Biomimetic synthesis of acid-sensitive (-)- and (+)-caparrapi oxides, (-)- and (+)-8-epicaparrapi oxides, and (+)-dysifragin induced by artificial cyclases

Asymmetric total syntheses of acid-sensitive (-)- and (+)-caparrapi oxides (1) and (+)-8-epicaparrapi oxide (2) from farnesol (10) are achieved using Sharpless-Katsuki epoxidation and Lewis acid-assisted chiral Br?nsted acid (chiral LBA)-induced polyene cyclization as key steps. The relative configuration of (+)-dysifragin (4) is determined by a single-crystal X-ray diffraction and its total synthesis is accomplished by the diastereoselective epoxidation of (+)-1. Furthermore, (-)-1 can be directly synthesized from (S)-nerolidol (3) and (R)-LBA with 88% ds by reagent control, which overcame substrate control, while (-)-2 is obtained from (R)-3 and (R)-LBA with >99% ds by the double asymmetric induction.     

Cation selective electroanalysis of K(+)-, Na(+)- and Ca2(+) concentrations in acetate dialysis solutions

An account is given on the influence of acetate ions in direct potentiometric analyses of dialytic solutions using K+, Na+ and Ca2+ selective carrier PVC solid contact sensors. By calibrating the flow-through membrane electrodes with anion-corrected solutions, the deviation of ion concentrations based on the acetate effect can be eliminated. The phenomena observed are attributed primarily to an acetate anion interference.     

(+)-7-Iso-jasmonic acid and related compounds from botryodiplodia theobromae

Metabolites produced by Botryodiplodia theobromae (synonym Lasiodiplodia theobromae) possessing plant growth regulating activities were shown to be the 7-epimer of jasmonic acid and its derivatives.     

First chemoenzymatic synthesis of (+)-2-carboxypyrrolidine-3-acetic acid, the nucleus of kainoid amino acids

The distinctive nucleus of kainoid amino acids, (2S,3R)-(+)-2-carboxypyrrolidine-3-acetic acid 6, was synthesized by a chemoenzymatic process, exploiting the diastereomeric cis/trans methyl pyroglutamate derivatives 10a-c/11a-c as key intermediates. These mixtures, when subjected to a kinetic resolution mediated by α-chymotrypsin, reacted diastereo-, regio-, and enantioselectively to give the trans derivatives (+)-10a-c possessing the correct (2S,3R) configuration. Subsequently, the desired product (2S,3R)-(+)-6 could be obtained after well-established transformations.     

Inactivation of Ca2(+)-, Na+K(+)-, and H+K(+)-ATPases with a carbodiimide derivative of ATP

The gamma-P adduct of ATP with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (ATP-EDC) was synthesized and incubated with the Ca-ATPase of sarcoplasmic reticulum with the result that time-dependent complete loss of the enzyme's activity occurred. The inactivation required calcium and magnesium while ATP had a protective effect. ATP-EDC incubation with the NaK-ATPase and HK-ATPase produced partial (greater than 50%) inactivation, but had no effect on myosin S1, pyruvate kinase and hexokinase, suggesting that this ATP analog is a specific inactivator of the so-called 'P-type' ATPases.     

(+)-(S)-trujillon, (+)-(S)-4-(2,2-diphenyl-1,3,2-oxazabolidin-5-oxo)propionic acid, a novel glutamatergic analog, modifies the activity of globus pallidus neurons by selective NMDA receptor activation

Decreased levels of glutamate and changes in several markers of glutamatergic function occur in movement disorders and chronic psychiatric illnesses. Ionotropic glutamate receptors have been implicated in neuronal cell death, and have, therefore, been related to the process of neurodegenerative diseases. Drugs that interact with the glutamatergic system are important tools for the development of better therapies. We examined the effect of a new glutamatergic analog, (+)-(S)-4-(2,2-diphenyl-1,3,2-oxazabolidin-5-oxo)propionic acid, (+)-(S)-Trujillon, on the spontaneous globus pallidus neuronal activity of the anesthetized rat. (+)-(S)-Trujillon excited most pallidal neurons in a dose-dependent manner. Furthermore, blockade of NMDA receptors (NMDARs) inhibited the (+)-(S)-Trujillon-induced excitation, whereas blockade of AMPA/kainate receptors did not. In addition, computational docking studies showed micromolar-range affinities of (+)-(S)-Trujillon for NR2A NMDARs. Our results indicate that (+)-(S)-Trujillon selectively activates NMDARs, an effect that could prove to be a useful tool in the analysis of motor, behavioral, and cognitive disorders, where NMDAR-mediated signaling is altered.     

Phosphorylation of the salivary Na(+)-K(+)-2Cl(-) cotransporter

Westudied the phosphorylation of the secretoryNa⁺-K⁺-2Cl cotransporter (NKCC1)in rat parotid acinar cells. We have previously shown that NKCC1activity in these cells is dramatically upregulated in response to-adrenergic stimulation and that this upregulation correlates withNKCC1 phosphorylation, possibly due to protein kinase A (PKA). We showhere that when ATP is added to purified acinar basolateral membranes(BLM), NKCC1 is phosphorylated as a result of membrane-associatedprotein kinase activity. Additional NKCC1 phosphorylation is seen whenPKA is added to BLMs, but our data indicate that this is due to aneffect of PKA on endogenous membrane kinase or phosphatase activities,rather than its direct phosphorylation of NKCC1. Also, phosphopeptidemapping demonstrates that these phosphorylations do not take place atthe site associated with the upregulation of NKCC1 by -adrenergicstimulation. However, this upregulatory phosphorylation can be mimickedby the addition of cAMP to permeabilized acini, and this effect can beblocked by a specific PKA inhibitor. These latter results provide good evidence that PKA is indeed involved in the upregulatoryphosphorylation of NKCC1 and suggest that an additional factor presentin the acinar cell but absent from isolated membranes is required to bring about the phosphorylation.

     

Synthesis of (R)-(+)-hippospongic acid A, a triterpene isolated from the marine sponge, Hippospongia sp.

Hippospongic acid A (1) is a triterpene metabolite of the marine sponge, Hippospongia sp., with inhibitory activity against the gastrulation of starfish embryos. (R)-(+)-1 was synthesized by employing enzymatic kinetic resolution as the key step.     

Isolation and identification of S(+)-3-hydroxyisobutyric acid in the urine of rats loaded with isobutyric acid.

3-Hydroxyisobutyric acid has been isolated from the urine of rats loaded with sodium isobutyrate. An optical rotation measurement of the methyl ester derivative shows this compound to be the S(+) stereoisomer. This is the same stereoisomer that has been previously identified in cultures of bacteria incubated with ammonium isobutyrate (Aberhart, D.J. (1977) Bioorg. Chem. 6, 191--201).     

Kinetics of maize leaf elongation IV. Effects of (+)- and (-)-abscisic acid

Abscisic acid (ABA) is involved in many of the responses of plants to environmental stress. This study focuses on the inhibitory effect of ABA on leaf expansion. In addition, the effects of (+)-ABA, the natural form of ABA, were compared to the effects of (-)-ABA. Leaf elongation rates (LER) were measured for the 3rd leaf of maize plants. ABA concentrations were measured by RIA for total ABA and an ELISA specific for (+)-ABA. ABA was added to the hydroponic solution and changes in the LER were measured over time. ABA could inhibit LER within 30 min ad reached steady-state LER within 4 h. Internal ABA concentrations in the growing zone of the leaf also reached steady-state concentrations after 4 h. This effect of ABA was reversible, because LER was fully restored upon removal of externally applied ABA, and internal concentrations of ABA in the growing zone returned to normal levels, whereas ABA concentrations remained elevated in mature tissue. Thus, steady-state LER was highly correlated with the steady-state internal ABA concentration of the growing zone. ABA inhibited leaf expansion by increasing the apparent cell wall yield threshold; no other growth parameters were affected. The (-)-enantiomer of ABA had much less effect on LER than (+)-ABA when compared upon an external concentration basis. Internal ABA concentrations rationalized the response, showing that (-)-ABA accumulation was very low, most likely due to low uptake rates. From this analysis, it was determined that LER was equally sensitive to internal concentrations of (+)- or (-)-ABA.     

(+)-Isorangiformic acid,a lichen substance from Lecanora stenotropa

(+)-Isorangiformic acid from the lichen Lecanora stenotropa has been shown to be (+)-2S-methoxycarbonyl-3S-heptadecanedicarboxylic acid.     

Biosynthesis of monoterpenes. Enantioselectivity in the enzymatic cyclization of (+)- and (-)-linalyl pyrophosphate to (+)- and (-)-pinene and (+)- and (-)-camphene

Cyclase I from Salvia officinalis leaf catalyzes the conversion of geranyl pyrophosphate to the stereo-chemically related bicyclic monoterpenes (+)-alpha-pinene and (+)-camphene and to lesser quantities of monocyclic and acyclic olefins, whereas cyclase II from this plant tissue converts the same acyclic precursor to (-)-alpha-pinene, (-)-beta-pinene and (-)-camphene as well as to lesser amounts of monocyclics and acyclics. These antipodal cyclizations are considered to proceed by the initial isomerization of the substrate to the respective bound tertiary allylic intermediates (-)-(3R)- and (+)-(3S)-linalyl pyrophosphate. [(3R)-8,9-14C,(3RS)-1E-3H]Linalyl pyrophosphate (3H:14C = 5.14) was tested as a substrate with both cyclases to determine the configuration of the cyclizing intermediate. This substrate with cyclase I yielded alpha-pinene and camphene with 3H:14C ratios of 3.1 and 4.2, respectively, indicating preferential, but not exclusive, utilization of the (3R)-enantiomer. With cyclase II, the doubly labeled substrate gave bicyclic olefins with 3H:14C ratios of from 13 to 20, indicating preferential, but not exclusive, utilization of the (3S)-enantiomer in this case. (3R)- and (3S)-[1Z-3H]linalyl pyrophosphate were separately compared to the achiral precursors [1-3H]geranyl pyrophosphate and [1-3H]neryl pyrophosphate (cis-isomer) as substrates for the cyclizations. With cyclase I, geranyl, neryl, and (3R)-linalyl pyrophosphate gave rise exclusively to (+)-alpha-pinene and (+)-camphene, whereas (3S)-linayl pyrophosphate produced, at relatively low rates, the (-)-isomers. With cyclase II, geranyl, neryl, and (3S)-linalyl pyrophosphate yielded exclusively the (-)-isomer series, whereas (3R)-linalyl pyrophosphate afforded the (+)-isomers at low rates. These results are entirely consistent with the predicted stereochemistries and additionally revealed the unusual ability of these enzymes to catalyze antipodal cyclizations when presented with the unnatural linalyl enantiomer.     

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.     

In vitro inhibitory effect of gossypol from gossypol-acetic acid, and (+)- and (-)-isomers of gossypol on the growth of Edwardsiella ictaluri

AIM: This study was conducted to evaluate the toxic effect of gossypol from gossypol-acetic acid, and (+)- and (-)-isomers of gossypol on the growth of Edwardsiella ictaluri. METHODS AND RESULTS: Inhibitory effect of various concentrations of gossypol on the growth of E. ictaluri was determined. Bacterial recovery was performed by preincubation of bacteria in medium containing various concentrations of gossypol and subsequent activation of bacteria by inoculating on gossypol-free plates. Concentrations of racemic gossypol, (+)-gossypol and (-)-gossypol of 1.5 microg ml(-1) or higher significantly reduced the number of bacterial colonies compared with that of the control. The growth of E. ictaluri was completely inhibited on agar plates supplemented with 3 microg ml(-1), regardless of the forms of gossypol. The inhibitory effect of (+)-gossypol was higher than that of (-)-gossypol or gossypol-acetic acid. Recovery of E. ictaluri was <50% for all three forms of gossypol at concentrations of 5 microg ml(-1). Bacterial recovery remained relatively constant (6.5%) at gossypol concentrations from 10 to 100 microg ml(-1). Complete killing of E. ictaluri was not reached at gossypol levels up to 100 microg ml(-1). CONCLUSION: Gossypol-acetic acid, and (+)- and (-)-optical isomers have anti-bacterial effect against E. ictaluri. The results suggest the action is bacteriostatic rather than bactericidal. SIGNIFICANCE AND IMPACT OF THE STUDY: The therapeutic effect of gossypol against E. ictaluri may be useful in controlling enteric septicaemia of catfish.     

Microbial production of (+)-trans-isochorismic acid

Two methods are described for the preparation of enantiomerically pure (+)-trans-isochorismic acid, an important metabolite of the postchorismate pathway. Both methods can be employed to prepare isotopically labeled isochorismic acid. One of the two methods is suitable to prepare bulk quantities of isochorismic acid using a recombinant strain of Klebsiella pneumoniae 62-1. (c) 1995 John Wiley & Sons, Inc.