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Abstract: Breviones A–E ( 1–5 ), allelochemicals isolated from Penicillium brevicompactum Dierckx, are structurally unique diterpenoid derivatives. The first synthesis of both enantiomers of brevione B ( 2 ) was accomplished by employing the double SN2′-type tandem reaction as a key step, and the absolute configuration of the naturally occurring 2 was established. [Copyright &y& Elsevier]

Abstract: We developed an enzymatic resolution system for dl-pantoyl lactone that uses immobilized mycelia of Fusarium oxysporum, which produce a lactone-hydrolyzing enzyme (lactonase). The lactonase catalyzes the stereospecific hydrolysis of d-pantoyl lactone. One hundred eighty repeated batch reactions (total reaction time, 3780h) were made with mycelia entrapped in calcium alginate gels as the catalyst, in the presence of 90mM CaCl2. With a 300gl−1 dl-pantoyl lactone solution as the substrate, the hydrolysis rate for dl-pantoyl lactone was >40% and the optical purity of d-pantoic acid was 90% enantiomer excess. Immobilized mycelia retained 70% of their initial lactonase activity, even after 180 batch reactions. The estimated half-life of the lactonase activity of the immobilized mycelia was 6000h, which is 35 times higher than that of the free mycelia. The process has been exploited commercially since 1999. [Copyright &y& Elsevier]

Abstract: Recombinant epoxide hydrolase (EH) from Aspergillus niger can be a very promising tool for the resolution of various racemic epoxides by enantioselective hydrolysis. The enzyme was successfully immobilized by ionic adsorption onto DEAE-cellulose (99% yield, 70% of retention activity). The temperature for maximal activity (40°C) and the activation energy (38.8kJ/mol) were similar for both the immobilized and free EHs, whereas the optimal pH was about one unit less for the immobilized enzyme. Thermal stability was also affected by immobilization; the immobilized enzyme appeared to be slightly less stable than the free one. However, a gram-scale resolution of racemic para-chlorostyrene oxide (pCSO) was successfully carried out in a repeated batch reactor, operated for seven cycles. Furthermore, using a very high substrate concentration of 2M (306g/L), i.e. biphasic conditions, the resolution of 3g of pCSO was also achieved in a repeated batch reactor using approximately 300mg of immobilized EH, corresponding to less than 3mg of the enzymatic powder. [Copyright &y& Elsevier]

Abstract: The lipase PL-266 from Alcaligenes sp. catalyzed enantioselective acetylation of the decahydro-5,5,8a-trimethyl-2-oxo-naphthalene-1-methanol-2-ethylene acetal (±)-6 was carried out and an acetate (8aS)-7 and an alcohol (8aR)-6 possessing high enantiomeric excess (>98% ee), respectively, were obtained. Both (8aS)-7 and (8aR)-6 were converted to the (8aS)- and (8aR)-decahydro-5,5,8a-trimethyl-2-oxo-naphthalene-1-carboxylates (4), respectively. The (8aR)-β-keto ester (4) was converted to the important intermediate (8aR)-16 for the synthesis of natural hyatellaquinone (3). [Copyright &y& Elsevier]

Synthetic applications of lipases from Candida rugosa (CRL) and Pseudomonas sp. (PSL) immobilized on poly(ethylene oxide) (PEO) were studied. The morphology and thermal properties of the lipases immobilized on the support were analyzed by microscopy and thermal analysis techniques. To evaluate the efficiency of these systems, the esterification reaction of lauric acid (5 mmol) with n-pentanol (5 mmol) was studied. Reactional parameters such as time, temperature, enzyme concentration and organic media (n-hexane) were evaluated. The degree of esterification increased as a function of time, temperature and concentration. The influence of organic solvents (n-hexane, cyclohexane, n-heptane and acetone) was also considered for this reaction using a CRL/PEO system. The enzymatic resolutions of (R,S)-2-octanol, (R,S)-2-(4-chlorophenoxy) propionic and (R,S)-2-bromo hexanoic acids were also studied. The R-alcohol was obtained with enantiometric excess of product (eep) >98% (E=180). For the resolution of racemic acids, the enantiomeric excess for the substrate (ees) values were in the range 1–76% and the eep values were in the range 6–96% (E=1, 1–118). [Copyright &y& Elsevier]

Abstract: Synthesis and synthetic utilities of stereocontrolled α,α-difluoro-β-hydroxy-γ,δ-unsaturated carbonyl compounds via enzymatic resolution with lipase PS (Pseudomonas cepacia, Amano Pharmaceutical Co. Ltd.) or lipase MY (Candida rugosa, Meito Sangyo Co. Ltd.) were described, and then the absolute configuration of obtained chiral materials was determined by the modified Mosher''s method. [Copyright &y& Elsevier]

Presents a study on thermostable esterase from a thermoacidophilic archaeon. Methods used for the identification of homolog to lipolytic enzymes having the consensus sequence Gly-X-Ser-X-Gly; Broad substrate specificities toward various p-nitrophenyl esters ranging from C2 to C16; Results that indicate S. solfataricus esterase can be used for application in the synthesis of chiral compounds.

Kinetic resolution of a chiral alcohol, 4-hydroxy-3-methyl-2-(2′-propenyl)-2-cyclopentenone (HMPC), a key intermediate for the production of prallethrin insecticides, was successfully carried out by enantioselective hydrolysis of (RS)-HMPC acetate using calcium alginate gel-entrapped cells of a newly isolated esterase-producing bacterium Acinetobacter sp. CGMCC 0789. When the effect of different cosolvents was investigated, it was found that isopropanol could markedly enhance the activity and enantioselectivity of the immobilized cells. The optimum concentration of isopropanol was 10% (v/v) where immobilized cells still showed good operational stability. After 10 cycles of reaction, no significant decrease in the enzyme activity was observed. The catalytic specificity constants (Vmax/Km) for both enantiomers of the substrate were determined with partially purified enzyme, giving 0.0184 and 0.671 h-1 for the (S)- and (R)-ester, respectively. [Copyright &y& Elsevier]

Fusarium moniliforme CGMCC 0536 showing excellent stereoselective d-pantonohydrolase activity was immobilized by cross-linking with glutaraldehyde. Various characteristics of immobilized cells were assessed. Optimum conditions for enzyme activity were not affected after cross-linking, and the pH and temperature for both free and cross-linked cells were found to be pH 7.5 and 55 °C, respectively. The Km value of cross-linked cells (118 mM) was slightly higher than that of free cells (96 mM), while the Vmax value decreased from 4.18 to 3.87 mM min-1 g-1 wet cells after cross-linking. Compared with the free cells, the half-life of cross-linked cells was noticeably increased, and the operational stability of the biocatalyst for recycling in batch processes was markedly improved (no obvious decrease after 110 times). [Copyright &y& Elsevier]

A novel spectrophotometric method for the determination of tryptophan (Trp) has been proposed. The sensitive and simple method was based upon the finding that NaNO2 and Trp formed a diazotized product in nitric acid medium, and that a bright magenta color developed for the product on coupling to N-(1-naphthyl) ethylenediamine dihydrochloride (NEDA) which was stable for at least 40 min. The absorption maximum was observed at 550 nm, and the apparent molar absorptivity was 8.48×103 L·mol-1·cm-1. A linear dependence of absorbance on Trp concentration allowed sensitive quantification of Trp over the range of 1–20 µg mL-1, and the detection limit was 0.5 µg mL-1. The method has been successfully applied to the determination of L-Trp in the DL-N-acetyltryptophan enzymatic resolution system. The relative standard deviations (n=6) and recoveries were found to be 0.97–2.21% and 97.5–101.3%, respectively. The accuracy of the new method was confirmed by the results from capillary electrophoresis. Furthermore, the interference study showed that DL-N-acetyltryptophan (substrate), CoCl2 (activator), and other common amino acids did not exhibit any detectable interference with Trp determination. [ABSTRACT FROM AUTHOR]

The two processes for the partial purification and for the immobilization of a crude lipase preparation (Candida rugosa Lipase OF) have been successfully integrated into one by simple adsorption of the enzyme onto a cation ion exchanger resin (SP-Sephadex C-50) at pH 3.5. Due to selective removal of the unfavorable lipase isoenzyme (L1), the enzyme components (mainly L2 and L3) that are tightly fixed on the resin displayed a significantly improved enantioselectivity (E value: 50 versus 13 with addition of Tween-80) in the biocatalytic hydrolysis of 2-chloroethyl ester of rac-ketoprofen. The activity yields of the immobilized lipase were 48 and 70%, respectively when emulsified and non-emulsified substrates were employed for enzyme assay. Moreover, the concentration of Tween-80 was found to be a factor affecting the lipase enantioselectivity. By using such an immobilized enzyme as biocatalyst, the process for preparing enantiopure (S)-ketoprofen becomes simpler and more practical as compared with the previously reported procedures and the product was obtained with >94% ee at 22.3% conversion in the presence of an optimal concentration (0.5 mg/ml) of Tween-80 at pH 3.5. Furthermore, the operational stability of the immobilized biocatalyst was examined in different types of reactors. In an air-bubbled column reactor, the productivity was much higher than that in a packed-bed column reactor, in spite of a slightly lower stability. Under optimal conditions, the air-bubbled column reactor could be operated smoothly for at least 350 h, remaining nearly 50% activity. [Copyright &y& Elsevier]

A highly enantioselective (R)-ester hydrolase was partially purified from a newly isolated bacterium, Acinetobacter sp. CGMCC 0789, whose resting cells exhibited a highly enantioselective activity toward the acetate of (4R)-hydroxy-3-methyl-2-(2-propynyl)- cyclopent-2-enone (R-HMPC). The optimum pH and temperature of the partially purified enzyme were 8.0 and 60 °C, respectively. The enantioselectivity of the crude enzyme was increased by 1.2-fold from 16 to 20 when the reaction temperature was raised from 30 to 60 °C. The activity of the crude enzyme was enhanced by 4.1-fold and the enantioselectivity (E-value) was markedly enhanced by 4.3-fold from 16 to 68 upon addition of a cationic detergent, benzethonium chloride [(diisobutyl phenoxyethoxyethyl) dimethyl benzylammoniom chloride]. The hydrolysis of 52 mM (R,S)-HMPC acetate to (R)-HMPC was completed within 8 h, with optical purity of 91.4% eep and conversion of 49%. [Copyright &y& Elsevier]

(R)-(+)-Paraconic acid 4, (S)-(−)-terebic acid 6 and their corresponding methyl and ethyl esters having ee’s ranging from 60% to 92% were obtained by enzymatic resolution of their racemates. The enzymatic resolution of racemic ethyl γ-methylparaconates 14a and 14b allowed the isolation of the unreacted ester (2R,3R)-(+)-14a and that of the lactonic acid (2S,3R)-(−)-5b with 80% and 93% ee, respectively, the former by the use of Horse liver acetone powder (HLAP), the latter using α-chymotrypsin (α-CT). The enantiomeric ethyl (2S,3S)-(−)-14a and (2S,3R)-(−)-14b, both with >99% ee, were obtained by baker’s yeast reduction of diethyl acetylsuccinate. [Copyright &y& Elsevier]

Lipases were used for the resolution of (±) (4aR, 7R, 8aS)-2-phenyl-4a,7,8,8a-tetrahydro-4H-1,3-benzodioxine. This separation was carried out on preparative scale and used for the synthesis of eight phosphoramidites of cyclohexenyl nucleosides (d- and l-series). [Copyright &y& Elsevier]

A series of (R)- and (S)-3-aminomethyl-1-tetralones, conformationally constrained analogues of haloperidol, have been obtained by enzymatic resolution of the corresponding racemic 3-hydroxymethyl-1-tetralones using Pseudomonas fluorescens lipase. Their binding affinities at dopamine D2 and serotonin 5-HT2A and 5-HT2C receptors were determined showing in some cases an atypical antipsychotic profile with Meltzer''s ratio higher than 1.30. [Copyright &y& Elsevier]

Chemo-enzymatic approaches for the synthesis of the family of aromatase inhibitory drug via lipase-catalyzed kinetic resolution of (±)-4-cyano-4-phenyl-1-hexanol (2) as appropriate precursors were described. Enzymatic transesterification of primary alcohol (±)-2 using Pseudomonas cepacia (Amano PS, PCL) provided the enantiopure alcohol (R)-(−)-2 with 99% ee at conversion of 86%, while that of (±)-2 using Pseudomonas fluorescens (Amano AK, LAK) provided the (S)-(+)-2 with 96% ee at conversion of 86%. Chemical transformation of substrate (R)-(−)-2 gave (R)-(+)-aminoglutethimide (1) in enantioselectively high yield. [Copyright &y& Elsevier]

The borane adduct of (2-hydroxypropyl)diphenylphosphane 1 was resolved by enantioselective esterification with CAL-B. (S)-1 was thus obtained with 91% enantiomeric excess. Its absolute configuration was determined by chemical correlation from (S)-propylene oxide. [Copyright &y& Elsevier]

The total synthesis of (−)-(8R, 10S)- and (+)-(8S, 10R)-8-hydroxypolypoda-13,17,21-triene (1) was achieved based on the kinetic resolution of (±)-epoxy-albicanol (3) using lipase. The absolute structure of natural product (1) was synthetically again confirmed to be (5S, 8R, 9R, 10S)-8-hydroxypolypoda-13,17,21-triene. [Copyright &y& Elsevier]

A synthetic strategy based upon three basic reactions—enzymatic resolution, oxygen–sulfur exchange, reduction—allowed us to carry out an easy and useful synthesis of a series of new 1,4-sulfanylalcohols from aliphatic γ-lactones. Final products have been obtained in good yields with enantiomeric excesses in a 66–91% range. [Copyright &y& Elsevier]

A new ionic liquid, N-ethyl pyridinium trifluoroacetate, was used with a commercial protease to resolve N-acetyl amino acid esters in place of traditional organic solvents. Products with enantiomeric excess (ee) between 86–97% were obtained. These results show that with low concentration of this new ionic liquid, the enzymatic resolution can be increased considerably depending upon the substrate being used. [ABSTRACT FROM AUTHOR]

The convergent synthesis of a potent α[sub 1A] -selective adrenoceptor antagonist is described. Salient features of the synthesis include the enzymatic resolution of a racemic dihydropyrimidinone and the use of a palladium coupling reaction in the synthesis of 2,4'-dipyridyl.Key words: dihydropyrimidinone, enzymatic resolution, palladium coupling.Voici la description de la synthèse convergente d'un puissant antagoniste α[sub 1A] -sélectif au récepteur adrénergique (adrénorécepteur). Les principales caractéristiques de cette synthèse incluent notamment la résolution enzymatique d'un dihydropyrimidinone racémique et l'utilisation d'une réaction de couplage catalysée par le palladium dans la synthèse du 2,4'-dipyridyle.Mots clés : dihydropyrimidinone, résolution enzymatique, couplage par le palladium.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A study aimed to select efficient epoxide hydrolases (EHs) allowing to achieve the enzymatic resolution of 2-, 3- and 4-pyridyloxirane (1–3) has been achieved, using 2-pyridyloxirane 1 as test substrate. Five thus selected EH-sources that showed interesting enantioselectivity were looked at in more detail for the conversion of 1–3. [Copyright &y& Elsevier]

2-(Substituted phenoxy)-1-propanols, e.g. 2-(4-chlorophenoxy)-1-propanol, belonging to primary alcohols with an oxygen atom at the stereocenter, were resolved with moderate to good enantioselectivity, as judged by the value of enantiomeric ratio E (up to 27), through the enantioselective acylation with vinyl butanoate mediated by the little-known lipase from Achromobacter sp. in diisopropyl ether, after the examination of potential factors affecting the reaction such as organic solvents and acyl donors. [ABSTRACT FROM AUTHOR]

Four stereoisomers of centrolobine, (3 R ,7 S )-(−)-centrolobine ( 1 ), (3 S ,7 S )-(−)- epi -centrolobine ( 2 ), (3 S ,7 R )-(+)-centrolobine ( 3 ), and (3 R ,7 R )-(+)- epi -centrolobine ( 4 ) have been achieved in an efficient manner in 24–28% overall yield over 9–10 linear steps starting from cheap and commercially available 4-methoxybenzaldehyde following chemoenzymatic protocol. The key features of this synthetic protocol are enzymatic resolution, cross-metathesis (CM), and our own developed tandem isomerization followed by C–O and C–C bond formation reaction. [ABSTRACT FROM AUTHOR]

Synthesis of nitrosporeusines A and B, thioester-bearing alkaloids from the Arctic Streptomyces nitrosporeus with exceptional biological activity is disclosed for the first time. In addition, we have prepared another biologically important natural product, maleimycin, in optically pure form using a gram-scale enzymatic resolution method. [ABSTRACT FROM AUTHOR]

The present review outlines recent examples of enzyme-based resolution procedures for amino acids via the hydrolysis of their esters. The resolutions have been achieved by using proteases ( α-chymotrypsin, subtilisin and other microbial proteases, and sulfhydryl proteases of plant origin) and lipases. Relevant work utilizing yeast and other microbial cells is also included. [ABSTRACT FROM AUTHOR]

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Papain-catalyzed regioselective cleavage of α-methyl ester in Z-DL-Asu(OMe)-OMe leads to Z-L-Asu(OMe)-OH and Z-D-Asu(OMe)-OMe. Subsequent saponifications yield Z-L-Asu-OH and Z-D-Asu-OH. The enzymatic α-ester hydrolysis was also achieved by subtilisin BPN′ in organic solvent with low water content. [ABSTRACT FROM AUTHOR]

A new approach toward the synthesis of the hydrophobic moiety of rhamnolipid derivatives has been developed, involving two key cross-metatheses and an unusual Mitsunobu reaction. Small structural variations of the side chains should enable a better understanding of the role of the lipid moiety in immunostimulatory and plant defense eliciting properties. [ABSTRACT FROM AUTHOR]

Both the isomers methyl-(2S,8R)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate and methyl-(2S,8S)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate of an unusual amino acid residue and the key fragment of microsporin B are prepared. The key steps include cross metathesis and enzymatic kinetic resolution. In addition, a linear tetrapeptide with desired components towards total synthesis is also reported. [ABSTRACT FROM AUTHOR]

Furan-2-carboxylic acid was used as a starting material for the synthesis of dehydro-homopilopic acid. Esterification, hydrogenation and enzymatic hydrolysis followed by the reduction of Weinreb amides and a single-step attachment of a 1-methyl-imidazole residue allowed for the concise synthesis of both enantiomers of pilocarpine. [ABSTRACT FROM AUTHOR]

Abstract: (−)-Lardolure and (2R,4R,6R,8R)-2,4,6,8-tetramethylundecanoic acid have been synthesized via lipase catalyzed desymmetrization strategy to create two methyl chiral centers. Other key steps involved in the synthesis are Wittig reaction, Evan’s asymmetric alkylation, Grignard reaction, Pd-catalyzed isomerization of primary allylic alcohol to corresponding saturated aldehyde, and PhNO/proline catalyzed MacMillan α-hydroxylation. [Copyright &y& Elsevier]

A versatile procedure for the synthesis of optically pure 1-amino-3-aryl indanes is presented, exemplified by the synthesis of the triple uptake inhibitor (+)-indatraline (1). [ABSTRACT FROM AUTHOR]

Abstract: A direct asymmetric synthesis of a trans-4,5-difunctionalised cyclopentenone derivative has been achieved in 55% yield and 80% ee by organocatalysed rearrangement of a pyranone in tert-butanol by DABCO with simultaneous enzymatic resolution. [Copyright &y& Elsevier]

A synthesis of the banana weevil pheromone component (1S,3R,5R,7S)-sordidin starting from (S)-2-(2-ethyl-1,3-dioxolanyl)propan-1-ol and (R)-4-hydroxypentan-2-one is described. No epimerization was observed for the final, intramolecular, acid-catalyzed cyclization step using aqueous oxalic acid. [ABSTRACT FROM AUTHOR]

The first synthesis of glaucescenolide (), a cytotoxic sesquiterpene isolated from the liverwort, Schistochila glaucescens, was achieved by starting from 2,2,6-trimethylcyclohexanone (). The absolute configuration of the naturally occurring was confirmed as 5S,7S,10R. [Copyright &y& Elsevier]

A method of synthesizing optically pure (S)-2-acetylthio-3-benzenepropanoic acid has been developed and good to excellent enantiomeric excess achieved via enzymatic resolution. [Copyright &y& Elsevier]

Both enantiomers of 3-(3-indolyl)butyric acid, a key intermediate of indolmycin, were successfully prepared by lipase-catalysed enantioselective hydrolysis. Of the enzymes examined, Pseudomonas fluorescens lipase (lipase AK) showed the best enantioselectivity and highest reactivity for the hydrolysis of (±)-trifluoroethyl 3-(3-indolyl)butyrate. Under optimal conditions, optical resolution was completed in one enzyme-catalysed step, the S-acid and unreacted R-ester being obtained in high optical purity. [ABSTRACT FROM AUTHOR]