Pyridine-derivatives

In 2019.0 CHEMELECTROCHEM published article about C-H FUNCTIONALIZATION; CATALYZED TRANSANNULATION; EFFICIENT SYNTHESIS; COUPLING REACTIONS; PYRIDOTRIAZOLES; METAL; STRATEGIES; HYDRAZONES; OXIDATION; PYRIDINES in [Xu, Pin; Xu, Hai-Chao] Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Coll Chem & Chem Engn, Xiamen 361005, Fujian, Peoples R China in 2019.0, Cited 61.0. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1. Computed Properties of C12H9NO

The synthesis of [1,2,3]triazolo[1,5-a]pyridines through electrochemical dehydrogenative cyclization of hydrazones of 2-acylpyridines is presented. The reactions are carried out under mild conditions without oxidizing reagents or transition-metal catalysts.

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Xu, P; Xu, HC or concate me.. Computed Properties of C12H9NO

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

An article Antimicrobial and antitumor activity of S-methyl dithiocarbazate Schiff base zinc(II) complexes WOS:000667427600006 published article about X-RAY-STRUCTURE; METAL-COMPLEXES; BIOLOGICAL EVALUATION; CRYSTAL-STRUCTURE; DNA-BINDING; METHYLDITHIOCARBAZATE SMDTC; ANTIBACTERIAL ACTIVITY; ANTIFUNGAL ACTIVITY; CIRCULAR-DICHROISM; ZN(II) COMPLEXES in [Ramilo-Gomes, Filipa; Addis, Yemataw; Tekamo, Israel; Cavaco, Isabel; Matilde Marques, M.; Pessoa, Joao Costa; Correia, Isabel] Univ Lisbon, Inst Super Tecn, Ctr Quim Estrutural, Av Rovisco Pais, P-1049001 Lisbon, Portugal; [Ramilo-Gomes, Filipa; Addis, Yemataw; Tekamo, Israel; Cavaco, Isabel; Matilde Marques, M.; Pessoa, Joao Costa; Correia, Isabel] Univ Lisbon, Inst Super Tecn, Dept Engn Quim, Av Rovisco Pais, P-1049001 Lisbon, Portugal; [Ramilo-Gomes, Filipa] Univ Lisbon, Inst Invest Medicamento IMed ULisboa, Fac Farm, Av Prof Gama Pinto, P-1649003 Lisbon, Portugal; [Addis, Yemataw; Tekamo, Israel; Cavaco, Isabel] Univ Algarve, Dept Quim & Farm, Campus Gambelas, P-8005139 Faro, Portugal; [Campos, Debora L.; Pavan, Fernando R.] UNESP, Fac Ciencias Farmaceut, CP 582, BR-14801902 Araraquara, SP, Brazil; [Gomes, Clara S. B.] Univ NOVA Lisboa, Dept Quim, LAQV REQUIMTE Lab Associado Quim Verde, Fac Ciencias & Tecnol, P-2829516 Monte De Caparica, Portugal; [Gomes, Clara S. B.] Univ NOVA Lisboa, Appl Mol Biosci Unit UCIBIO, Fac Ciencias & Tecnol, P-2829516 Monte De Caparica, Portugal; [Brito, Vanessa; Santos, Adriana O.; Domingues, Fernanda; Luis, Angelo; Ferreira, Susana; Silvestre, Samuel] Univ Beira Interior, CICS UBI Hlth Sci Res Ctr, Av Infante D Henrique, P-6200506 Covilha, Portugal in 2021.0, Cited 80.0. Quality Control of 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5

Schiff bases (SB) obtained from S-methyl dithiocarbazate and aromatic aldehydes: salicylaldehyde (H2L1), ovanillin (H2L2), pyridoxal (H2L3) and 2,6-diformyl-4-methylphenol (H3L4), and their corresponding Zn(II)complexes (1-4), are synthesized. All compounds are characterized by elemental analyses, infrared, UV-Vis, nuclear magnetic resonance spectroscopy and mass spectrometry. The structures of H2L2 and [Zn-2(L-1)(2)(H2O) (DMF)] (1a) (DMF = dimethylformamide) are solved by single crystal X-ray diffraction. The SB coordinates the metal center through the Ophenolate, Nimine and Sthiolate atoms. The radical scavenging activity is tested using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with all ligand precursors showing IC50 values similar to 40 mu M. Cytotoxicity studies with several tumor cell lines (PC-3, MCF-7 and Caco-2) as well as a non-tumoral cell line (NHDF) are reported. Interestingly, 1 has relevant and selective antiproliferative effect against Caco-2 cells (IC50 = 9.1 mu M). Their antimicrobial activity is evaluated in five bacterial strains (Klebsiella pneumoniae, Acinetobacter baumannii, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus) and two yeast strains (Candida albicans and Candida tropicalis) with some compounds showing bacteriostatic and fungicidal activity. The minimal inhibitory concentration (MIC90) of HnL against Mycobacterium tuberculosis is also reported, with H2L2 and H3L4 showing very high activity (MIC90 < 0.6 mu g/mL). The ability of the compounds to bind bovine serum albumin (BSA) and DNA is evaluated for H3L4 and [Zn-2(L-4)(CH3COO)] (4), both showing high binding constants to BSA (ca. 106 M 1) and ability to bind DNA. Overall, the reported compounds show relevant antitumor and antimicrobial properties, our data indicating they may be promising compounds in several fields of medicinal chemistry. Quality Control of 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Ramilo-Gomes, F; Addis, Y; Tekamo, I; Cavaco, I; Campos, DL; Pavan, FR; Gomes, CSB; Brito, V; Santos, AO; Domingues, F; Luis, A; Marques, MM; Pessoa, JC; Ferreira, S; Silvestre, S; Correia, I or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Authors Oguro, Y; Nakamura, A; Kurahashi, A in SOC BIOSCIENCE BIOENGINEERING JAPAN published article about THERMAL-STABILITY; ACID; PH in [Oguro, Yoshifumi; Nakamura, Ayana; Kurahashi, Atsushi] Hakkaisan Brewery Co Ltd, 1051 Nagamori, Minamiuonuma, Niigata 9497112, Japan in 2019.0, Cited 22.0. Category: pyridine-derivatives. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5

Koji amazake, prepared from rice koji, is a traditional Japanese sweet beverage. The main source of sweetness is glucose derived from rice starch following digestion by enzymes of Aspergillus oryzae during saccharification. The temperature of this process was empirically determined as 45 degrees C-60 degrees C, but no studies have systematically investigated the effect of temperature on saccharification efficiency. We addressed this in the present study by evaluating saccharification efficiency at various temperatures. We found that glucose content was the highest at 50 degrees C (100%) and was reduced at temperatures of 40 degrees C (66.4%), 60 degrees C (91.9%), and 70 degrees C (76.6%). We previously reported that 12 types of oligosaccharides are present in koji amazake; the levels of eight of these, namely nigerose, kojibiose, trehalose, isomaltose, gentiobiose, raffinose, panose, and isomaltotriose, were the highest at 50 degrees C-60 degrees C, whereas sophorose production was maximal at 70 degrees C. Based on these findings, we initially performed saccharification at 50 degrees C and then switched the temperature to 70 degrees C. The maximum amount of each saccharide including sophorose that was produced was close to the values obtained at these two temperatures. Thus, oligosaccharide composition of koji amazake is dependent on saccharification temperature. These findings provide useful information for improving the consumer appeal of koji amazake by enhancing oligosaccharide content. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.

About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Oguro, Y; Nakamura, A; Kurahashi, A or concate me.. Category: pyridine-derivatives

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

HPLC of Formula: C8H10ClNO3. Authors Pishchugin, FV; Tuleberdiev, IT in MAIK NAUKA/INTERPERIODICA/SPRINGER published article about in [Pishchugin, F. V.; Tuleberdiev, I. T.] Kyrgyz Natl Acad Sci, Inst Chem & Phytotechnol, Bishkek 720071, Kyrgyzstan in 2021.0, Cited 13.0. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5

The kinetics and mechanism of condensation of pyridoxal hydrochloride with L-alpha-asparagine, L-alpha- and D-alpha-aspartic acids are analyzed via UV spectroscopy and polarimetry. It is found that L-alpha-asparagine containing alpha-NH2 and gamma-NH2 groups interacts with pyridoxal via the gamma-NH2 group, forming Schiff bases that are resistant to chemical transformations. Rearrangement produces Schiff bases that form the cyclic structure from the amino acid moiety. L-alpha- and D-alpha-aspartic acids interacting with pyridoxal via alpha-NH2 groups create Schiff bases that form quinoid structures after elimination of alpha-hydrogen or CO2. Their subsequent hydrolysis results in pyridoxamine, alpha-ketoacids, and aldehyde acids, respectively. Schemes of the condensation mechanisms of L-alpha-asparagine, L-alpha-, D-alpha-aspartic acids with pyridoxal hydrochloride are proposed.

HPLC of Formula: C8H10ClNO3. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Pishchugin, FV; Tuleberdiev, IT or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

An article Copper-Catalyzed Asymmetric Radical 1,2-Carboalkynylation of Alkenes with Alkyl Halides and Terminal Alkynes WOS:000537415600047 published article about CROSS-COUPLING REACTIONS; ENANTIOSELECTIVE 1,2-DIFUNCTIONALIZATION; IODIDES; TRIFLUOROMETHYLATION; FUNCTIONALIZATION; 1,2-ADDITION; ALKYNYLATION; STRATEGY; DIENES; LIGAND in [Dong, Xiao-Yang] Harbin Inst Technol, Sch Chem & Chem Engn, Harbin 150001, Peoples R China; [Dong, Xiao-Yang; Cheng, Jiang-Tao; Zhang, Yu-Feng; Zhan, Tian-Ya; Chen, Ji-Jun; Wang, Fu-Li; Yang, Ning-Yuan; Liu, Xin-Yuan] Southern Univ Sci & Technol, Shenzhen Grubbs Inst, Shenzhen 518055, Peoples R China; [Dong, Xiao-Yang; Cheng, Jiang-Tao; Zhang, Yu-Feng; Zhan, Tian-Ya; Chen, Ji-Jun; Wang, Fu-Li; Yang, Ning-Yuan; Liu, Xin-Yuan] Southern Univ Sci & Technol, Dept Chem, Guangdong Prov Key Lab Catalysis, Shenzhen 518055, Peoples R China; [Li, Zhong-Liang; Ye, Liu; Gu, Qiang-Shuai] Southern Univ Sci & Technol, Acad Adv Interdisciplinary Studies, Shenzhen 518055, Peoples R China; [Li, Zhong-Liang; Ye, Liu; Gu, Qiang-Shuai] Southern Univ Sci & Technol, Dept Chem, Shenzhen 518055, Peoples R China in 2020.0, Cited 73.0. COA of Formula: C6H5NO. The Name is 3-Pyridinecarboxaldehyde. Through research, I have a further understanding and discovery of 500-22-1

A copper-catalyzed intermolecular three-component asymmetric radical 1,2-carboalkynylation of alkenes has been developed, providing straightforward access to diverse chiral alkynes from readily available alkyl halides and terminal alkynes. The utilization of a cinchona alkaloid-derived multidentate N,N,P-ligand is crucial for the efficient radical generation from mildly oxidative precursors by copper and the effective inhibition of the undesired Glaser coupling side reaction. The substrate scope is broad, covering (hetero)aryl-, alkynyl-, and aminocarbonyl-substituted alkenes, (hetero)aryl and alkyl as well as silyl alkynes, and tertiary to primary alkyl radical precursors with excellent functional group compatibility. Facile transformations of the obtained chiral alkynes have also been demonstrated, highlighting the excellent complementarity of this protocol to direct 1,2-dicarbofunctionalization reactions with C(sp(2)/sp(3))-based reagents.

COA of Formula: C6H5NO. About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Dong, XY; Cheng, JT; Zhang, YF; Li, ZL; Zhan, TY; Chen, JJ; Wang, FL; Yang, NY; Ye, L; Gu, QS; Liu, XY or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Recently I am researching about DUAL-CHANNEL RECOGNITION; MOLECULAR LOGIC GATES; TURN-ON SENSOR; FLUORESCENT SENSOR; AQUEOUS-MEDIA; COLORIMETRIC SENSOR; SCHIFF-BASE; CYANIDE; CHEMOSENSOR; MAGNESIUM, Saw an article supported by the National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [41867053]; Nanchang normal university Doctoral Research Startup fund [NSBSJJ2015035]; Open Project Program of 311 high level engineering center Jiangxi Science &Technology Normal University [KFGJ19004]. Published in ELSEVIER SCIENCE SA in LAUSANNE ,Authors: Yuwen, ZY; Mei, HX; Li, H; Pu, SZ. The CAS is 65-22-5. Through research, I have a further understanding and discovery of 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. HPLC of Formula: C8H10ClNO3

A chemical sensor composed of pyridoxal hydrochloride schiff base based on diarylethene (1O) was synthesized. Its photochemical properties and selectivity to ions were further studied. The chemosensor could detect cyanide effectively and is almost undisturbed by other ions. When titrating CN-, the reaction aroused a distinct change in the absorption spectrum with the color change from transparent to yellow, and the fluorescence intensity centered at 562 nm was increased 68 folds. It also exhibited a good fluorescence sensing of Mg(2+ )with high selectivity and sensitivity. Upon addition of Mg2+, its emission intensity enhanced 110 folds, with the color change from dark to bright blue. Its good spectral response could be applied to molecular logic circuit. Moreover, the chemosensor could be made into test paper strips for the qualitative and quantitative detection of CN- and Mg2+.

HPLC of Formula: C8H10ClNO3. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Yuwen, ZY; Mei, HX; Li, H; Pu, SZ or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

In 2020.0 POLYHEDRON published article about CYCLOHEXENE OXIDE; HIGHLY EFFICIENT; METAL-CATALYSTS; COPOLYMERIZATION; CO2; EPOXIDES in [Hwang, Saem; Ryu, Ji Yeon; Jung, Sung Hoo; Park, Hyoung-Ryun; Lee, Junseong] Chonnam Natl Univ, Dept Chem, 300 Yongbong Dong, Gwangju 500757, South Korea in 2020.0, Cited 33.0. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5. Recommanded Product: 65-22-5

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co (III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr(2)en = (N,N’-bis (pyridoxylideneiminato)ethylene) and pyr(2)cy = (N,N’-bis(pyridoxylideneiminato)cyclohexane)) and Co (OAc)(2) and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr(2)en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts. (C) 2020 Elsevier Ltd. All rights reserved.

Recommanded Product: 65-22-5. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Hwang, S; Ryu, JY; Jung, SH; Park, HR; Lee, J or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Authors Chatterjee, A; Kaur, G; Joshi, M; Choudhury, AR; Ghosh, R in ELSEVIER SCIENCE SA published article about COPPER(II) COMPLEXES; DICOPPER(II) COMPLEXES; PERCHLORATE REDUCTION; MAGNETIC-PROPERTIES; OXIDASE; LIGAND; DINUCLEAR; MODELS; SERIES in [Chatterjee, Arnab; Ghosh, Rajarshi] Univ Burdwan, Dept Chem, Burdwan 713104, W Bengal, India; [Kaur, Gurpreet; Joshi, Mayank; Choudhury, Angshuman Roy] Indian Inst Sci Educ & Res Mohali, Dept Chem Sci, Manauli 140306, India in 2020.0, Cited 29.0. Safety of Phenyl(pyridin-2-yl)methanone. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1

Two mononuclear Fe(II) complexes having same ligand framework, coordination geometry but different counter anions [Fe(L)]X-2 [L = N-(phenyl-pyridin-2-yl-methylene)-ethane-1,2-diamine; X = ClO4- (1), PF6- (2)] have been synthesized and crystallographically characterized. Both the complexes catalyzed catechol-quinone oxidation pH dependently. In the pH range 8.3-8.5 the suitable activity of both the complexes were found. Counter anions in the complexes played a significant role in controlling the turn over numbers of the catalytic reactions. In acetonitrile (MeCN), the turn over number for 1 was 4.99 h(-1) and for 2, it was 42.75 h(-1).

Safety of Phenyl(pyridin-2-yl)methanone. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Chatterjee, A; Kaur, G; Joshi, M; Choudhury, AR; Ghosh, R or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

An article Pd-Catalyzed CO/Vinyl Arene Copolymerization: when the Stereochemistry is Controlled by the Comonomer WOS:000575432700017 published article about ETHYLENE/METHYL ACRYLATE COOLIGOMERIZATION; CARBON-MONOXIDE; ALTERNATING COPOLYMERIZATION; CO/STYRENE COPOLYMERIZATION; PALLADIUM CATALYSTS; PD(II) CATALYSTS; COMPLEXES; DIIMINE; LIGANDS; OLEFINS in [Dall’Anese, Anna; Fiorindo, Mattia; Balducci, Gabriele; Alessio, Enzo; Milani, Barbara] Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy; [Olivieri, Diego; Carfagna, Carla] Univ Bologna, Dept Ind Chem Toso Montana, I-40136 Bologna, Italy; [Durand, Jerome] Univ Toulouse, Lab Chim Coordinat UPR CNRS 8241, Composante ENSIACET, F-31030 Toulouse, France in 2020.0, Cited 55.0. Quality Control of Phenyl(pyridin-2-yl)methanone. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1

The control of the stereochemistry of macromolecules is a very important goal, and coordination-insertion polymerization is superior with respect to the other polymerization methods for its achievement. In this contribution, we focus on Pd(II) homogeneous catalysts for the stereocontrolled synthesis of CO/vinyl arene polyketones. We developed a library of aldo- and keto-iminopyridine ligands N-N’ that feature an alpha- or beta-naphthyl or anthracenyl moiety on the imino nitrogen atom (N-imm). With such ligands, the Pd(II) monocationic complexes [Pd(CH3)(CH3CN)(N-N’)][PF6] were synthesized. NMR spectroscopy shows that in solution, each complex exists as an equilibrium mixture of cis and trans stereoisomers, the latter having the CH3 ligand opposite to the Pd-N-imm bond. The isomeric population depends on the N-N’ ligand: an almost 1:1 ratio is found for the ketimine complexes, whereas those with the aldimines show a preference for the trans geometry. These complexes generate very efficient catalysts for the CO/vinyl arene copolymerization. Catalyst performances depend both on the nature of N-N’ and of the vinyl arene comonomer. The ketimine-based catalysts are more stable and more productive than the aldimine counterpart, leading to prevailingly syndiotactic macromolecules of high M-w (up to 280 kDa). The aldimine derivatives produce copolymers with isotactic and syndiotactic stereoblocks of different lengths depending on the vinyl arene. The effect of the prochiral monomer on the copolymer tacticity is steric in nature as demonstrated by the stereochemistry of the obtained CO/4-fluorostyrene polyketone, whose synthesis is reported here for the first time. As a conclusion, we have now demonstrated that when catalysts with nonsymmetric ancillary ligands are used, and stereoisomers are present, the stereochemistry of the copolymerization is driven by both the catalyst isomeric distribution and the prochiral comonomer.

Quality Control of Phenyl(pyridin-2-yl)methanone. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Dall’Anese, A; Fiorindo, M; Olivieri, D; Carfagna, C; Balducci, G; Alessio, E; Durand, J; Milani, B or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Recommanded Product: 3-Pyridinecarboxaldehyde. I found the field of Chemistry very interesting. Saw the article One-Pot Reaction between N-Tosylhydrazones and 2-Nitrobenzyl Bromide: Route to NH-Free C2-Arylindoles published in 2019, Reprint Addresses Alami, M; Hamze, A (corresponding author), Univ Paris Sud, Fac Pharm, CNRS, LabEx LERMIT,Lab Chim Therapeut,BioCIS UMR 8076, Rue JB Clement, F-92296 Chatenay Malabry, France.. The CAS is 500-22-1. Through research, I have a further understanding and discovery of 3-Pyridinecarboxaldehyde.

A one-pot Barluenga coupling between N-tosylhydrazones and nitro-benzyl bromide, followed by deoxygenation of ortho-nitrostyrenes, and subsequent cyclization has been developed, providing a new way to synthesize various C2-arylindoles. This method exhibits a good substrate scope and functional group tolerance, and it allows an access to NH-free indoles, which can present a potential utility in medicinal chemistry applications.

About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Bzeih, T; Zhang, KN; Khalaf, A; Hachem, A; Alami, M; Hamze, A or concate me.. Recommanded Product: 3-Pyridinecarboxaldehyde

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem