Potential of some yeast strains in the stereoselective synthesis of (R)-(−)-phenylacetylcarbinol and (S)-(+)-phenylacetylcarbinol and their reduced 1,2-dialcohol derivatives

Whole cells of different yeast species have been widely used for a number of asymmetric transformations. In the present study, the screening of several yeast strains revealed the utility of Debaryomyces etchellsii in acyloin condensation for (R)-(?)-phenylacetylcarbinol production. Some conditions for the efficient biotransformation of benzaldehyde and minimization in the production of by-products were explored: pH of the reaction medium, use of additives (ethanol or acetonitrile), temperature, time, and substrate concentration and dosing. The optimal conditions found allowed the transformation of up to 10 g/L of the starting material in reactions carried out at high scale. Furthermore, the yeast Kluyveromyces marxianus was seen to be a convenient biocatalyst to carry out the kinetic resolution by the bioreduction of racemic (+/?)-phenylacetylcarbinol, resulting in (S)-(+)-phenylacetylcarbinol with excellent stereoselectivity. Finally, the ketone reduction of both isolated stereoisomers (R and S) by D. etchellsii allowed the obtainment of two of the four diastereoisomers of 1-phenyl-1,2-propanediol. All these compounds are key precursors for the production of interesting pharmaceutical and chemical products.     

Highly selective biotransformation of (+)-(1S)- and (−)-(1R)-camphorquinone by Aspergillus wentii

Abstract

To clarify the structures of biotransformation products and metabolic pathways, the biotransformation of monoterpenoids, (+)- and (?)-camphorquinone (1a and b), has been investigated using Aspergillus wentii as a biocatalyst. Compound 1a was converted to (?)-(2S)-exo-hydroxycamphor (2a), (?)-(2S)-endo-hydroxycamphor (3a), (?)-(3S)-exo-hydroxycamphor (4a), (?)-(3S)-endo-hydroxycamphor (5a), and (+)-camphoric acid (6a). Compound 1b was converted to (+)-(2R)-exo-hydroxycamphor (2b), (+)-(2R)-endo-hydroxycamphor (3b), (+)-(3R)-exo-hydroxycamphor (4b), (+)-(3R)-endo-hydroxycamphor (5b), and (?)-camphoric acid (6b). Compound 1a mainly produced 2a (65.0%) with stereoselectivity, whereas 1b afforded 3b (84.3%) with high stereoselectivity. These structures were confirmed by gas chromatography–mass spectrometry, infrared, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR spectral data. The products illustrate the marked ability of A. wentii for enzymatic oxidation and ketone reduction.     

Determination of ((R)-(+)- and (S)-(−)-isomers of thiopentone in plasma by chiral high-performance liquid chromatography

A method for the determination of (R)-(+)- and (S)-(−)-isomers of thiopentone in plasma was developed. Following liquid-liquid extraction, the separation of enantiomers of thiopentone and the internal standard (racemic ketamine) was achieved by high-performance liquid chromatography on an α₁-acid glycoprotein (AGP) column with ultraviolet detection at 280 nm. The mobile phase consisted of 20 mM KH₂PO₄ buffer-propanol-methanol (93.5:5.0:1.5) at pH 5.0. The flow-rate was 0.9 ml/min. The limit of quantification for earch isomer was approximately 10 ng/ml. The assay is suitable for pharmacokinetic studies of (R)-(+)- and (S)-(−)-isomers of thiopentone, following usual bolus intravenous clinical doses of the racemic drug.     

Anti-viral activity of (−)- and (+)-usnic acids and their derivatives against influenza virus A(H1N1)2009

Influenza is a widespread respiratory infection. Every year it causes epidemics, quickly spreading from country to country, or even pandemics, involving a significant part of the human population of the earth. Being a highly variable infection, influenza easy accumulates the resistance mutations to many antivirals.Usnic acid, a dibenzofuran originally isolated from lichens belongs to the secondary metabolites and has a broad spectrum of biological activity. In humans, it can act as an anti-inflammatory, antimitotic, antineoplasic, antibacterial, and antimycotic agent. In this work we studied for the first time the antiviral activity of usnic acid and its derivatives against the pandemic influenza virus A(H1N1)pdm09. A total of 26 compounds representing (+) and (?) isomers of usnic acid and their derivates were tested for cytotoxicity and anti-viral activity in MDCK cells by microtetrazolium test and virus yield assay, respectively. Based on the results obtained, 50% cytotoxic dose (CTD₅₀) and 50% effective dose (ED₅₀) and selectivity index (SI) were calculated for each compound. Eleven of them were found to have SI higher than 10 (highest value 37.3). Absolute configuration was shown to have critical significance for the anti-viral activity. With minor exceptions, in the pair of enantiomers, (?)-usnic acid was more active comparing to (+)-isomer, but its biological activity was reversed after the usnic acid was chemically modified. Based on the obtained results, derivatives of usnic acid should be considered as prospective compounds for further optimization as anti-influenza substances.     

Synthesis and comparison of antiplasmodial activity of (+), (−) and racemic 7-chloro-4-(N-lupinyl)aminoquinoline

Recently the N-(?)-lupinyl-derivative of 7-chloro-4-aminoquinoline ((?)-AM-1; 7-chloro-4-{N-[(1S,9aR)(octahydro-2H-quinolizin-1-yl)methyl]amino}quinoline) showed potent in vitro and in vivo activity against both Chloroquine susceptible and resistant strains of Plasmodium falciparum. However, (?)-AM-1 is synthesized starting from (?)-lupinine, an expensive alkaloid isolated from Lupinus luteus whose worldwide production is not sufficient, at present, for large market purposes. To overcome this issue, the corresponding racemic compound, derived from synthetic (±)-lupinine was considered a cheaper alternative for the development of a novel antimalarial agent. Therefore, the racemic and the 7-chloro-4-(N-(+)-lupinyl)aminoquinoline ((±)-AM-1; (+)-AM-1) were synthesized and their in vitro antimalarial activity and cytotoxicity compared with those of (?)-AM-1. The (+)-lupinine required for the synthesis of (+)-AM-1 was obtained through a not previously described lipase catalyzed kinetic resolution of (±)-lupinine. In terms of antimalarial activity, (±)-AM1 and (+)-AM1 demonstrated very good activity in vitro against both CQ-R and CQ-S strains of P. falciparum (range IC₅₀ 16–35 nM), and low toxicity against human normal cell lines (therapeutic index >1000), comparable with that of (?)-AM1. These results confirm that the racemate (±)-AM1 could be considered as a potential antimalarial agent, ensuring a decrease of costs of synthesis compared to (?)-AM1.     

Synthesis of Macrotetrolide α, a Designed Polynactin Analog Composed of (+)- and (−)-Bishomononactic Acids

Macrotetrolide α, a designed analog of polynactin composed of (+)- and (?)-bishomononactic acids, was synthesized. These monomers were prepared via optical resoiution of the corresponding (S)-O-acetylmandelates. Assembly of the monomers to macrotetrolide α took seven steps without any loss of the intermediates.     

First Stereoselective Synthesis of meso-Secoisolariciresinol and Comparison of Its Biological Activity with (+) and (−)-Secoisolariciresinol

The first stereoselective synthesis of meso-secoisolariciresinol is reported. A comparison of the cytotoxic and immunosuppressive activity between meso-secoisolariciresinol and optically active secoisolariciresinols was similarly performed for the first time. Both enantiomers of secoisolariciresinol accelerated IgM production, although meso-secoisolariciresinol did not affect IgM production. Only meso-secoisolariciresinol showed cytotoxic activity.     

Synthesis of (S)-(—)-Vertinolide

(S)-(?)-Vertinolide 1 was synthesized via the tetronic acid derivative 6 from (S)-(?)-tetrahydro-2-methyl-5-oxo-2-furancarboxylic acid 3. (±)-Vertinolide was also synthesized from (±)-3.     

5′-O-Aliphatic and amino acid ester prodrugs of (−)-β-d-(2R,4R)-dioxolane-thymine (DOT): Synthesis,anti-HIV activity,cytotoxicity and stability studies

A series of (?)-β-d-(2R,4R)-dioxolane-thymine-5′-O-aliphatic acid esters as well as amino acid esters were synthesized as prodrugs of (?)-β-d-(2R,4R)-dioxolane-thymine (DOT). The compounds were evaluated for anti-HIV activity against HIV-1_LAI in human peripheral blood mononuclear (PBM) cells as well as for their cytotoxicity in PBM, CEM and Vero cells. Improved anti-HIV potency in vitro was observed for the compound 2–4 (5′-O-aliphatic acid esters) without increase in cytotoxicity in comparison to the parent drug. Chemical and enzymatic hydrolysis of the prodrugs was also studied, in which the prodrugs exhibited good chemical stability with the half-lives from 3 h to 54 h at pH 2.0 and 7.4 phosphate buffer. However, the prodrugs were relatively labile to porcine esterase with the half-lives from 12.3 to 48.0 min.     

Synthesis of (R)- or (S)-valinol using ω-transaminases in aqueous and organic media

Valinol is part of numerous pharmaceuticals and has various other important applications. Optically pure valinol (ee >99%) was prepared employing different ω-transaminases from the corresponding prochiral hydroxy ketone. By the choice of the enzyme the (R)- as well as the (S)-enantiomer were accessible. Reductive amination was performed in organic solvent (MTBE) using 2-propyl amine as amine donor whereas alanine was applied in or in aqueous medium. Transformations in phosphate buffer were successfully performed even at 200 mM substrate concentration (20.4 g/L) leading to 99% (R) and 94% (S) conversion with perfect optical purity (>99% ee).     

Synthesis and antitumor activity of β-carboline 3-(substituted-carbohydrazide) derivatives

A series of β-carboline derivatives bearing a substituted-carbohydrazide moiety at C-3 were synthesized and evaluated for their antitumor activity against eight human cancer cell lines. The β-carboline N-(substituted-benzylidene)carbohydrazides showed, in general, a greater antitumor activity than their N-(alkylidene)carbohydrazide analogues. The N(9)-methylation of β-carboline N-(substituted-benzylidene) carbohydrazides resulted in a decrease of antitumor activity. Among compounds tested, the benzylidene-carbohydrazides 3, 4, 11, 13, 16, 21 and 22 were the most active, possessing IC(50) less than 10 μM for six of the eight tumor cell lines assayed. The derivative 4 displayed the most significant activity toward all tested cell lines, with a remarkable cytotoxicity against renal (786-0) cell lines (IC(50)=0.04 μM). Compound 4 was assayed for its in vivo antineoplastic activity in the Ehrlich solid carcinoma assay.     

Synthesis,antiviral activity and structure–activity relationship of 1-(1-aryl-4,5-dihydro-1H-imidazoline)-3-chlorosulfonylureas and products of their cyclization

Novel 1-(1-aryl-4,5dihydro-1H-imidazoline)-3-chlorosulfonylourea derivatives 3a–3f were synthesized in the reaction of 1-aryl-4,5-dihydro-1H-imidazol-2-amines with chlorosulfonyl isocyanate. The second series of compounds 4a–4f was prepared from the respective 1-(1-aryl-4,5-dihydro-1H-imidazoline)-3-chlorsulfonylureas 3a–3f and 1,1′-carbonyldiimidazole (CDI). The selected compounds were tested for their activity against Herpes simplex virus and coxsackievirus B3 (CVB3). It was determined that three derivatives, i.e 3d, 4a and 4d are active against Herpes simplex virus (HSV-1). Compounds 3d and 4c are active against CVB3. Their favorable activity can be primarily attributed to their low lipophilicity values. Moreover, the lack of substituent in the phenyl moiety or 4-methoxy substitution can be considered as the most beneficial for the antiviral activity.     

Synthesis and evaluation of (−)- and (+)-[11C]galanthamine as PET tracers for cerebral acetylcholinesterase imaging

Improved radiopharmaceuticals for imaging cerebral acetylcholinesterase (AChE) are needed for the diagnosis of Alzheimer’s disease (AD). Thus, ¹¹C-labeled (−)-galanthamine and its enantiomers were synthesized as novel agents for imaging the localization and activity of AChE by positron emission tomography (PET). C-11 was incorporated into (−)- and (+)-[¹¹C]galanthamine by N-methylation of norgalanthamines with [¹¹C]methyl triflate. Simple accumulation of ¹¹C in the brain was measured in an in vivo biodistribution study using mice, whilst donepezil was used as a blocking agent in analogous in vivo blocking studies. In vitro autoradiography of rat brain tissue was performed to investigate the distribution of (−)-[¹¹C]galanthamine, and confirmed the results of PET studies in mice. The radiochemical yields of N-methylation of (−)- and (+)-norgalanthamines were 13.7% and 14.4%, respectively. The highest level of accumulation of ¹¹C in the brains of mice was observed at 10 min after administration (2.1% ID/g). Intravenous pretreatment with donepezil resulted in a 30% decrease in accumulation of (−)-[¹¹C]galanthamine in the striatum; however, levels in the cerebellum were unchanged. In contrast, use of (+)-[¹¹C]galanthamine led to accumulation of radioactivity in the striatum equal to that in the cerebellum, and these levels were unaffected by pretreatment with donepezil. In in vitro autoradiography of regional radioactive signals of brain sections showed that pretreatment with either (−)-galanthamine or donepezil blocked the binding of (−)-[¹¹C]galanthamine to the striatum, while sagittal PET imaging revealed accumulation of (−)-[¹¹C]galanthamine in the brain. These results indicate that (−)-[¹¹C]galanthamine showed specific binding to AChE, whereas (+)-[¹¹C]-galanthamine accumulated in brain tissue by non-specific binding. Thus, optically pure (−)-[¹¹C]galanthamine could be a useful PET tracer for imaging cerebral AChE.     

Synthesis of derivatives of cleistopholine and their anti-acetylcholinesterase and anti-β-amyloid aggregation activity

A series of 6- and 9-substituted cleistopholine derivatives has been designed, synthesized and investigated to inhibit the aggregation of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and β-myloid (A β). Results showed that these synthetic compounds had excellent AChE inhibitory activity and a significant in vitro inhibitory potency toward the self-induced A β aggregation. When SH-SY5Y cells were treated with these substituted cleistopholine derivatives during they overexpressed the Swedish mutant form of human β -amyloid precursor protein (APPsw), A β 42 secretion levels were significantly reduced. According to a parallel artificial membrane permeation assay for BBB, seven out of these sixteen synthetic compounds probably could cross the blood-brain barrier (BBB) to reach their targets in the central nervous system (CNS).     

Enzymatic activity of cell-free extracts from Burkholderia oxyphila OX-01 bio-converts (+)-catechin and (−)-epicatechin to (+)-taxifolin

This study characterized the enzymatic ability of a cell-free extract from an acidophilic (+)-catechin degrader Burkholderia oxyphila (OX-01). The crude OX-01 extracts were able to transform (+)-catechin and (?)-epicatechin into (+)-taxifolin via a leucocyanidin intermediate in a two-step oxidation. Enzymatic oxidation at the C-4 position was carried out anaerobically using H₂O as an oxygen donor. The C-4 oxidation occurred only in the presence of the 2R-catechin stereoisomer, with the C-3 stereoisomer not affecting the reaction. These results suggest that the OX-01 may have evolved to target both (+)-catechin and (?)-epicatechin, which are major structural units in plants.     

Stereoselective Synthesis of (2R, 3S)-2-Benzyl-2-hydroxy-3- (3,4-methylenedioxybenzyl)-γ-butyrolactone from L-(+)-Arabinose

As a model experiment for the stereoselective synthesis of optically active cis-α,β-dibenzyl-α-hydroxy-γ-butyrolactone, (2R, 3S)-2-benzyl-2-hydroxy-3-(3,4-methylenedioxybenzyl)-γ-butyrolactone (3) was stereoselectively synthesized from L-(+)-arabinose.     

Photobromination of 1,5-Anhydro-2,3-O-isopropylidene-β-d-ribofuranose and Synthesis of (5R) and (5S)-(5-2H1)-d-Riboses

The photobromination of 1,5-anhydro-2,3-O-isopropylidene-β-d-ribofuranose gave the corresponding (5S)-5-bromo compound. The reduction of the bromide with triphenyltindeuteride gave (5S)-(5-²H₁)-1,5-anhydro-2,3-O-isopropylidene-β-d-ribofuranose, with a chiral purity of 76% at C-5, which was converted to (5R)- and (5S)-(5-²H₁)-d-riboses and other ribofuranose derivatives.     

Selective biocatalytic aminolysis of (±)-epichlorohydrin: synthesis and ICAM-1 inhibitory activity of (S)-(+)-3-arylamino-1-chloropropan-2-ols

Regio- and enantioselective synthesis of (S)-(+)-3-arylamino-1-chloropropan-2-ols has been achieved by the epoxide ring opening of (±)-epichlorohydrin with different aromatic amines in the presence of Candida rugosa lipase. Activities of seven model (S)-(+)-3-arylamino-1-chloropropan-2-ols, out of 10 compounds synthesized, have been evaluated for the inhibition of tumor necrosis factor-α TNF-α) induced expression of intercellular adhesion molecule-1 (ICAM-1), which is one of the factors responsible for the modulation of inflammation in biological systems; (S)-(+)-1-chloro-3-(2'-chlorophenylamino)-propan-2-ol has been found to exhibit highest activity, that is, 86% inhibition of TNF-α induced expression of ICAM-1 at a concentration of 40 μg/ml.