state), DSC, and TGA. Microbial polyester percentage grafted onto chitosan backbone was varying from 7 to 52 wt % as a function of molecular weight of PHAs, namely as a function of steric effect. Solubility tests were also performed. Graft copolymers were soluble, partially soluble or insoluble in 2 wt % of HOAc depending on the amount of free primary amine groups on chitosan backbone or degree of grafting percent. Thermal analysis of PHO‐g‐Chitosan graft copolymers indicated that the plastizer effect of PHO by means that they showed melting transitions T_ms at 80, 100, and 113°C or a broad T_ms between 60.5–124.5°C and 75–125°C while pure chitosan showed a sharp T_m at 123°C. In comparison of the solubility and thermal properties of graft copolymers, linoleic acid derivatives of chitosan were used. Thus, the grafting of poly(3‐hydroxyalkanoate) and linoleic acid onto chitosan decrease the thermal stability of chitosan backbone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:81–89, 2007     

Enantioselective Biooxidation of Racemic trans‐Cyclic Vicinal Diols: One‐Pot Synthesis of Both Enantiopure (S,S)‐Cyclic Vicinal Diols and (R)‐α‐Hydroxy Ketones

Highly regio‐ and enantioselective alcohol dehydrogenases BDHA (2,3‐butanediol dehydrogenase from Bacillus subtilis BGSC1A1), CDDHPm (cyclic diol dehydrogenase from Pseudomonas medocina TA5), and CDDHRh (cyclic diol dehydrogenase from Rhodococcus sp. Moj‐3449) were discovered for the oxidation of racemic trans‐cyclic vicinal diols. Recombinant Escherichia coli expressing BDHA was engineered as an efficient whole‐cell biocatalyst for the oxidation of (±)‐1,2‐cyclopentanediol, 1,2‐cyclohexanediol, 1,2‐cycloheptane‐diol, and 1,2‐cyclooctanediol, respectively, to give the corresponding (R)‐α‐hydroxy ketones in >99% ee and (S,S)‐cyclic diols in >99% ee at 50% conversion in one pot. Escherichia coli (BDHA‐LDH) co‐expressing lactate dehydrogenase (LDH) for intracellular regeneration of NAD⁺ catalyzed the regio‐ and enantioselective oxidation of (±)‐1,2‐dihydroxy‐1,2,3,4‐tetrahydronaphthalene to produce the corresponding (R)‐α‐hydroxy ketone in >99% ee and (S,S)‐cyclic diol in 96% ee at 49% conversion. Preparative biotransformations were also demonstrated. Thus, a novel and useful method for the one‐pot synthesis of both vicinal diols and α‐hydroxy ketones in high ee was developed via highly regio‐ and enantioselective oxidations of the racemic vicinal diols.

     

Effects of Temperature and Heating Time on the Formation of Four Toxic α,β‐Unsaturated‐4‐Hydroxyaldehydes in Vegetable Oils

The formation of four α,β‐unsaturated hydroxyaldehydes, 4‐hydroxy‐2‐trans‐hexenal (HHE), 4‐hydroxy‐2‐trans‐octenal (HOE), 4‐hydroxy‐2‐trans‐nonenal (HNE), and 4‐hydroxy‐2‐trans‐decenal (HDE), was detected in commercial corn, soybean, peanut, and canola oils heated for 1, 3, and 5 hours at 145, 165, and 185 °C. These four toxic aldehydes were investigated using high‐performance liquid chromatography (HPLC). These oils were selected based upon different degrees of unsaturations, especially their linoleic and linolenic acid concentrations. To select the appropriate conditions of temperatures and heating times, preliminary experiments were conducted using the thiobarbituric acid assay, which detects the formation of secondary‐oxidation products such as aldehydes and related carbonyl compounds. After various heat treatments, the formation of HHE, HOE, HNE, and HDE was detected as 2,4‐dinitrophenyl hydrazine derivatives using HPLC. In general, HHE, HOE, HNE, and HDE formation increased in all four oils with higher temperatures, longer heating times, and higher concentrations of linoleic and linolenic acids in the oils. The formation of HNE in the oils was mostly much higher than the other three 4‐hydroxyaldehyde isomers under the same conditions.     

Multi‐Enzymatic Synthesis of Optically Pure β‐Hydroxy α‐Amino Acids

A novel enzymatic production system of optically pure β‐hydroxy α‐amino acids was developed. Two enzymes were used for the system: an N‐succinyl L ‐amino acid β‐hydroxylase (SadA) belonging to the iron(II)/α‐ketoglutarate‐dependent dioxygenase superfamily and an N‐succinyl L ‐amino acid desuccinylase (LasA). The genes encoding the two enzymes are part of a gene set responsible for the biosynthesis of peptidyl compounds found in the Burkholderia ambifaria AMMD genome. SadA stereoselectively hydroxylated several N‐succinyl aliphatic L ‐amino acids and produced N‐succinyl β‐hydroxy L ‐amino acids, such as N‐succinyl‐L ‐β‐hydroxyvaline, N‐succinyl‐L ‐threonine, (2S,3R)‐N‐succinyl‐L ‐β‐hydroxyisoleucine, and N‐succinyl‐L ‐threo‐β‐hydroxyleucine. LasA catalyzed the desuccinylation of various N‐succinyl‐L ‐amino acids. Surprisingly, LasA is the first amide bond‐forming enzyme belonging to the amidohydrolase superfamily, and has succinylation activity towards the amino group of L ‐leucine. By combining SadA and LasA in a preparative scale production using N‐succinyl‐L ‐leucine as substrate, 2.3 mmol of L ‐threo‐β‐hydroxyleucine were successfully produced with 93% conversion and over 99% of diastereomeric excess. Consequently, the new production system described in this study has advantages in optical purity and reaction efficiency for application in the mass production of several β‐hydroxy α‐amino acids.

     

Synthesis of Amino Acid Conjugates and Further Derivatives of 3α‐Hydroxylup‐20(;29)ene‐23,28‐dioic acid

Triterpenes of betulinic acid type exhibit many interesting biological activities. Therefore a series of new 3α‐hydroxy‐lup‐20(29)‐ene‐23,28‐dioic acid derivatives 2a—22 with putative pharmacological activities were synthesized. As starting compounds 3α‐hydroxy‐lup‐20(29)‐ene‐23,28‐dioic acid ( 1a ), isolated from Schefflera octophylla, or its 3‐O‐acetyl derivative 1b were used. Mono‐ and diesters ( 2a—b from 1a , and 4d from 4c ) were prepared with CH₂N₂. Oxidation of the isopropenyl side chain with OsO₄ yielded the 20,29‐diols ( 4a—b from 1b , and 19 from 17 ), which were in the case of 4b further transformed to the 29‐norketones 8a/mdash;b . Oxidation of the isopropenyl side chain with m‐chloroperbenzoic acid afforded the 20,29‐epoxide 12 (from 1b ) and the 29‐aldehydes and a‐hydroxy aldehydes ( 13a—c from 2a, 14a—c from 2b , and 16a—c from 15a ). Ring A was modified by a tosylation—elimination sequence using p‐TsCl/NaOAc, which afforded diolefin 15a (from 2a ) with Δ^2,20(29) double bonds or 23‐nor‐Δ^3,20(29)diolefin 17 (from 1a ). Compounds 4b, 4c , and 8a were coupled with L ‐methionin, L ‐phenylalanin, L ‐alanin, L ‐serin, and L ‐glutaminic acid via amide bonds at positions 23 and 28 to afford the amino acid conjugates 5a—7b and 9a—11 .     

Decolourisation and treatment of pulp and paper mill effluent by lignin‐degrading Bacillus sp.

Three lignin‐degrading bacterial strains, identified as Paenibacillus sp., Aneurinibacillus aneurinilyticus and Bacillus sp. have been examined for the treatment of pulp and paper mill effluent. The results of this study revealed that all three bacterial strains effectively reduced colour (39–61%), lignin (28–53%), biochemical oxygen demand (BOD) (65–82%), chemical oxygen demand (COD) (52–78%) and total phenol (64–77%) within six days of incubation. However, the highest reduction in colour (61%), lignin (53%), BOD (82%) and COD (78%) was recorded by Bacillus sp. while, maximum reduction in total phenol (77%) was recorded with Paenibacillus sp. treatment. Significant reduction in colour and lignin content by these bacterial strains was observed after two days of incubation, indicating that bacterium initially utilized growth supportive substrates and subsequently chromophoric compounds thereby reducing lignin content and colour in the effluent. The total ion chromatograph (TIC) of compounds present in the ethyl acetate extract of control and bacterial treated samples revealed the formation of several lignin‐related aromatic compounds. The compounds identified in extracts of treated samples by Paenibacillus sp were t‐cinnamic acid and ferulic acid, while 3‐hydroxy‐4‐methoxyphenol, vanillic acid and vanillin acid by A. aneurinilyticus and gallic acid and ferulic acid by Bacillus sp. respectively indicating the degradation of lignin present in the effluent. The identified compounds obtained after different bacterial treatments were found to be strain‐specific. Among these identified compounds, ferulic acid, vanillic acid and vanillin could have immense value for their use in preservatives and in the food flavour industry. Copyright © 2007 Society of Chemical Industry     

Organocatalytic Asymmetric Mannich Reactions of 5H‐Oxazol‐4‐ones: Highly Enantio‐ and Diastereoselective Synthesis of Chiral α‐Alkylisoserine Derivatives

The first organocatalytic Mannich reaction of 5H‐oxazol‐4‐ones with various readily prepared aryl‐ and alkylsulfonimides has been developed. Two commercially available pseudoenantiomeric Cinchona alkaloids‐derived tertiary amine/ureas have been demonstrated as the most efficient catalysts to access the opposite enantiomers of the Mannich products with equally excellent enantio‐ and diastereoselectivities. From the Mannich adducts, important α‐methyl‐α‐hydroxy‐β‐amino acid derivatives, such as the α‐methylated C‐13 side chain of taxol and taxotere, can be conveniently prepared.