Phenylcarbamate Derivatives Research Articles

Synthesis of amylose and cellulose derivatives bearing bulky pendants for high-efficient chiral fluorescent sensing

Three novel amylose and cellulose phenylcarbamate derivatives bearing bulky para-substituted benzothienyl or benzofuranyl pendants were successfully synthesized as chiral fluorescent sensors through carbamoylation followed by Suzuki-Miyaura coupling reactions. The bulky derivatives showed good enantioselective fluorescent sensing properties toward a total of eight chiral quenchers in this study. Especially, a high enantiomeric fluorescence difference ratio (ef = 164.35) was achieved on amylose benzofuranylphenylcarbamates (Amy-2) to the 3-amino-3-phenylpropan-1-ol (Q5), an important chiral drug intermediate. It indicated that a favorable chiral environment was effectively constructed by arrangement of bulky π-conjugated benzothienyl or benzofuranyl pendants on the phenylcarbamate moieties surrounding the helical backbone, which is crucial for high-efficient chiral fluorescent sensing. As chiral stationary phases for high-performance liquid chromatography, the bulky benzothienylphenylcarbamates of amylose and cellulose also showed good resolution powers to thirteen racemates, including metal tris(acetylacetonate) complexes, chiral drugs, analytes with axial chirality and chiral aromatic amines, which were difficult to be efficiently separated even on the popular Chiralpak AD and Chiralcel OD. The excitation-dependent chiral fluorescent sensing probably followed different mechanisms from that for chromatographic enantioseparation relying on the dynamic collision of molecules in the ground state. The structure of the bulky derivatives was also investigated by CD spectra and POM microscopy.

Enantioselective Green HPLC Method for Simultaneous Determination of Enantiomer, and Potential Impurities in Apremilast Drug Substance

A single reversed-phase HPLC method was developed for the quantification of seven impurities of Apremilast and its enantiomer in the drug substance. An immobilized chiral stationary phase with a chiral selector “tris (3,5-dimethyl phenyl carbamate) derivative of amylose-Chiralpak IA-3 (250 mm × 4.6 mm, 3 μm) was employed to achieve the desired separation. A mobile phase consists of buffer (0.01M NH4HCO3, PH 8.0) and acetonitrile in the ratio 50:50 (v/v) and is pumped at a flow rate of 0.4 mL/min with an isocratic elution mode. The column oven temperature is set at 25°C, and the chromatographic output is monitored at 225 nm with a total run time of 45 min. A test concentration of 500 µg/mL of Apremilast in the mobile phase is used with an injection volume of 10 µL. Induced degradation studies were carried out to study the intrinsic chemical behavior of the drug. The degradation sample solutions were utilized to demonstrate the stability-indicating nature of the developed analytical method. The obtained mass number [M+H]+ for the primary degradation product formed in acid hydrolysis was identified as 418.36 and in base hydrolysis 478.12. The two impurities were identified as impurity-5(Deacetylated impurity), and impurity-2(open ring acid impurity), respectively, and the degradation pathways were established. Following ICH Q2 and USP<1225>guidelines, complete method validation was carried out. The RSD for the drug and impurities in interday and intraday studies are less than 4.0%, and the recoveries for the impurities are between 96.1-102.1% and linearity r ≥ 0.9997. LOQ results for the drug and impurities are between 0.052 µg/mL and 0.107 µg/mL, and LOD results are between 0.016 µg/mL and 0.032 µg/mL. The greenness of the method was evaluated by using an analytical eco scale, GAPI, and AGREE, and it was found that the method is green.

Preparation of cellulose derivative bearing bulky 4-(2-benzothienyl)phenylcarbamate substituents as chiral stationary phase for enantioseparation.

A novel cellulose derivative bearing bulky 4-(2-benzothienyl)phenylcarbamate substituents (Cel-1) was readily synthesized by carbamoylation followed by Suzuki-Miyaura coupling reaction. The corresponding coated-type chiral stationary phase (CSP) was prepared on basis of the derivative, and its chiral recognition ability was then evaluated by high-performance liquid chromatography (HPLC). The chiral recognition ability of the cellulose derivative was greatly influenced by introduction of the bulky benzothienyl pendants on the aromatic moieties of phenylcarbamates, compared with its analog with smaller groups. Many racemates, including the metal tris(acetylacetonate) complexes, chiral drug, and the analyte with axial chirality, were sufficiently separated with good enantioselectivities on Cel-1. Some of them were even higher than those on the commercially powerful Chiralcel OD, which is also a coated-type CSP derived from cellulose phenylcarbamate derivative containing smaller 3,5-dimethyl pendants. The 1 H NMR and circular dichroism (CD) spectra of Cel-1 indicated that the obtained derivative possessed a regular higher order structure, and a strong cotton effect was observed within the absorption range of π-conjugated pendant at 350-500 nm. Impressively, the cellulose derivative bearing the bulky 4-(2-benzothienyl)phenylcarbamates exhibited good enantioselective fluorescence quenching behavior to the enantiomer pair of 1-phenylethylamine, probably suggesting its potential for the application as a chiral fluorescent sensor with high efficiency. The combination of the arrangement of bulky π-conjugated benzothienyl pendants on the phenylcarbamate moieties surrounding the helical backbone and the regular higher order structure of the polymer itself probably played a key role for this high chiral fluorescent recognition ability of Cel-1. The interaction sites of bulky 4-(2-benzothienyl)phenylcarbamate pendants in its excited state can exhibit higher enantioselective discrimination via fluorescent response to the chiral compound Q1, whereas the chiral recognition ability of Cel-1 to the same compound in the ground state had no clear improvement.

Influence of the substituents on phenyl groups on enantioseparation property of amylose phenylcarbamates

A series of amylose phenylcarbamate derivatives bearing different chloro- or/and methyl- substituents on the phenyl groups were synthesized and their enantioseparation properties were examined by high-performance liquid chromatography. The enantioseparation power considerably altered due to the substituents on the phenyl units. The amylose derivative bearing 3-chloro-5-methyl disubstituents seemed to possess much higher chiral resolution power. The introduction of both an electron-withdrawing chloro and an electron-donating methyl groups enabled the NH groups to contain a moderate acidity, which may be important to construct a regular secondary structure for the amylose phenylcarbamates. Some interesting observations in 1H NMR and circular dichroism spectroscopy demonstrated the correlations between the structure and enantioseparation ability. The electronegativity, location and amount of the substituents at the phenyl residues have great influence on the enantioseparation power of the amylose derivatives. The mechanism involved in enantioselective discrimination of the amylose phenylcarbamates was further investigated by the molecular docking simulation.

Palladium-catalyzed C(carbonyl)-C bond cleavage of amides: a facile access to phenylcarbamate derivatives with alcohols.

A sulfur-containing auxiliary enabled palladium-catalyzed C(carbonyl)-C bond activation of amides was reported to form phenylcarbamate derivatives with alcohols. Both alkyl and benzyl alcohols could be employed well with yields up to 85%. Derivations from phenylcarbamates to ureas and thiocarbamates illustrated the potential applications of this sequential C-C cleavage/C-O coupling reaction.

Synthesis of tert-butyl (substituted benzamido)phenylcarbamate derivatives: anti-inflammatory activity and docking studies.

A series of new tert-butyl 2-(substituted benzamido) phenylcarbamate (4a-4j) were synthesized by the condensation of tert-butyl 2-amino phenylcarbamate (3) with various substituted carboxylic acid in the presence of EDCI and HOBt as coupling reagent, obtain in excellent yields. The structures of all newly synthesized compounds were characterized spectroscopically and evaluated for in vivo anti-inflammatory activity compared to the standard drug, indomethacin, by using the carrageenan-induced rat paw edema protocol. Most of the compounds exhibited a promising anti-inflammatory activity within 9 to 12h, the percentage of inhibition values ranging from 54.239 to 39.021%. The results revealed that the compounds 4i and 4a exhibited better or equivalent anti-inflammatory activity with the percentage of inhibition of 54.239 and 54.130%, respectively, which was comparable to standard drug. In addition to experimental results, in silico docking studies was used as a tool to verify and expand the experimental outcomes.

The dawn of chiral material development using saccharide-based helical polymers

Polysaccharides, such as cellulose and amylose, are abundant and optically active carbohydrate-based resources. Their suitably modified derivatives (for example, benzoate and phenylcarbamate derivatives) exhibit excellent resolution abilities for a wide variety of chiral compounds when applied to chiral stationary phases (CSPs) for high-performance liquid chromatography. Despite the established application of polysaccharides in CSP materials, their use in other chiral functional materials has been limited. In this review, the author describes the functionalization of cellulose and amylose to yield novel chiral functions other than those in CSPs, as well as the use of these materials for various applications, such as asymmetric organocatalysts, chiral auxiliaries and chiral fluorescent sensors. The synthesis of a saccharide-containing polymer via the polymerization of a glucose-based monomer and its application as a circularly polarized luminescence material are also described. The author has recently focused on exploring novel possibilities of cellulose and amylose, which exist in great abundance on earth. In this review, the author describes the functionalization of cellulose and amylose to give novel chiral functions other than that as chiral stationary phases and their use in applications, such as asymmetric organocatalysts, chiral auxiliaries and chiral fluorescent sensors. Furthermore, the application of a saccharide-containing helical polymer, which can be prepared through polymerization of a glucose-based monomer, to a circularly polarized luminescence material is also described.

Development of Amylose- and β-Cyclodextrin-Based Chiral Fluorescent Sensors Bearing Terthienyl Pendants.

Phenylcarbamate derivatives of amylose and β-cyclodextrin show excellent chiral recognition when used as chiral stationary phases (CSPs) for high-performance liquid chromatography. To open up new possibilities of carbohydrate-based materials, we developed chiral fluorescent sensors based on amylose and β-cyclodextrin (Am-1b and CyD-1b, respectively) by attaching fluorescent π-conjugated units on their side chains. Their recognition abilities toward chiral analytes containing a nitrophenyl unit were evaluated by measuring the enantioselective fluorescence quenching behavior. Both sensors showed the same degree of enantioselective fluorescence response for various aromatic nitro compounds. However, in some cases, their enantioselectivities were different depending on the analytes. The difference in the chiral recognition abilities between Am-1b and CyD-1b seems to be based on the structural difference of their inherent backbones, that is, the one-handed helical structure and cyclic structure, respectively. The study on the resolution ability of the Am-1b-based CSP revealed that the terthienyl-based pendant of Am-1b provides not only a fluorescent functionality but also a different chiral recognition site from that of amylose tris(phenylcarbamate).

Design, synthesis and in-vitro evaluation of novel tetrahydroquinoline carbamates as HIV-1 RT inhibitor and their antifungal activity

Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) are vital class of drugs in treating HIV-1 infection, but drug resistance and toxicity drive the need for effective new inhibitors with potent antiviral activity, less toxicity and improved physicochemical properties. In the present study, twelve novel 1-(4-chlorophenyl)-2-(3,4-dihydroquinolin-1(2H)-yl)ethyl phenylcarbamate derivatives were designed as inhibitor of HIV-1 RT using the ligand based drug design approach and in-silico evaluated for drug-likeness properties. Designed compounds were synthesized, characterized and in-vitro evaluated for RT inhibitory activity against wild HIV-1 RT. Among these, four compounds (6b, 6i, 6j and 6l) exhibited significant inhibition of HIV-1 RT (IC50⩽20μM). Among four compounds, most active compounds 6b and 6j inhibited the RT activity with IC50 8.12 and 5.42μM respectively. Docking studies of compounds 6b and 6j were performed against wild HIV-1 RT in order to predict their putative binding mode with selected target. Further, cytotoxicity and anti-HIV activity of compounds 6b and 6j were evaluated on T lymphocytes (C8166 cells). All the synthesized compounds were also evaluated for antifungal activity against Candida albicans and Aspergillus niger fungal strains.

Synthesis and Enantioseparation Ability of Xylan Bisphenylcarbamate Derivatives as Chiral Stationary Phases in HPLC.

Ten novel xylan bisphenylcarbamate derivatives bearing meta- and para-substituents on their phenyl groups were synthesized and their chiral recognition abilities were evaluated as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them on macroporous silica. The chiral recognition abilities of these CSPs depended on the nature, position, and number of the substituents on the phenyl moieties. The introduction of an electron-donating group was more attractive than an electron-withdrawing group to improve the chiral recognition ability of the xylan phenylcarbamate derivatives. Among the CSPs discussed in this study, xylan bis(3,5-dimethylphenylcarbamate)-based CSP seems to possess the highest resolving power for many racemates, and the meta-substituted CSPs showed relatively better chiral recognition than the para-substituted ones. For some racemates, the xylan bis(3,5-dimethylphenylcarbamate) derivative exhibited higher enantioselectivity than the CSP based on cellulose tris(3,5-dimethylphenylcarbamate).

Effect of basic and acidic additives on the separation of some basic drug enantiomers on polysaccharide-based chiral columns with acetonitrile as mobile phase.

The separation of enantiomers of 16 basic drugs was studied using polysaccharide-based chiral selectors and acetonitrile as mobile phase with emphasis on the role of basic and acidic additives on the separation and elution order of enantiomers. Out of the studied chiral selectors, amylose phenylcarbamate-based ones more often showed a chiral recognition ability compared to cellulose phenylcarbamate derivatives. An interesting effect was observed with formic acid as additive on enantiomer resolution and enantiomer elution order for some basic drugs. Thus, for instance, the enantioseparation of several β-blockers (atenolol, sotalol, toliprolol) improved not only by the addition of a more conventional basic additive to the mobile phase, but also by the addition of an acidic additive. Moreover, an opposite elution order of enantiomers was observed depending on the nature of the additive (basic or acidic) in the mobile phase.

Precision synthesis, structure and function of helical polymers.

Helical structures are chiral, which means that if we can synthesize a polymer having a stable one-handed helicity, the polymer is optically active. In 1979, we succeeded in the synthesis of a one-handed helical polymer from an optically inactive achiral monomer, triphenylmethyl methacrylate (TrMA). This is the first example of the asymmetric synthesis of an optically active one-handed helical polymer. The polymer (PTrMA) exhibited an unexpected high chiral recognition ability and afforded a practically useful chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) by coating it on silica gel. In addition, we also succeeded in the development of very useful CSPs for HPLC using the phenylcarbamate derivatives of polysaccharides, cellulose and amylose. These CSPs can efficiently resolve a broad range of chiral compounds, and have been used all over the world for separating and analyzing chiral compounds.

Tocopherol side chain synthesis via asymmetric organocatalytic transfer hydrogenation and convenient measurement of stereoselectivity

An asymmetric synthetic route for 1-iodofarnesane, a key intermediate for tocopherol side chain synthesis, starting from (+)-(R)-citronellal was developed. 1-Iodofarnesane was prepared through eight steps in about 50% overall yield, and asymmetric transfer hydrogenation of the enal with a chiral organocatalyst was conducted as a stereoinduction step. To measure the stereoinduction level and optical purity of the product, a convenient analytical method was developed in which a phenylcarbamate derivative of the C15 alcohol was found to be suitable to give proper polarity and UV-activity for chiral UV-HPLC analysis.

Meserine, a Novel Carbamate AChE Inhibitor, Ameliorates Scopolamine‐Induced Dementia and Alleviates Amyloidogenesis of APP/PS1 Transgenic Mice

To investigate whether Meserine, a novel phenylcarbamate derivative of (-)-meptazinol, possesses beneficial activities against cholinergic deficiency and amyloidogenesis, the two major pathological characteristics of Alzheimer's disease (AD). Ellman's assay and Morris water maze were used to detect acetylcholinesterase (AChE) activity and evaluate spatial learning and memory ability, respectively. Both high content screening and Western blotting were carried out to detect β-amyloid precursor protein (APP), while RT-PCR and ELISA were conducted to detect APP-mRNA and β-amyloid peptide (Aβ). In scopolamine-induced dementia mice, Meserine (1 mg/kg, i.p.) significantly ameliorated spatial learning and memory deficits, which was consistent with its in vitro inhibitory ability against AChE (recombinant human AChE, IC50 = 274 ± 49 nM). Furthermore, Meserine (7.5 mg/kg) injected intraperitoneally once daily for 3 weeks lowered APP level by 28% and Aβ42 level by 42% in APP/PS1 transgenic mouse cerebrum. This APP modulation action might be posttranscriptional, as Meserine reduced APP by about 30% in SH-SY5Y-APP695 cells but did not alter APP-mRNA level. And both APP and Aβ42 lowering action of Meserine maintained longer than that of rivastigmine. Meserine executes dual actions against cholinergic deficiency and amyloidogenesis and provides a promising lead compound for symptomatic and modifying therapy of AD.

Monoamine oxidase inhibitory activity of 3,5-biaryl-4,5-dihydro-1H-pyrazole-1-carboxylate derivatives

Ethyl and phenyl carbamate derivatives of pyrazoline (3a–3h) were synthesized and tested for their MAO inhibitory activity. All the compounds were found to be selective towards MAO-A. Phenyl carbamates (3e–3h) were better than ethyl carbamates (3a–3d) and displayed the best selectivity index. Compound 3f (KiMAO-A; 4.96 ± 0.21 nM) was found to be equally potent as that of standard drug, Moclobemide (KiMAO-A; 5.01 ± 0.13 nM) but with best selectivity index (8.86 × 10−5). Molecular docking studies with R &S conformer of 3f revealed S-enantiomer is better than R-enantiomer as reported earlier by other groups. It is proposed that VdW's radii of the substitution (bulkiness) in ring B determine the potency of phenyl carbamates.

Enantioseparation using ortho- or meta-substituted phenylcarbamates of amylose as chiral stationary phases for high-performance liquid chromatography

Six ortho- and six meta-substituted phenylcarbamate derivatives of amylose were prepared and their chiral recognition abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). The substitution at the meta-position on the aromatic ring was more preferable than that at the ortho-position to obtain CSPs with a high chiral recognition ability, and the introduction of either an electron-withdrawing or electron-donating substituent can improve the chiral resolving power of the meta-substituted phenylcarbamates of amylose. The chiral recognition ability of the amylose phenylcarbamates and elution order of the enantiomers were significantly dependent on the position, nature and number of the substituents on the phenyl group. Correlations between the chiral recognition ability and the N–H frequencies in the IR spectra and the chemical shifts of the N–H protons in the 1H NMR spectra of the carbamate moieties of the amylose derivatives were discussed. The structures of the amylose derivatives were also investigated by circular dichroism spectroscopy.

Convenient synthesis of some new pyrazolo[5,1-c]triazines, isoxazolo[3,4-d] pyrimidine and pyridine derivatives containing benzofuran moiety

Pyrazolo[5,1- c ][1,2,4]triazine, [1,2,4]triazolo[3,4- c ][1,2,4]triazine, benzo[4,5]-imidazo[2,1- c ][1,2,4]triazine, isoxazole, isoxazolo[3,4- d ]pyridazine, pyrazole, pyridine, substituted urea and phenyl carbamate derivatives containing benzofuran moiety were synthesized via reaction of sodium salt of 5-hydroxy-l-benzofuran-2-ylpropenone or 1-(benzofuran-2-yl)-3-(dimethylamino)prop-2-en-1-one with diazotized heterocyclic amines, hydroximoyl chlorides and active methylene compounds. The structures of all the newly synthesized compounds were confirmed by elemental analyses, spectral data, and alternative synthetic routes, whenever possible.

Study of the enantiomeric separation of an acetamide intermediate by using supercritical fluid chromatography and several polysaccharide based chiral stationary phases

Four chiral stationary phases, based on the phenylcarbamate derivatives of amylose or cellulose: Chiralcel OD-H, Chiralpak AD, Lux Cellulose-2 and Lux Amylose-2, were evaluated for the enantiomeric separation of an acetamide chiral intermediate, the (4S-trans)-4-(ethylamino)-4-(N-acetamide)-5,6-dihydro-(6S)-methyl-4H-thieno-[2,3-b]thiopyran-7,7-dioxide, using SFC. The effect of the different modifiers and temperatures, on the separation, was also studied. The chiral separation could not be achieved using the Chiralpak AD column, nevertheless the other columns provided excellent results with analysis times close to 6 min and resolutions higher than 2. The highest enantioresolutions and retentions were obtained with the Lux Cellulose-2 column and 2-propanol as organic modifier. The isoelution temperatures were estimated from the van’t Hoff plots, and in all the cases they were above the temperature range studied which means that the enantiomeric separation was enthalpy driven.

フェニルカルバメート化キチン・キトサンの合成と構造および置換度解析

フェニルカルバメート化キチン・キトサンの合成と構造および置換度解析

Chiral polymers for resolution of enantiomers

AbstractIn 1979, the formation of one‐handed helical poly(triphenylmethyl methacrylate) (PTrMA) was found through the helix‐sense‐selective polymerization of methacrylate using chiral anionic initiators, and the existence of a stable helical polymer without chiral side chains was proved. The chiral polymer exhibited unexpected high chiral recognition of various racemic compounds when used as the chiral packing material (CPM) for HPLC, which was commercialized in 1982 as the first chiral column based on an optically active polymer. This success encouraged us to develop further useful commercial chiral packing materials (CPMs) based on polysaccharides, cellulose, and amylose. By using these polysaccharide‐based CPMs, particularly phenylcarbamate derivatives, nearly 90% of chiral compounds can be resolved not only analytically but also preparatively, and several chiral drugs have been produced using the CPMs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1731–1739, 2009