Optical Resolution by Preferential Crystallization of (RS)-2-Amino-3-(2-carboxyethylthio)propanoic Acid

Electrophilic additions of DL- and L-Cys to propenoic acid afforded (RS)- and (R)-2-amino-3-(2-carboxyethylthio)propanoic acids [(RS)- and (R)-ACE], respectively. (RS)-ACE was found to exist as a conglomerate based on its melting point, solubility, and infrared spectrum. (RS)-ACE was optically resolved by preferential crystallization to yield (R)- and (S)-ACE. The obtained (R)- and (S)-ACE were efficiently recrystallized from water, taking account of the solubility of (RS)-ACE, to give them in optically pure form.     

Synthesis of Optically Active 1,4-Thiazane-3-carboxylic Acid via Optical Resolution by Preferential Crystallization of (RS)-2-Amino-3-[(2-chloroethyl)sulfanyl]propanoic Acid Hydrochloride

Optically active 1,4-thiazane-3-carboxylic acid [TCA] was synthesized from cysteine via optical resolution by preferential crystallization. The intermediate (RS)-2-amino-3-[(2-chloroethyl)sulfanyl]propanoic acid hydrochlo-ride [(RS)-ACS?HCl] was found to exist as a conglomerate based on its melting point, solubility and IR spectrum. (RS)-ACS?HCl was optically resolved by preferential crystallization to yield (R)- and (S)-ACS?HCl. (R)- and (S)-ACS?HCl thus obtained were recrystallized from a mixture of hydrochloric acid and 2-propanol, taking account of the solubility of (RS)-ACS?HCl, efficiently yielding both enantiomers in optically pure forms. (R)- and (S)-TCA were then respectively synthesized by the cyclization of (R)- and (S)-ACS?HCl in ethanol in the presence of triethylamine.     

Optical resolution by preferential crystallization of (RS)-2-amino-3-chloropropanoic acid hydrochloride

The racemic structures of (RS)-2-amino-3-chloropropanoic acid [(RS)-ACP] and (RS)-2-amino-3-chloropropanoic acid hydrochloride [(RS-ACP·HCl] were examined to obtain (R)- and (S)-ACP via optical resolution by preferential crystallization. The melting point, infrared spectrum, solubility, and ternary solubility diagram suggested that (RS)-ACP·HCl exists as a conglomerate and that (RS)-ACP forms a racemic compound. Optical resolution by preferential crystallization of (RS)-ACP·HCl was successfully achieved to yield (R)- and (S)-ACP·HCl. Optically pure (R)- and (S)-ACP were obtained from the purified (R)-and (S)-ACP·HCl, respectively. © 1996 Wiley-Liss, Inc.     

Preparation and isolation of 2-methylamino-3-phenylpropanoic acid enantiomers using selective crystallization

First, (RS)-2-chloro-3-phenylpropanoic acid [(RS)-CPP] was optically resolved using ethyl (S)-phenylalaninate as a resolving agent, aiming at preparation of optically active 2-methylamino-3-phenylpropanoic acid (MPP). The (R)-CPP obtained as the sodium salt monohydrate was reacted with methylamine to give (S)-2-methylamino-3-phenylpropanoic acid [(S)-MPP]. Next, the optical resolution of (RS)-MPP was also attempted via molecular compound formation with optically active mandelic acid (MAN). The molecular compound of (R)-MPP with (S)-MAN [(R)-MPP (S)-MAN] was obtained as the less soluble diastereomeric compound, while the (S)-MPP (S)-MAN compound was found to be the more soluble one. Recrystallization of (R)-MPP (S)-MAN compound from water, followed by treatment with acetone, gave optically pure (R)-MPP in 79% yield, based on a half amount of the starting (RS)-MPP. The (S)-MPP obtained from (S)-MPP (S)-MAN compound was again subjected to formation of molecular compound with (R)-MAN to give optically pure (S,)-MPP in 66% yield. Chirality 9:386–389, 1997. © 1997 Wiley-Liss, Inc.     

Preparation of Optically Active 2-Aminobutanoic Acid via Optical Resolution by Replacing Crystallization

An attempt was made to use a simple procedure to obtain (R)- and (S)-2-aminobutanoic acids [(R)- and (S)-1] which are non-proteinogenic α-amino acids and are useful as chiral reagents in asymmetric syntheses. Compound (RS)-1 p-toluenesulfonate [(RS)-2], which is known to exist as a conglomerate, was optically resolved by replacing crystallization with (R)- and (S)-methionine p-toluenesulfonate [(R)- and (S)-3] as optically active co-solutes. When (S)-3 was employed as the co-solute, (R)-2 was preferentially crystallized from a supersaturated solution of (RS)-2 in 1-propanol, as was (S)-2 in the presence of (R)-3. (R)- and (S)-2 recrystallized from 1-propanol were treated with triethylamine in methanol to give (R)- and (S)-1 in optically pure forms.     

Inheritance of evolved glyphosate resistance in <Emphasis Type="Italic">Conyza canadensis</Emphasis> (L.) Cronq.

N-(phosphonomethyl)glycine (glyphosate) resistance was previously reported in a horseweed [Conyza (=Erigeron) canadensis (L.) Cronq.] population from Houston, DE (P ₀ ^R ). Recurrent selection was performed on P ₀ ^R , since the population was composed of susceptible (5%) and resistant (95%) phenotypes. After two cycles of selection at 2.0 kg ae glyphosate ha^–1, similar glyphosate rates that reduced plant growth by 50%, glyphosate rates that inflicted 50% mortality in the population, and accumulations of half of the maximum detectable shikimic acid concentration were observed between the parental P ₀ ^R and the first (RS₁) and second (RS₂) recurrent generations. In addition, RS₁ and RS₂ did not segregate for resistance to glyphosate. This suggested that the RS₂ population comprised a near-homozygous, glyphosate-resistant line. Whole-plant rate responses estimated a fourfold resistance increase to glyphosate between RS₂ and either a pristine Ames, IA (P ₀ ^P ) or a susceptible C. canadensis population from Georgetown, DE (P ₀ ^S ). The genetics of glyphosate resistance in C. canadensis was investigated by performing reciprocal crosses between RS₂ and either the P ₀ ^P or P ₀ ^S populations. Evaluations of the first (F₁) and second (F₂) filial generations suggested that glyphosate resistance was governed by an incompletely dominant, single-locus gene (R allele) located in the nuclear genome. The proposed genetic model was confirmed by back-crosses of the F₁ to plants that arose from achenes of the original RS₂, P ₀ ^P , or P ₀ ^S parents. The autogamous nature of C. canadensis, the simple inheritance model of glyphosate resistance, and the fact that heterozygous genotypes (F₁) survived glyphosate rates well above those recommended by the manufacturer, predicted a rapid increase in frequency of the R allele under continuous glyphosate selection. The impact of genetics on C. canadensis resistance management is discussed.     

Synthesis and nootropic activity of some 2,3-dihydro-1H-isoindol-1-one derivatives structurally related with piracetam

Three 2,3‐dihydro‐1H‐isoindol‐1‐ones structurally related with piracetam (=2‐oxopyrrolidine‐1‐acetamide) have been synthesized and tested for their nootropic effects in the passive avoidance test in mice. Compounds (RS)‐ 2 , (R,R)‐ 3 , and (R,S)‐ 3 were obtained in good yields in only two steps starting from methyl dl ‐phthaloylalanine. Compound (RS)‐ 2 exhibited nootropic activity at lower doses than piracetam, used as reference drug, but it showed lower efficacy. Whereas diastereoisomers (R,R)‐ 3 and (R,S)‐ 3 were as potent as piracetam to revert amnesia induced by scopolamine, (R,S)‐ 3 showed lower efficacy than (R,R)‐ 3 . Only (R,R)‐ 3 showed myorelaxant effect at doses of 10 and 30 mg/kg; other compounds did not exhibit any anticonvulsant, sedative, myorelaxant, or impaired motor‐coordination effect in mice. These synthesized 2,3‐dihydro‐1H‐isoindol‐1‐one derivatives constitute a new kind of nootropic compounds.     

Synthesis of Both the Enantiomers of 3-Octanol,the Pheromone of Various Species of Ants

(2S,3R,1′S,2′S)-Serricorole (1) and (2S,3R,1′R)-serricorone (2), sex pheromone components of the cigarette beetle (Lasioderma serricorne F.), were synthesized, starting from the enantiomers of methyl 3-hydroxypentanoate. The stereochemistry of the naturally occurring 1 was determined to be 2S,3R,1′S,2′S, and that of 2 to be 2S,3R,1′RS by comparing between the CD spectra of the natural and synthetic samples.     

Effect of chiral enhancers on the permeability of optically active and racemic metoprolol across hairless mouse skin

The stratum corneum, the rate‐limiting barrier in transdermal drug delivery, is chiral in nature and enantiomers behave differently with respect to their transport across the skin, resulting in enantioselective permeation. The permeation characteristics of individual enantiomers of metoprolol free base (MB) were investigated using hairless mouse skin. The influence of chiral permeation enhancers, l‐menthol and (±)‐linalool, on the permeation of MB was also investigated. In the absence of enhancers, the permeation profiles of R‐ and S‐MB from donor solutions containing either RS‐MB or pure enantiomers are comparable (p < 0.05). In presence of enhancers, l‐menthol and (±)‐linalool, the flux values were increased 2.4‐ to 3.0‐fold, respectively, and the permeation profiles of R‐ and S‐MB from donor solutions containing RS‐MB are comparable (p < 0.05). However, when donor vehicle contains pure enantiomers, the permeation enhancing effect of l‐menthol on S‐MB was significantly higher (by 25%) than on R‐MB (p < 0.05). Further, in presence of l‐menthol, the flux of S‐MB from donor solution containing pure S‐MB was 35% higher than the flux of RS‐MB from racemate. No such effect was seen with (±)‐linalool. In all the investigations, no enantiomeric inversion was observed during the permeation process. The lag times were shorter in the case of l‐menthol compared with (±)‐linalool. Chirality 11:536–540, 1999. © 1999 Wiley‐Liss, Inc.     

Purification and characterization of an alcohol dehydrogenase from 1,2-propanediol-grownDesulfovibrio strain HDv

The sulfate-reducing bacterimDesulfovibrio strain HDv (DSM 6830) grew faster on (S)- and on (R, S)-1,2-propanediol (μ_max 0.053 h⁻) than on (R)-propanediol (0.017 h⁻¹) and ethanol (0.027 h⁻¹). From (R, S)-1,2-propanediol-grown cells, an alcohol dehydrogenase was purified. The enzyme was oxygen-labile, NAD-dependent, and decameric; the subunit mol. mass was 48 kDa. The N-terminal amino acid sequence indicated similarity to alcohol dehydrogenases belonging to family III of NAD-dependent alcohol dehydrogenases, the first 21 N-terminal amino acids being identical to those of theDesulfovibrio gigas alcohol dehydrogenase. Best substrates were ethanol and propanol (K _m of 0.48 and 0.33 mM, respectively). (R, S)-1,2-Propanediol was a relatively poor substrate for the enzyme, but activities in cell extracts were high enough to account for the growth rate. The enzyme showed a preference for (S)-1,2-propanediol over (R)-1,2-propanediol. Antibodies raised against the alcohol dehydrogenase ofD. gigas showed cross-reactivity with the alcohol dehydrogenase ofDesulfovibrio strain HDv and with cell extracts of six other ethanol-grown sulfate-reducing bacteria.     

Production of (R)-3-pentyn-2-ol through stereoinversion of racemic 3-pentyn-2-ol by Nocardia fusca AKU 2123

Wet cells of Nocardia fusca AKU 2123 are good catalysts for the production of (R)-3-pentyn-2-ol (PYOH) from (RS)-PYOH through a stereoinversion reaction. Under optimal conditions (350 mM potassium phosphate buffer, pH 8.0, 30% (w/v) wet cells, 0.12% NADPH, 10% glucose, and 30 U/ml glucose dehydrogenase) (R)-PYOH of high optical purity (98.7% e.e.) was produced from 2% (v/v) (RS)-PYOH with a yield of 70.4% by 140 h incubation. Received: 22 January 1999 / Received revision: 23 April 1999 / Accepted: 1 May 1999     

Effect of temperature upon catalytic properties of lactate dehydrogenase in the lobster

Lactate dehydrogenase (LDH) present in the tail muscle of the lobster (H. vulgaris) exhibits substrate (pyruvate and L-lactate) inhibition which is temperature-dependent. Such inhibitions can be related to the formation of stable LDH-NAD ⁺-pyruvate and LDH-NADH-lactate complexes. The apparent K_m of pyruvate and L-lactate increase when the temperature rises above 12°. These temperature-dependent kinetic properties may play a major role in determining the metabolic fate of pyruvate.     

Reduction of N-oxides and sulfoxide by the same terminal reductase inProteus mirabilis

Proteus mirabilis can grow anaerobically on the fermentable substrate, glucose. When the glucose medium was supplemented with an electron acceptor, growth doubled. However, the organism failed to grow anaerobically on the oxidizable substrate glycerol unless the medium was supplemented with an external electron acceptor. Dimethyl sulfoxide (DMSO), trimethylamine N-oxide (TMAO), nicotinamide N-oxide (NAMO), and nitrate (NO₃) can serve this function. Cell-free extracts ofP. mirabilis can reduce these compounds in the presence of various electron donors. In order to determine whether the same or different terminal reductase(s) are involved in the reduction of these compounds, we isolated mutants unable to grow on glycerol/DMSO medium. When these mutants were tested on glycerol medium containing TMAO, NAMO, and NO₃ as electron acceptors, it was found that there were two groups. Group I mutants were unable to grow with DMSO, TMAO, and NAMO, while their growth was unaffected with NO₃. Group II mutants were unable to grow on any electron acceptor including NO₃. Enzyme assays using reduced benzyl viologen with both groups of mutants were in agreement with growth studies. On the basis of these results, we conclude that the same terminal reductase is involved in the reduction of DMSO, TMAO, and NAMO (group I) and that the additional loss of NO₃ reductase in group II mutants is probably owing to a defect in the synthesis or insertion of molybdenum cofactor.     

Stereoselective Synthesis of erythro-Serricornin, (4R, 6R, 7S)-, and (4S, 6R, 7S)-4,6-Dimethyl-7-hydroxynonan-3-one,Stereoisomers of the Sex Pheromone of Cigarette Beetle

A stereoselective synthesis of erythro-serricornin [(4RS,6R,7S)-4,6-dimethyl-7-hydroxynonan-3-one] was completed starting from l-(+)-tartaric acid. The relative configuration of C(6)-methyl and C(7)-hydroxyl groups in naturally occurring serricornin was threo.     

CALB-catalyzed kinetic resolution of (RS)-3-benzoylthio-2-methylpropyl azolides: kinetic and thermodynamic analysis

Abstract

Zofenopril as an ACE inhibitor expired recently was found to have a favourable safety profile in comparison with other ACE inhibitors in treating high blood pressure, congestive heart failure, and acute myocardial infarction. It can be synthesised from the key building blocks of (S)-3-benzoylthio-2-methylpropanoic acid and (4S)-phenylthio-L-proline. In this report, an efficient hydrolytic resolution via Candida antarctic lipase B (CALB) for preparing the former block in isopropyl ether (IPE) containing (RS)-3-benzoylthio-2-methylpropyl pyrazolide (1) and water was developed. Quantitative improvements of the enzyme activity and enantioselectivity in terms of k_2SK_mS^?1?=?5.726?L h^?1 g^?1 and E?=?217 at 45?°C were found from the kinetic analysis. Insights into the CALB performance via thermodynamic analysis were then addressed and compared with those by using (RS)-3-benzoylthio-2-methylpropyl 1,2,4-triazolide (2) as the substrate. A putative thermodynamic model was moreover hypothesised for elucidating the more enthalpy reduction of 68.92-70.86?kJ mol^?1 from the acyl part of (S)-1 and (S)-2 as well as that of 23.69-25.63?kJ mol^?1 from the triad imidazolium to Ser105 and leaving 1,2,4-triazole moiety of (R)-2 and (S)-2 on stabilising the corresponding transition states.     

Growth and condition of juvenile coho salmon Oncorhynchus kisutch relate positively to species richness of trophically transmitted parasites

The aims of this study were first, to test the hypothesis that metrics of fish growth and condition relate positively to parasite species richness (S_R) in a salmonid host; second, to identify whether S_R differs as a function of host origin; third, to identify whether acquisition of parasites through marine v. freshwater trophic interactions was related to growth and condition of juvenile salmonids. To evaluate these questions, species diversity of trophically transmitted parasites in juvenile coho salmon Oncorhynchus kisutch collected off the coast of the Oregon and Washington states, U.S.A. in June 2002 and 2004 were analysed. Fish infected with three or more parasite species scored highest in metrics of growth and condition. Fish originating from the Columbia River basin had lower S_R than those from the Oregon coast, Washington coast and Puget Sound, WA. Parasites obtained through freshwater or marine trophic interactions were equally important in the relationship between S_R and ocean growth and condition of juvenile O. kisutch salmon.     

Racemization of the aqua-{N-salicylidene-(S)-alaninato}copper(II) by reaction with potassium cyanate

Copper(II) N-salicylidene-(S)-alaninate trihydrate reacting as the S-enantiomeric parent compound with KOCN in hot diluted methanol yielded by slow crystallisation from the cooled reaction mixture (in the course of 1 day) the racemic product K[Cu{sal-(RS)-ala}(NCO)]. The parameters of the axial type EPR spectrum in X-band region and the LF band position in the electronic spectrum are typical of an axially distorted square pyramidal coordination of the Cu(II) atom in this complex. The spectral properties of the complex cuprate prepared and its basal crystallographic data are consistent with those of the earlier studied¹⁵ K₂[Cu₂{sal-(RS)-ala}₂(μ-NCO)₂] synthetized by using [Cu{sal-(RS)-ala}(H₂O)].H₂O as the racemic parent complex in the reaction mixture with KOCN.     

Neopeptins A and B,New Antifungal Antibiotics

An enzyme that reduces benzoylformate with NADH to form (R)-mandelate was extracted from cells of Streptococcus faecalis IFO 12964 and purified to more than 95% purity as evidenced by gel electrophoresis. Physicochemical and enzymic properties were studied. From the substrate specificity, we concluded that the enzyme was a kind of (R)-2-hydroxyisocaproate dehydrogenase. Optically pure (R)-(—)-mandelic acid was prepared with the enzyme, NADH, and alcohol, formate or glucose dehydrogenase in 84~93% yield. Five (R)-2-hydroxyalkanoic acids (C₄~C₆) or their Ba salts, (R)-(+)-3-phenyllactic acid and (S)-(—)-3-chlorolactic acid were also prepared with the enzyme.     

Phosphate-limited growth of Chromatium vinosum in continuous culture

Chromatium vinosum DSM 185 was grown in continuous culture at a constant dilution rate of 0.071 h^-1 with sulfide as the only electron donor. The organism was subjected to conditions ranging from phosphate limitation (S _R-phosphate=2.7 M and S _R-sulfide=1.8 mM) to sulfide limitation (S _R-phosphate=86 M and S _R-sulfide=1.8 mM). At values of S _R-phosphate below 7.5 M the culture was washed out, whereas S _R-phosphate above this value resulted in steady states. The saturation constant (K ) for growth on phosphate was estimated to be between 2.6 and 4.1 M. The specific phosphorus content of the cells increased from 0.30 to 0.85 mol P mg^-1 protein with increasing S _R-phosphate. The specific rate of phosphate uptake increased with increasing S _R-phosphate, and displayed a non-hyperbolic saturation relationship with respect to the concentration of phosphate in the inflowing medium. Approximation of a hyperbolic saturation function yielded a maximum uptake rate (V _max) of 85 nmol P mg^-1 protein h^-1, and a saturation constant for uptake (K _t) of 0.7 M. When phosphate was supplied in excess 8.5% of the phosphate taken up by the cells was excreted as organic phosphorus at a specific rate of 8 nmol P mg^-1 protein h^-1.Non-standard abbreviations BChla bacteriochlorophyll a - D dilution rate; _max, maximum specific growth rate - maximum specific growth rate if the substrate were not inhibitory - K saturation constant for growth on phosphate - V _max maximum rate of phosphate uptake - K _i saturation constant for phosphate uptake - K _i inhibition constant for growth in the presence of sulfide - S _R concentration of substrate in the inflowing medium     

Enantioselective Uptake and Degradation of the Chiral Herbicide Dichlorprop [(RS)-2-(2,4-Dichlorophenoxy)propanoic acid] by Sphingomonas herbicidovorans MH

Sphingomonas herbicidovorans MH was able to completely degrade both enantiomers of the chiral herbicide dichlorprop [(RS)-2-(2,4-dichlorophenoxy)propanoic acid], with preferential degradation of the (S) enantiomer over the (R) enantiomer. These results are in agreement with the recently reported enantioselective degradation of mecoprop [(RS)-2-(4-chloro-2-methylphenoxy)propanoic acid] by this bacterium (C. Zipper, K. Nickel, W. Angst, and H.-P. E. Kohler, Appl. Environ. Microbiol. 62:4318–4322, 1996). Uptake of (R)-dichlorprop, (S)-dichlorprop, and 2,4-D (2,4-dichlorophenoxyacetic acid) was inducible. Initial uptake rates of cells grown on the respective substrate showed substrate saturation kinetics with apparent affinity constants (K_t) of 108, 93, and 117 μM and maximal velocities (V_max) of 19, 10, and 21 nmol min⁻¹ mg of protein⁻¹ for (R)-dichlorprop, (S)-dichlorprop, and 2,4-D, respectively. Transport of (R)-dichlorprop, (S)-dichlorprop, and 2,4-D was completely inhibited by various uncouplers and by nigericin but was only marginally inhibited by valinomycin and by the ATPase inhibitor N,N′-dicyclohexylcarbodiimine. Experiments on the substrate specificity of the putative transport systems revealed that (R)-dichlorprop uptake was inhibited by (R)-mecoprop but not by (S)-mecoprop, (S)-dichlorprop, or 2,4-D. On the other hand, the (S)-dichlorprop transport was inhibited by (S)-mecoprop but not by (R)-mecoprop, (R)-dichlorprop, or 2,4-D. These results provide evidence that the first step in the degradation of dichlorprop, mecoprop, and 2,4-D by S. herbicidovorans is active transport and that three inducible, proton gradient-driven uptake systems exist: one for (R)-dichlorprop and (R)-mecoprop, another for (S)-dichlorprop and (S)-mecoprop, and a third for 2,4-D.