Microbial metabolism of 2-arylpropionic acids: Chiral inversion of ibuprofen and 2-phenylpropionic acid

The metabolism of (R,S)-ibuprofen has been investigated in 24 microbial cultures. Of these Cunninghamella elegans, Mucor hiemalis, and Verticillium lecanii catalyzed the oxidation of the drug to 2-[4-(2-hydroxy-2-methylpropyl)phenyl]propionic acid, a known mammalian metabolite. The extent of metabolism was greatest with V. lecanii, with some 47% of the substrate being consumed over a 7-day incubation period. Enantiomeric analysis indicated stereoselective metabolism of (R)-ibuprofen, the enantiomeric composition of the residual substrate being R/S = 0.25. Following a preparative scale incubation of (R,S)-ibuprofen with V. lecanii, in which the reaction was allowed to go to completion, the metabolite was found to be predominantly of the S-configuration (S/R = 2.1), suggesting that chiral inversion of either the drug and/or the metabolite had taken place. Analysis of extracts following incubation of (R,S)-, (R)-, and (S)-2-phenylpropionic acid with V. lecanii, for 21 days, indicated that chiral inversion of the (R)-enantiomer to its optical antipode had taken place. The results of these investigations indicate that microorganisms, in addition to mammals, are able to mediate the chiral inversion of 2-arylpropionic acids. This observation may have implications for the preparation of optically pure 2-arylpropionic acids. © 1993 Wiley-Liss, Inc.     

Chiral synthesis of (2S,3S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol

Resolution of (2RS,3RS)-2-[alpha-(2-methoxymethoxyphenoxy)phenylmethyl]morpholine, 11, with (+) mandelic acid led to the formation of (+)-(2S,3S)-2-[alpha-(2-methoxymethoxyphenoxy)phenyl methyl] morpholine (11a). Compound 11 was synthesized in seven steps from (2RS,3RS)-cinnamyl alcohol-2,3-epoxide (4), with an overall yield of 17%. Cleavage of the methoxymethyl group of the Fmoc derivative 12 with catalytic amounts of p-toluenesulfonic acid in methanol afforded (+)-(2S,3S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol 2. The synthetic utility as well as the configuration of compound 2 has been demonstrated by converting (S,S)-2-(2-morpholin-2-yl-2-phenylmethoxy)phenol 2 to (2S,3S)-2-[alpha-(2-ethoxyphenoxy)phenylmethyl]morpholine (1) and (2S,3S)-2-(2-methoxyphenoxy) benzyl)morpholine (16), two potential norepinephrine reuptake inhibitors under clinical evaluation.     

Synthesis and absolute configuration of the stereoisomers of [2-(1-diethylaminopropyl)] 1-hydroxy-1,1′-bicyclohexyl-2-carboxylate,a muscarinic antagonist

The compound [2-(1-diethylaminopropyl)] 1-hydroxy-1,1′-bicyclohexyl-2-carboxylate 1 is a muscarinic antagonist characterized by the presence of three chiral atoms and eight possible stereoisomers. The binding affinities to the five cloned m₁–m₅ muscarinic receptors of the stereoisomers of 1 were previously investigated and proved to be related to the chirality of the molecules. The eight isomers are prepared through the synthesis of their racemates followed by chemical resolution as (+) and (−) tartrate or (+) and (−) dibenzoyltartrate salts. The isomers with cis-configuration of OH and COOH substituents of the cyclohexane are also obtained by coupling optically active (1S, 2S) or (1R,2R)-1-hydroxy-[1,1′-bicyclohexyl]-2-carboxylic acid with (S)- or (R)-1-diethylamino-2-propanol. Chiral GC and HPLC methods are used to determine their optical purity. The absolute configurations of the four cis- and four trans-isomers are established by stereospecific synthesis and X-ray crystallographic data. Chirality 9:713–721, 1997. © 1997 Wiley-Liss, Inc.     

N-(n-Butylamide) of (S)-2-(phenylcarbamoyloxy)propionic acid: A new chiral solvating agent,derived from L-lactic acid,for the enantiomeric purity determination of derivatized amino acids

The N-(n-butylamide) of (S)-2-(phenylcarbamoyloxy)propionic acid, easily prepared starting from the inexpensive L -ethyl lactate, can be used as convenient chiral solvating agent (CSA) to determine the enantiomeric composition of N-(3,5-dinitrobenzoyl)amino acid methyl esters.     

Preparation of Single-Enantiomer Biofunctional Molecules with (S)-2-Methoxy-2-(1-naphthyl)propanoic Acid

(RS)-β-Ionol and (RS)-2-methyl-4-octanol were resolved by using (S)-2-methoxy-2-(1-naphthyl)propanoic acid [(S)-MαNP acid]. The specific stereochemistry of each MαNP ester was elucidated by 2D NMR analyses, and shielding by the 1-naphthyl group was observed in both the ¹H- and ¹³C-NMR spectra. Solvolysis of the individual (S)-MαNP esters gave four single-enantiomer alcohols. The normal-phase HPLC elution order of each MαNP ester is also discussed.     

Formation of glycine conjugate and (-)-(R)-enantiomer from (+)-(S)-2-phenylpropionic acid suggesting the formation of the CoA thioester intermediate of (+)-(S)-enantiomer in dogs.

It has been proposed that the chiral inversion of the 2-arylpropionic acids is due to the stereospecific formation of the (-)-R-profenyl-CoA thioesters which are putative intermediates in the inversion. Accordingly, amino acid conjugation, for which the CoA thioesters are obligate intermediates, should be restricted to those optical forms which give rise to the (-)-R-profenyl-CoA, i.e., the racemates and the (-)-(R)-isomers. We have examined this problem in dogs with respect to 2-phenylpropionic acid(2-PPA). Regardless of the optical configuration of 2-phenylpropionic acid administered, the glycine conjugate was the major urinary metabolite and this was shown to be exclusively the (+)-(S)-enantiomer by chiral HPLC. Both (-)-(R)- and (+)-(S)-2-phenylpropionic acid were present in plasma after the administration of either antipode, and further evidence of the chiral inversion of both enantiomers was provided by the presence of some 25% of the opposite enantiomer in the free 2-phenylpropionic acid and its glucuronide excreted in urine after administration of (-)-(R)- and (+)-(S)-2-phenylpropionic acid. The (+)-(S)-enantiomer underwent chiral inversion to the (-)-(R)-antipode when incubated with dog hepatocytes. These data suggests that both enantiomers of 2-phenylpropionic acid are substrates for canine hepatic acyl CoA ligase(s) and thus undergo chiral inversion, but that the CoA thioester of only (+)-(S)-2-phenylpropionic acid is a substrate for the glycine N-acyl transferase. These studies are presently being extended to the structure and species specificity of the reverse inversion and amino acid conjugation of profen NSAIDs.     

Characterization of the CHORI-240 BAC clones containing the bovineCSN1S1, CSN2, STATH, CSN1S2 andCSN3 genes

Nineteen BAC clones were identified by hybridization of the bovine genomic BAC library CHORI-240 with mixedCSN1S1- andCSN3-specific probes. Two of the clones were shown to contain the genesCSN1S1, CSN1S2, CSN2, STATH andCSN3, and five were proved to include the genesCSN2, STATH, CSN1S2 andCSN3. These data showed that the BAC contig was established for the whole casein cluster, including all known five genes.     

Field response of the pine sawfly Neodiprion sertifer to the pheromone (2S,3S,7S)-diprionyl acetate and its stereoisomers

All eight optical isomers of 3,7-dimethyl-2-pentadecanyl acetate (diprionyl acetate), of high optical purity (> 97.4%), were tested for a behavioural activity on male pine sawflies, Neodiprion sertifer (Geoffr.) (Hymenoptera: Diprionidae), in northern Europe. Males were strongly attracted to (2S,3S,7S)-diprionyl acetate. Addition of more than 0.1% of the (2S,3R,7R)-isomer reduced the catch and above 2% the attraction was completely inhibited. Contrary to what has been reported for North American and Japanese populations, so significant synergistic effect of small amounts of the (2S,3R,7R)-isomer could be demonstrated. The effects of addition of the other six optical isomers alone or in combinations, were also studied, but none was found to be a synergist. The (2S,3R,7S)-isomer had a weak inhibitory effect, and completely inhibited the attraction to the (2S,3S,7S)-isomer when applied in about equal amounts as the attractant. In some cases a reduction in catch was noted when other isomers were tested, but this could be attributed to the very small amounts of the inhibitory (2S,3R,7R)-isomer present in these isomers.     

Improved resolution of (±)-trans-2'-hydroxy-5,9-dimethyl-6,7-benzomorphans

An efficient resolution of (±)-trans-2'-hydroxy-5,9-dimethyl-6,7-benzomorphan has been developed employing (—)-(R)- and (+)-(S)-O-acetylmandelic acids. Measurement of optical rotations on the resolved bases, NMR analyses of diastereomeric urea derivatives, as well as gas chromatographic analyses of diastereomeric amide derivatives indicate a net improvement over previous resolution methodology and an enantiomeric excess ≥ 99%. © 1992 Wiley-Liss, Inc.     

Enantioresolution of Chiral Derivatives of Xanthones on (S,S)‐Whelk‐O1 and l‐Phenylglycine Stationary Phases and Chiral Recognition Mechanism by Docking Approach for (S,S)‐Whelk‐O1

The resolution of seven enantiomeric pairs of chiral derivatives of xanthones (CDXs) on (S,S)‐Whelk‐O1 and l ‐phenylglycine chiral stationary phases (CSPs) was systematically investigated using multimodal elution conditions (normal‐phase, polar‐organic, and reversed‐phase). The (S,S)‐Whelk‐O1 CSP, under polar‐organic conditions, demonstrated a very good power of resolution for the CDXs possessing an aromatic moiety linked to the stereogenic center with separation factor and resolution factor ranging from 1.91 to 7.55 and from 6.71 to 24.16, respectively. The chiral recognition mechanisms were also investigated for (S,S)‐Whelk‐O1 CSP by molecular docking technique. Data regarding the CSP–CDX molecular conformations and interactions were retrieved. These results were in accordance with the experimental chromatographic parameters regarding enantioselectivity and enantiomer elution order. The results of the present study fulfilled the initial objectives of enantioselective studies of CDXs and elucidation of intermolecular CSP–CDX interactions. Chirality 25:89–100, 2013. © 2012 Wiley Periodicals, Inc.     

No evidence from FTIR difference spectroscopy that glutamate-189 of the D1 polypeptide ligates a Mn ion that undergoes oxidation during the S0 to S1, S1 to S2, or S2 to S3 transitions in photosystem II

In the recent X-ray crystallographic structural models of photosystem II, Glu189 of the D1 polypeptide is assigned as a ligand of the oxygen-evolving Mn(4) cluster. To determine if D1-Glu189 ligates a Mn ion that undergoes oxidation during one or more of the S(0) --> S(1), S(1) --> S(2), and S(2) --> S(3) transitions, the FTIR difference spectra of the individual S-state transitions in D1-E189Q and D1-E189R mutant PSII particles from the cyanobacterium Synechocystis sp. PCC 6803 were compared with those in wild-type PSII particles. Remarkably, the data show that neither mutation significantly alters the mid-frequency regions (1800-1200 cm(-)(1)) of any of the FTIR difference spectra. Importantly, neither mutation eliminates any specific symmetric or asymmetric carboxylate stretching mode that might have been assigned to D1-Glu189. The small spectral alterations that are observed are similar in amplitude to those that are observed in wild-type PSII particles that have been exchanged into FTIR analysis buffer by different methods or those that are observed in D2-H189Q mutant PSII particles (the residue D2-His189 is located >25 A from the Mn(4) cluster and accepts a hydrogen bond from Tyr Y(D)). The absence of significant mutation-induced spectral alterations in the D1-Glu189 mutants shows that the oxidation of the Mn(4) cluster does not alter the frequencies of the carboxylate stretching modes of D1-Glu189 during the S(0) --> S(1), S(1) --> S(2), or S(2) --> S(3) transitions. One explanation of these data is that D1-Glu189 ligates a Mn ion that does not increase its charge or oxidation state during any of these S-state transitions. However, because the same conclusion was reached previously for D1-Asp170, and because the recent X-ray crystallographic structural models assign D1-Asp170 and D1-Glu189 as ligating different Mn ions, this explanation requires that (1) the extra positive charge that develops on the Mn(4) cluster during the S(1) --> S(2) transition be localized on the Mn ion that is ligated by the alpha-COO(-) group of D1-Ala344 and (2) any increase in positive charge that develops on the Mn(4) cluster during the S(0) --> S(1) and S(2) --> S(3) transitions be localized on the one Mn ion that is not ligated by D1-Asp170, D1-Glu189, or D1-Ala344. An alternative explanation of the FTIR data is that D1-Glu189 does not ligate the Mn(4) cluster. This conclusion would be consistent with earlier spectroscopic analyses of D1-Glu189 mutants, but would require that the proximity of D1-Glu189 to manganese in the X-ray crystallographic structural models be an artifact of the radiation-induced reduction of the Mn(4) cluster that occurred during the collection of the X-ray diffraction data.     

Copper(II) complexes of N2-alkyl-(S)-amino acid amides as chiral selectors for dynamically coated chiral stationary phases in RP-HPLC

Copper(II) complexes of N²-octyl-(S)-phenylalaninamide (Noc-Phe-NH₂), N²-dodecyl-(S)-phenylalaninamide (Ndo-Phe-NH₂), and N²-octyl-(S)-norleucinamide (Noc-NLeu-NH₂), dynamically adsorbed on a reversed-phase C₁₈ column, were able to perform the direct enantiomeric separation of unmodified amino acids, amino acid amides and esters, hydroxy acids, and dipeptides by elution with aqueous or mixed aqueous-organic solutions containing copper(II) sulphate or acetate. The role played by several parameters in the separation procedure was examined with the copper(II) complex of Noc-Phe-NH₂ [concentration of the copper(II) ion in the eluent, pH and eluent polarity, amount of adsorbed selector]. The separation was shown to occur entirely on the stationary phase. The mechanism of chiral discrimination is discussed in terms of the chromatographic parameters and of the structure of the copper(II) complexes in solution and in the solid state. The chiral stationary phase maintained its separation ability for about 3 months. However, the column could be easily restored by recovering the selector with methanol and repeating the loading procedure. © 1996 Wiley-Liss, Inc.     

Chiral nuclear magnetic resonance shift reagents: Lanthanide mixtures with 1-(1-naphthyl) ethylurea derivatives of amino acids

Esters of 1-(1-naphthly)ethylurea derivatives of L-valine, L-leucine, L-tert-leucine, and L-proline are examined as organic-soluble chiral nuclear magnetic resonance (NMR) resolving agents. The reagents are useful for resolving the spectra of chiral sulfoxides, amines, alcohols, and carboxylic acids. Enantiomeric resolution is caused by a combination of diastereomeric effects and the different association constants of the substrates with the resolving agents. Organic-soluble lanthanide species are added to resolving agent-substrate mixtures and often enhance the enantiomeric resolution. The enhancement occurs because the substrate that exhibits weaker binding with the resolving agent is more available to bond to the lanthanide. Broadening in the spectra with lanthanides is reduced at 50°C. Enantiomeric resolution is still observed at elevated temperatures. Chirality 9:1–9, 1997. © 1997 Wiley-Liss, Inc.     

The Combined Deletion of S6K1 and Akt2 Deteriorates Glycemic Control in a High-Fat Diet

Signaling downstream of mechanistic target of rapamycin complexes 1 and 2 (mTORC1 and mTORC2) controls specific and distinct aspects of insulin action and nutrient homeostasis in an interconnected and as yet unclear way. Mice lacking the mTORC1 substrate S6 kinase 1 (S6K1) maintain proper glycemic control with a high-fat diet. This phenotype is accompanied by insulin hypersensitivity, Akt- and AMP-activated kinase upregulation, and increased lipolysis in adipose tissue and skeletal muscle. Here, we show that, when S6K1 inactivation is combined with the deletion of the mTORC2 substrate Akt2, glucose homeostasis is compromised due to defects in both insulin action and β-cell function. After a high-fat diet, the S6K1(-/-) Akt2(-/-) double-mutant mice do not become obese, though they are severely hyperglycemic. Our data demonstrate that S6K1 is required for pancreatic β-cell growth and function during adaptation to insulin resistance states. Strikingly, the inactivation of two targets of mTOR and phosphatidylinositol 3-kinase signaling is sufficient to reproduce major hallmarks of type 2 diabetes.     

Direct determination of the enantiomeric purity of (R)- and (S)-2-hydroxy-4-phenylbutyric acid

The determination of enantiomeric purity of (R)- and (S)-2-hydroxy-4-phenylbutyric acid by chiral HPLC is described. Good resolution has been obtained on covalently bonded L-hydroxyproline saturated with Cu(II) ions. The method makes possible the determination of enantiomeric purity in media containing growing cells. © 1994 Wiley-Liss, Inc.     

Optimization of APE1547-catalyzed enantioselective transesterification of (R/S)-2-methyl-1-butanol in an ionic liquid

Aeropyrum pernix esterase (APE1547) was successfully used to catalyze the enantioselective transesterification of (R/S)-2-methyl-1-butanol in an ionic liquid (IL). Effects of various reaction conditions on the synthetic activity of the enzyme as well as enantioselectivity, including the type of IL, acyl donor, temperature, water activity, and substrate molar ratio were inverstigated. APE1547 showed good catalytic performance (activity > 0.8 μmol/min/mg, E > 25), and the enzyme-IL mixture was recycled five times with only a slight decrease in catalytic performance.     

Whole‐cell biocatalytic of Bacillus cereus WZZ006 strain to synthesis of indoxacarb intermediate: (S)‐5‐Chloro‐1‐oxo‐2,3‐dihydro‐2‐hydroxy‐1H‐indene‐2‐carboxylic acid methyl ester

In this study, a newly isolated strain screened from the indoxacarb‐rich agricultural soils, Bacillus cereus WZZ006, has a high stereoselectivity to racemic substrate 5‐chloro‐1‐oxo‐2,3‐dihydro‐2‐hydroxy‐1H‐indene‐2‐carboxylic acid methyl ester. (S)‐5‐chloro‐1‐oxo‐2,3‐dihydro‐2‐hydroxy‐1H‐indene‐2‐carboxylic acid methyl ester was obtained by bio‐enzymatic resolution. After the 36‐hour hydrolysis in 50‐mM racemic substrate under the optimized reaction conditions, the e.e._s was up to 93.0% and the conversion was nearly 53.0% with the E being 35.0. Therefore, B cereus WZZ006 performed high‐level ability to produce (S)‐5‐chloro‐1‐oxo‐2,3‐dihydro‐2‐hydroxy‐1H‐indene‐2‐carboxylic acid methyl ester. This study demonstrates a new biocatalytic process route for preparing the indoxacarb chiral intermediates and provides a theoretical basis for the application of new insecticides in agricultural production.     

A comparison of the conversion of 1-amino-2-ethylcyclopropane-1-carboxylic acid stereoisomers to 1-butene by pea epicotyls and by a cell-free system

The characteristics of the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by pea (Pisum sativum L.) epicotyls and by pea epicotyl enzyme are compared. Of the four stereoisomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid (AEC), only (1R,2S)-AEC is preferentially converted to 1-butene in pea epicotyls. This conversion is inhibited by ACC, indicating that butene production from (1R,2S)-AEC and ethylene production from ACC are catalyzed by the same enzyme. Furthermore, pea epicotyls efficiently convert ACC to ethylene with a low K _m (66 M) for ACC and do not convert 4-methylthio-2-oxo-butanoic acid (KMB) to ethylene, thus demonstrating high specificity for its substrate. In contrast, the reported pea epicotyl enzyme which catalyzes the conversion of ACC to ethylene had a high K _m (389 mM) for ACC and readily converted KMB to ethylene. We show, moreover, that the pea enzyme catalyzes the conversion of AEC isomers to butene without stereodiscrimination. Because of its lack of stereospecificity, its low affinity for ACC and its utilization of KMB as a substrate, we conclude that the reported pea enzyme system is not related to the in-vivo ethylene-forming enzyme.Abbreviations ACC 1-Amino cyclopropane-1-carboxylic acid - AEC 1-amino-2-ethylcyclopropane-1-carboxylic acid - EFE ethylene-forming enzyme - KMB 4-methylthio-2-oxobutanoic acid     

Chiral superstructures from homochiral Zn2+, Co2+, Fe2+‐2,6‐bis (aryl ethylimine)pyridine complexes

We report the hierarchical supramolecular organization of metallosupramolecular homochiral complexes 1 ‐Λ‐(S,S,S,S)‐M²⁺/ 1 ‐?‐(R,R,R,R)‐M²⁺ and 2 ‐ Λ‐(S,S,S,S)‐M²⁺/ 2 ‐?‐ (R,R,R,R)‐M²⁺ of M²⁺ = Co²⁺, Fe²⁺, Zn²⁺ metal ions with chiral pseudo‐terpyridine‐type ligands: 1‐ (S,S) or 1‐ (R,R) = 2,6‐bis (naphthyl ethylimine)pyridine and 2‐ (S,S) or 2‐ (R,R) = 2,6‐bis (phenyl‐ethylimine)pyridine. Circular dichroism measurements in solution were used to confirm the enantiomeric nature of all twelve complexes. For crystal structures of 1 ‐ Λ‐ (S,S,S,S)‐M²⁺ or 1 ‐?‐ (R,R,R,R)‐M²⁺ complexes, absolute configurations {? (or P), Λ (or M)} were confirmed by refinement of the Flack parameter x: ?0.007 ≤ x ≤ 0.11 for the single crystals of 1 ‐Λ‐(S,S,S,S)‐M²⁺/ 1 ‐?‐ (R,R,R,R)‐M²⁺, 2 ‐ Λ‐ (S,S,S,S)‐Fe²⁺, and 2 ‐?‐ (R,R,R,R)‐Co²⁺.     

Synthesis of one diastereomeric couple of the mucolytic drug domiodol [(4S, 2R,S)-2-iodomethyl-4-hydroxymethyl-1,3-dioxolane] from D-mannitol as chiral starting material

The acid-catalyzed reaction of D-mannitol 4 with bromoacetaldehyde diethyl acetal followed by periodate cleavage of the corresponding diacetal 5 afforded (4S, 2R, S)-2-bromomethyl-4-hydroxymethyl-1,3-dioxolane 3c in good yields, from which the title compound 1 is obtained by displacement of the bromine with lithium iodide. © 1995 Wiley-Liss, Inc.