Mechanistic study of the biosynthesis of R-phenylcarbinol by acetohydroxyacid synthase enzyme using hybrid quantum mechanics/molecular mechanics simulations.

The biosynthesis of R-phenylacetylcarbinol (R-PAC) by the acetohydroxy acid synthase, (AHAS) is addressed by molecular dynamics simulations (MD), hybrid quantum mechanics/molecular mechanics (QM/MM), and QM/MM free energy calculations. The results show the reaction starts with the nucleophilic attack of the C2α atom of the HEThDP intermediate on the Cß atom of the carbonyl group of benzaldehyde substrate via the formation of a transition state (TS1) with the HEThDP intermediate under 4'-aminopyrimidium (APH+) form. The calculated activation free energy for this step is 17.4kcal mol-1 at 27 °C. From this point, the reaction continues with the abstraction of Hß atom of the HEThDP intermediate by the Oß atom of benzaldehyde to form the intermediate I. The reaction is completed with the cleavage of the bond C2α-C2 to form the product R-PAC and to regenerate the ylide intermediate under the APH+ form, allowing in this way to reinitiate to the catalytic cycle once more. The calculated activation barrier for this last step is 15.9kcal mol-1 at 27 °C.

One-Pot Cascade Biotransformation for Efficient Synthesis of Benzyl Alcohol and Its Analogs.

Benzyl alcohol is a naturally occurring aromatic alcohol and has been widely used in the cosmetics and flavor/fragrance industries. The whole-cell biotransformation for synthesis of benzyl alcohol directly from bio-based L-phenylalanine (L-Phe) was herein explored using an artificial enzyme cascade in Escherichia coli. Benzaldehyde was first produced from L-Phe via four heterologous enzymatic steps that comprises L-amino acid deaminase (LAAD), hydroxymandelate synthase (HmaS), (S)-mandelate dehydrogenase (SMDH) and benzoylformate decarboxylase (BFD). The subsequent reduction of benzaldehyde to benzyl alcohol was achieved by a broad substrate specificity phenylacetaldehyde reductase (PAR) from Solanum lycopersicum. We found the designed enzyme cascade could efficiently convert L-Phe into benzyl alcohol with conversion above 99%. In addition, we also examined L-tyrosine (L-Tyr) and m-fluoro-phenylalanine (m-f-Phe) as substrates, the cascade biotransformation could also efficiently produce p-hydroxybenzyl alcohol and m-fluoro-benzyl alcohol. In summary, the developed biocatalytic pathway has great potential to produce various high-valued fine chemicals.

Anti-Cancer Effects of Synergistic Drug-Bacterium Combinations on Induced Breast Cancer in BALB/c Mice.

Cancer development and progression are extremely complex due to the alteration of various genes and pathways. In most cases, multiple agents are required to control cancer progression. The purpose of this study is to investigate, using a mouse model, the synergistic interactions of anti-cancer agents, 1'-S-1'-acetoxychavicol acetate (ACA), Mycobacterium indicus pranii (MIP), and cisplatin (CDDP) in double and triple combinations to treat chemo-sensitize and immune-sensitize breast cancer. Changes in tumor volume and body weight were monitored. Organs were harvested and stained using hematoxylin-eosin for histopathological assessment. Milliplex enzyme-linked immunosorbent assay (ELISA) was performed to determine cytokine levels, while immunohistochemistry (IHC) was conducted on tumor biopsies to verify systemic drug effects. In vivo mouse models showed tumor regression with maintenance of regular body weight for all the different treatment regimens. IHC results provided conclusive evidence indicating that combination regimens were able to down-regulate nuclear factor kappa-B activation and reduce the expression of its regulated pro-inflammatory proteins. Reduction of pro-inflammatory cytokines (e.g., IL-6, TNF-α, and IFN-É£) levels were observed when using the triple combination, which indicated that the synergistic drug combination was able to significantly control cancer progression. In conclusion, ACA, MIP, and CDDP together serve as promising candidates for further development and for subsequent clinical trials against estrogen-sensitive breast cancer.

Design, Synthesis, and Characterization of Ogerin-Based Positive Allosteric Modulators for G Protein-Coupled Receptor 68 (GPR68).

G protein-coupled receptor 68 (GPR68) is an understudied orphan G protein-coupled receptor (GPCR). It is expressed most abundantly in the brain, potentially playing important roles in learning and memory. Pharmacological studies with GPR68 have been hindered by lack of chemical tools that can selectively modulate its activity. We previously reported the first small-molecule positive allosteric modulator (PAM), ogerin (1), and showed that 1 can potentiate proton activity at the GPR68-Gs pathway. Here, we report the first comprehensive structure-activity relationship (SAR) study on the scaffold of 1. Our lead compound resulted from this study, MS48107 (71), displayed 33-fold increased allosteric activity compared to 1. Compound 71 demonstrated high selectivity over closely related proton GPCRs and 48 common drug targets, and was bioavailable and brain-penetrant in mice. Thus, our SAR study has resulted in an improved GPR68 PAM for investigating the physiological and pathophysiological roles of GPR68 in vitro and in vivo.

Regioselective synthesis of gentisyl alcohol-type marine natural products.

Gentisyl alcohol-type natural products, possessing various important biological properties, have been synthesized from 4-methoxyphenol by using a selective phenol monohydroxymethylation/monochlorination, a CAN oxidation and a sodium dithionite reduction as the key steps. The natural product synthesis is efficient, atom- and step-economical, and requires no protecting groups.

Anti-proliferative, apoptotic induction, and anti-migration effects of hemi-synthetic 1'S-1'-acetoxychavicol acetate analogs on MDA-MB-231 breast cancer cells.

Nine analogs of 1'S-1'-acetoxychavicol acetate (ACA) were hemi-synthesized and evaluated for their anticancer activities against seven human cancer cell lines. The aim of this study was to investigate the anti-proliferative, apoptotic, and anti-migration effects of these compounds and to explore the plausible underlying mechanisms of action. We found that ACA and all nine analogs were non toxic to human mammary epithelial cells (HMECs) used as normal control cells, and only ACA, 1'-acetoxyeugenol acetate (AEA), and 1'-acetoxy-3,5-dimethoxychavicol acetate (AMCA) inhibited the growth of MDA-MB-231 breast cancer cells with a half-maximal inhibitory concentration (IC50) value of <30.0 µM based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay results, and were selected for further investigation. DNA fragmentation assays showed that these three compounds markedly induced apoptosis of MDA-MB-231 cells. Western blot analysis revealed increased expression levels of cleaved PARP, p53, and Bax, while decreased expression levels of Bcl-2 and Bcl-xL were seen after treatment, indicating that apoptosis was induced via the mitochondrial pathway. Moreover, ACA, AEA, and AMCA effectively inhibited the migration of MDA-MB-231 cells. They also downregulated the expression levels of pFAK/FAK and pAkt/Akt via the integrin ß1-mediated signaling pathway. Collectively, ACA and its hemi-synthetic analogs, AEA and AMCA are seen as potential anticancer agents following their abilities to suppress growth, induce apoptosis, and inhibit migration of breast cancer cells.

Resorcinol-, catechol- and saligenin-based bronchodilating ß2-agonists as inhibitors of human cholinesterase activity.

We investigated the influence of bronchodilating ß2-agonists on the activity of human acetylcholinesterase (AChE) and usual, atypical and fluoride-resistant butyrylcholinesterase (BChE). We determined the inhibition potency of racemate and enantiomers of fenoterol as a resorcinol derivative, isoetharine and epinephrine as catechol derivatives and salbutamol and salmeterol as saligenin derivatives. All of the tested compounds reversibly inhibited cholinesterases with Ki constants ranging from 9.4 µM to 6.4 mM and had the highest inhibition potency towards usual BChE, but generally none of the cholinesterases displayed any stereoselectivity. Kinetic and docking results revealed that the inhibition potency of the studied compounds could be related to the size of the hydroxyaminoethyl chain on the benzene ring. The additional π-π interaction of salmeterol's benzene ring and Trp286 and hydrogen bond with His447 probably enhanced inhibition by salmeterol which was singled out as the most potent inhibitor of all the cholinesterases.

Practical large-scale production of dihydrocapsiate, a nonpungent capsaicinoid-like substance.

Capsinoids represent a novel group of capsaicinoid-like substances found in a nonpungent cultivar, Capsicum annuum "CH-19 Sweet." They have capsaicinoid-like physiological and biological properties while lacking the harmful stimuli of capsaicinoids. A large-scale synthesis of dihydrocapsiate (DCT) is established in this work. 8-Methynonanoic acid (MNA) was synthesized by copper-catalyzed cross-coupling of ethyl 6-bromohexanoate with isobutylmagnesium bromide and subsequent hydrolysis. Lipase-catalyzed chemoselective esterification of vanillyl alcohol and MNA was performed at 50 °C under reduced pressure to remove water without solvents or drying agents. A slightly larger stoichiometric amount of MNA was used and the purification in the final stage was simplified to leave a small amount of MNA in the product, because we found that the presence of a small amount of MNA is necessary to stabilize DCT. DCT was synthesized according to the production, and stabilization methods described here has been filed as a new dietary ingredient.

Single-Electron Transmetalation: Protecting-Group-Independent Synthesis of Secondary Benzylic Alcohol Derivatives via Photoredox/Nickel Dual Catalysis.

Protecting-group-independent cross-coupling of α-alkoxyalkyl- and α-acyloxyalkyltrifluoroborates with aryl and heteroaryl bromides is achieved through application of photoredox/nickel dual catalysis. Reactions occur under exceptionally mild conditions, with outstanding functional group compatibility and excellent observed tolerance of heteroarenes. This method offers expedient access to protected secondary benzylic alcohol motifs bearing benzyl, pivaloyl, and N,N-diisopropylcarbamoyl protecting groups.

Direct Catalytic Synthesis of Unprotected 2-Amino-1-Phenylethanols from Alkenes by Using Iron(II) Phthalocyanine.

Aryl-substituted amino alcohols are privileged scaffolds in medicinal chemistry and natural products. Herein, we report that an exceptionally simple and inexpensive Fe(II) complex efficiently catalyzes the direct transformation of simple alkenes into unprotected amino alcohols in good yield and perfect regioselectivity. This new catalytic method was applied in the expedient synthesis of bioactive molecules and could be extended to aminoetherification.

Pharmacological characterization of a novel gastrodin derivative as a potential anti-migraine agent.

Migraine is a highly prevalent neurovascular disorder in the brain. An optimal therapy for migraine has not yet been developed. Gastrodin (Gas), the main effective constitute from Gastrodiae Rhizoma (Tianma in Chinese), has been indicated for migraine treatment and prophylaxis more than 30 years, with demonstrated safety. However, Gas is a phenolic glycoside, with relatively low concentrations and weak efficacy in the central nervous system. To develop more effective anti-migraine agents, we synthesized a novel Gas derivative (Gas-D). In the present study, comparative pharmacodynamic evaluations of Gas and Gas-D were performed in a model of nitroglycerin (NTG)-induced migraine in rats and the hot-plate test in mice. Following behavioral testing in this migraine model, external jugular vein blood and the trigeminal nucleus caudalis (TNC) were collected to analyze plasma nitric oxide (NO) and calcitonin gene-related peptide (CGRP) concentrations and c-Fos expression in the TNC. The acute oral toxicity of Gas and Gas-D was also examined. We found that Gas-D had potent anti-migraine effects, likely attributable to inhibition of both trigeminal nerve activation at central sites and the peripheral release of CGRP following NO scavenging. Additionally, Gas-D exerted significant anti-nociceptive effect in response to thermal pain compared with Gas. Furthermore, a single dose of 2.048 g/kg Gas or Gas-D presented no acute oral toxicity in mice. Altogether, the potent anti-migraine and anti-hyperalgesic effects of Gas-D suggest that it might be a potentially novel drug candidate for migraine treatment or prophylaxis.

Dynamic assembly of a zinc-templated bifunctional organocatalyst in the presence of water for the asymmetric aldol reaction.

A bifunctional organocatalytic system consisting of simple pyridine ligands containing separate catalytic functionalities was assembled using ZnCl2. This novel metal-templated catalyst furnished high yields and stereoselectivities towards the aldol reaction. The addition of controlled amounts of water turned out to be crucial to dissolve the system and achieve optimal results.

Easy preparation of enantiomerically enriched heteroaromatic alcohols through lipase-catalyzed acylation with succinic anhydride under unconventional activation.

This study reports the lipase-catalyzed resolution of heteroaromatic secondary alcohols by succinic anhydride under different activation conditions by convenient procedure with succinic anhydride. The effects of succinic anhydride and the nature of the heteroatom are discussed in standard conditions in the kinetic resolution with lipases. The results recorded under microwave activation and ultrasonication is compared. (R)-4-chromanol was obtained in optically pure form (ee > 99%) with a high selectivity E > 200 by Pseudomonas cepacia lipase (PCL) in diethyl ether, using microwave radiation and under ultrasonication. The reaction time is reduced compared to the conventional heating with a better control of the selectivity of the lipase PCL. A significant effect of the nature of the heteroatoms on the reactivity and selectivity of the lipase with succinic anhydride has been disclosed, regardless the conditions of activation. This method proved to be clean, fast, interesting alternative, and facilitates the use of a cyclic anhydride, by microwave or ultrasound especially with secondary alcohols. The process is a valuable prerequisite for the preparative scale production of enantiomerically heteroaromatic alcohols in sustainable chemistry.

Design and synthesis of novel 1,2-dithiolan-4-yl benzoate derivatives as PTP1B inhibitors.

A series of novel 1,2-dithiolan-4-yl benzoate compounds were synthesized and evaluated for in vitro PTP1B inhibitory activity. Some derivatives exhibited improved PTP1B inhibitory activity and selectivity compared to hit 6a, a compound from in-house library screening inspired by marine cyclic disulfide. The preliminary SAR analysis with assistance of molecular modeling approach revealed 6j (IC50=0.59µM) as the most potent PTP1B inhibitor among all derivatives.

Asymmetric syntheses and bio-evaluation of novel chiral esters derived from substituted tetrafluorobenzyl alcohol.

A series of novel chiral esters derived from tetrafluorobenzyl alcohol were designed and prepared via asymmetric synthesis. The target molecules have been identified on the basis of analytical spectra data. All newly synthesized compounds have been screened their potential insecticidal activity against Plutella xylostella compared with those of fenvalerate and d-trans-phenothrin by standard method, and the respective pairs of enantiomers (3-B1-R/S, 3-C1-R/S, 3-D1-R/S) indicated significantly different activities.

Synthesis of acyl derivatives of salicin, salirepin, and arbutin.

The total synthesis of two natural phenolglycosides of the family Salicaceae, namely: populoside and 2-(ß-d-glucopyranosyloxy)-5-hydroxy benzyl (3-methoxy-4-hydroxy) cinnamoate and nine not found yet in plants acyl derivatives of phenoglycosides: 2-(ß-d-glucopyranosyloxy)-benzylcinnamoate, 2-(ß-d-glucopyranosyloxy)-benzyl (4-hydroxy) benzoate, 2-(ß-d-glucopyranosyloxy)-benzyl (3-methoxy-4-hydroxy) benzoate, 2-(ß-d-glucopyranosyloxy)-5-hydroxy benzyl (3,4-dihydroxy) cinnamoate, 2-(ß-d-glucopyranosyloxy)-5-hydroxy benzylcinnamoate, 2-(ß-d-glucopyranosyloxy)-5-hydroxy benzyl (4-hydroxy) benzoate, 2-(ß-d-glucopyranosyloxy)-5-hydroxy benzyl (3-methoxy-4-hydroxy) benzoate, 2-(ß-d-glucopyranosyloxy)-5-benzoyloxy benzylbenzoate and 4-(ß-d-glucopyranosyloxy)-phenylbenzoate, starting from readily available phenols and glucose was developed for the first time.

Palladium catalyzed acetoxylation of benzylic C-H bonds using a bidentate picolinamide directing group.

A general palladium catalyzed acetoxylation of benzylic C-H bonds has been developed. Picolinamides serve as an excellent directing group for the C-H activation of benzylic methyls. A wide range of 2-amino benzyl alcohol analogues were synthesized in good yields. The products demonstrated broad synthetic utilities toward various benzo-fused heterocycles. Mechanistic studies revealed the key rate-limiting C-H insertion step, which could be affected by the substitution pattern of the parent arene.

Synthetically modified bioisosteres of salicyl alcohol and their gastroulcerogenic assessment versus aspirin: biochemical and histological correlates.

The present study was conducted to synthesize nitrogen containing derivatives of salicyl alcohol and to investigate in vivo their ulcerogenic potential in comparison with aspirin in rats. The compounds [4-(2-hydroxybenzyl) morpholin-4-iumchloride (I)] and [1,4-bis(2-hydroxybenzyl) piperazine-1,4-diium chloride (II)] were synthesized and their chemical structures were characterized using spectral data. In our previous study (Ali et al., Afr J Pharm Pharmacol 7:585-596, 2013), both compounds showed anti-inflammatory, antinociceptive, and antipyretic properties in standard animal models and a greater binding affinity for cyclooxygenase-2 versus cyclooxygenase-1 in molecular docking and dynamics analysis. For in vivo studies, animals were randomly divided into four groups. The synthetic compounds (both at 100 or 150 mg/kg), aspirin (150 mg/kg), or saline vehicle was administered orally, once daily for 6 days and then tested for ulcerogenic activity. At the end of the procedure, gastric juice and tissues were collected and subjected to biochemical and histological analyses. The results of the study revealed that in the case of the aspirin-treated group, there was a significant increase in gastric juice volume, free acidity, total acidity, and ulcer score and a decrease in gastric pH. Moreover, histological examination of the gastric mucosa of the aspirin-treated group indicated morphological changes while neither of the synthetic compounds showed any significant ulcerogenic or cytotoxic properties. The results of the present study suggest that both compounds are free from ulcerogenic side effects and may represent a better alternative to aspirin.

Synthesis of single-enantiomer bioactive molecules: a brief overview.

Chiral-center enantiomers have been shown to differ significantly in biological activity, pharmacodynamics, pharmacokinetics and toxicity. New developments in the stereoselective organic synthesis have enriched the vast literature of synthetic methodologies applicable to access natural products as well as bioactive molecules. These compounds also include new drugs, drug candidates and reagents used to explore biological processes. The article reviews the synthesis of optically pure drugs, biologically active intermediates and amino alcohols by using different methods.

Chirally deuterated benzyl chlorides from benzyl alcohols via hexachloroacetone/polymer-supported triphenylphosphine: synthesis of protected (2S, 3S)-[3-(2)H, (15)N]-tyrosine.

Chirally deuterated benzyl chlorides were prepared using novel, general hexachloroacetone/polymer-supported triphenylphosphine treatment of chirally deuterated benzyl alcohols. Doubly labeled protected tyrosine was obtained in 62% yield with 86% de at the α-carbon and 82% de at the ß-carbon. Key in the synthesis was the alkylation of (15)N-labeled (-)-8-phenylmenthylhippurate with R-(-)-4-triisopropylsilyloxybenzyl-α-d chloride.