Archives for Chemistry Experiments of 91-02-1

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Rowley, JA; Reid, RC; Poon, EKY; Wu, KC; Lim, JX; Lohman, RJ; Hamidon, JK; Yau, MK; Halili, MA; Durek, T; Iyer, A; Fairlie, DP or concate me.. SDS of cas: 91-02-1

I found the field of Pharmacology & Pharmacy very interesting. Saw the article Potent Thiophene Antagonists of Human Complement C3a Receptor with Anti-Inflammatory Activity published in 2020.0. SDS of cas: 91-02-1, Reprint Addresses Reid, RC; Fairlie, DP (corresponding author), Univ Queensland, Inst Mol Biosci, Div Chem & Struct Biol, Brisbane, Qld 4072, Australia.; Reid, RC; Fairlie, DP (corresponding author), Univ Queensland, Inst Mol Biosci, Australian Res Council, Ctr Excellence Adv Mol Imaging, Brisbane, Qld 4072, Australia.; Reid, RC; Fairlie, DP (corresponding author), Univ Queensland, Inst Mol Biosci, Ctr Inflammat & Dis Res, Brisbane, Qld 4072, Australia.. The CAS is 91-02-1. Through research, I have a further understanding and discovery of Phenyl(pyridin-2-yl)methanone

Structure-activity relationships for a series of small-molecule thiophenes resulted in potent and selective antagonism of human Complement C3a receptor. The compounds are about 100-fold more potent than the most reported antagonist SB290157. A new compound JR14a was among the most potent of the new antagonists in vitro, assessed by (a) inhibition of intracellular calcium release (IC50 10 nM) induced in human monocyte-derived macrophages by 100 nM C3a, (b) inhibition of beta-hexosaminidase secretion (IC50 8 nM) from human LAD2 mast cells degranulated by 100 nM C3a, and (c) selectivity for human C3aR over C5aR JR14a was metabolically stable in rat plasma and in rat liver microsomes and efficacious in rats when given orally to suppress rat paw inflammation, macrophage and mast cell activation, and histopathology induced by intraplantar paw administration of a C3aR agonist. Potent C3aR antagonists are now available for interrogating C3a receptor activation and suppressing C3aR-mediated inflammation in mammalian physiology and disease.

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Rowley, JA; Reid, RC; Poon, EKY; Wu, KC; Lim, JX; Lohman, RJ; Hamidon, JK; Yau, MK; Halili, MA; Durek, T; Iyer, A; Fairlie, DP or concate me.. SDS of cas: 91-02-1

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

Search for chemical structures by a sketch :91-02-1

Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Li, ZN; Wang, ZX; Wang, YH; Wu, XF; Lu, H; Huang, ZD; Chen, F or concate me.

Formula: C12H9NO. Recently I am researching about ACTIVE ALPHA-PHENYLPYRIDYLMETHANOLS; ARYL HETEROARYL KETONES; ENANTIOSELECTIVE REDUCTION; ASYMMETRIC-SYNTHESIS; KLUYVEROMYCES-MARXIANUS; BIOCATALYTIC SYNTHESIS; CARBONYL REDUCTASE; CELL-CULTURES; SUBSTRATE; BIOREDUCTION, Saw an article supported by the Shanghai Sailing Program [18YF1402100]. Published in WILEY-V C H VERLAG GMBH in WEINHEIM ,Authors: Li, ZN; Wang, ZX; Wang, YH; Wu, XF; Lu, H; Huang, ZD; Chen, F. The CAS is 91-02-1. Through research, I have a further understanding and discovery of Phenyl(pyridin-2-yl)methanone

We report here the discovery of a novel ketoreductase (KRED), named KmCR2, with a broad substrate spectrum on bioreduction of sterically bulky diaryl- and aryl(heteroaryl)methanones. The position of the substituent on aromatic rings (meta versus para or ortho) was revealed to control the stereospecificity of KmCR2. The stereoselective preparation of both enantiomers of diaryl- or aryl(heteroaryl)methanols using strategically engineered substrates with a traceless directing group (bromo group) showcased the potential application of this substrate-controlled bioreduction reaction. The combined use of substrate engineering and protein engineering, was demonstrated to be a useful strategy in efficiently improving stereoselectivity or switching stereopreference of enzymatic processes.

Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Li, ZN; Wang, ZX; Wang, YH; Wu, XF; Lu, H; Huang, ZD; Chen, F or concate me.

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

When did you first realize you had a special interest and talent in3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride

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.

HPLC of Formula: C8H10ClNO3. I found the field of Chemistry very interesting. Saw the article A novel diarylethene probe with high selective recognition of CN- and Mg2+ and its application published in 2020.0, Reprint Addresses Li, H; Pu, SZ (corresponding author), Jiangxi Sci & Technol Normal Univ, Jiangxi Key Lab Organ Chem, Nanchang 330013, Jiangxi, Peoples R China.. The CAS is 65-22-5. Through research, I have a further understanding and discovery of 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride.

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

The Shocking Revelation of Ethyl nicotinate

About Ethyl nicotinate, If you have any questions, you can contact Lima, F; Meisenbach, M; Schenkel, B; Sedelmeier, J or concate me.. Product Details of 614-18-6

Category: pyridine-derivatives. Authors Lima, F; Meisenbach, M; Schenkel, B; Sedelmeier, J in ROYAL SOC CHEMISTRY published article about in [Lima, Fabio] Novartis Pharma AG, Novartis Inst Biomed Res, Global Discovery Chem, Basel, Switzerland; [Lima, Fabio; Meisenbach, Mark; Schenkel, Berthold; Sedelmeier, Joerg] Novartis Pharma AG, Chem & Analyt Dev, Basel, Switzerland; [Sedelmeier, Joerg] F Hoffmann La Roche Ltd, Small Mol Tech Dev, Basel, Switzerland in 2021, Cited 46. The Name is Ethyl nicotinate. Through research, I have a further understanding and discovery of 614-18-6

We herein report two complementary strategies employing organolithium chemistry for the synthesis of glyoxal derivatives. Micro-mixer technology allows for the generation of unstable organometallic intermediates and their instantaneous in-line quenching with esters as electrophiles. Selective mono-addition was observed via putative stabilized tetrahedral intermediates. Advantages offered by flow chemistry technologies facilitate direct and efficient access to masked 1,2-dicarbonyl compounds while mitigating undesired by-product formation. These two approaches enable the production of advanced and valuable synthetic building blocks for heterocyclic chemistry with throughputs of grams per minute.

About Ethyl nicotinate, If you have any questions, you can contact Lima, F; Meisenbach, M; Schenkel, B; Sedelmeier, J or concate me.. Product Details of 614-18-6

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

Discovery of 614-18-6

About Ethyl nicotinate, If you have any questions, you can contact Fairley, M; Bole, LJ; Mulks, FF; Main, L; Kennedy, AR; O’Hara, CT; Garcia-Alvarez, J; Hevia, E or concate me.. HPLC of Formula: C8H9NO2

Fairley, M; Bole, LJ; Mulks, FF; Main, L; Kennedy, AR; O’Hara, CT; Garcia-Alvarez, J; Hevia, E in [Fairley, Michael; Mulks, Florian F.; Main, Laura; Kennedy, Alan R.; O’Hara, Charles T.; Hevia, Eva] Univ Strathclyde, Dept Pure & Appl Chem, Glasgow G1 1XL, Lanark, Scotland; [Bole, Leonie J.; Mulks, Florian F.; Hevia, Eva] Univ Bern, Dept Chem & Biochem, CH-3012 Bern, Switzerland; [Garcia-Alvarez, Joaquin] Univ Oviedo, Lab Compuestos Organomet & Catalisis, Ctr Innovac Quim Avanzada ORFEO CINQA, Dept Quim Organ & Inorgan IUQOEM,Fac Quim,Unidad, E-33071 Oviedo, Spain published Ultrafast amidation of esters using lithium amides under aerobic ambient temperature conditions in sustainable solvents in 2020, Cited 97. Category: pyridine-derivatives. The Name is Ethyl nicotinate. Through research, I have a further understanding and discovery of 614-18-6.

Lithium amides constitute one of the most commonly used classes of reagents in synthetic chemistry. However, despite having many applications, their use is handicapped by the requirement of low temperatures, in order to control their reactivity, as well as the need for dry organic solvents and protective inert atmosphere protocols to prevent their fast decomposition. Advancing the development of air- and moisture-compatible polar organometallic chemistry, the chemoselective and ultrafast amidation of esters mediated by lithium amides is reported. Establishing a novel sustainable access to carboxamides, this has been accomplishedviadirect C-O bond cleavage of a range of esters using glycerol or 2-MeTHF as a solvent, in air. High yields and good selectivity are observed while operating at ambient temperature, without the need for transition-metal mediation, and the protocol extends to transamidation processes. Pre-coordination of the organic substrate to the reactive lithium amide as a key step in the amidation processes has been assessed, enabling the structural elucidation of the coordination adduct [{Li(NPh2)(O=CPh(NMe2))}(2)] (8) when toluene is employed as a solvent. No evidence for formation of a complex of this type has been found when using donor THF as a solvent. Structural and spectroscopic insights into the constitution of selected lithium amides in 2-MeTHF are provided that support the involvement of small kinetically activated aggregates that can react rapidly with the organic substrates, favouring the C-O bond cleavage/C-N bond formation processes over competing hydrolysis/degradation of the lithium amides by moisture or air.

About Ethyl nicotinate, If you have any questions, you can contact Fairley, M; Bole, LJ; Mulks, FF; Main, L; Kennedy, AR; O’Hara, CT; Garcia-Alvarez, J; Hevia, E or concate me.. HPLC of Formula: C8H9NO2

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

Archives for Chemistry Experiments of C12H9NO

HPLC of Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Mangalam, NA; Kurup, MRP; Suresh, E; Kaya, S; Serdaro, G or concate me.

HPLC of Formula: C12H9NO. Authors Mangalam, NA; Kurup, MRP; Suresh, E; Kaya, S; Serdaro, G in ELSEVIER published article about in [Mangalam, Neema Ani; Kurup, M. R. Prathapachandra] Cochin Univ Sci & Technol, Dept Appl Chem, Kochi 682022, Kerala, India; [Mangalam, Neema Ani] Mar Thoma Coll, Dept Chem, Tiruvalla 689103, Kerala, India; [Kurup, M. R. Prathapachandra] Cent Univ Kerala, Sch Phys Sci, Dept Chem, Tejaswini Hills, Kasaragod 671320, Kerala, India; [Suresh, Eringathodi] Cent Salt & Marine Chem Res Inst, Analyt Sci Discipline, Bhavnagar 364002, Gujarat, India; [Kaya, Savas] Sivas Cumhuriyet Univ, Hlth Serv Vocat Sch, Dept Pharm, TR-58140 Sivas, Turkey; [Serdaro, Goncagul] Sivas Cumhuriyet Univ, Math & Sci Edu, TR-58140 Sivas, Turkey in 2021.0, Cited 53.0. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1

Five cobalt complexes synthesized from two aroylhydrazones were characterized by elemental analyses, thermogravimetric analysis, molar conductivity, magnetic susceptibility measurements, IR and electronic spectra. Single crystal X-ray structure of one of the complex is also reported and it got crystallized in triclinic space group P (1) over bar and the crystal structure shows a distorted octahedral geometry around the metal center. Spectral data reveal that both the aroylhydrazones are tridentate and coordinate through the azomethine nitrogen, hydrazonic oxygen, and pyridyl nitrogen. Magnetic susceptibility measurements confirm the paramagnetic nature of the Co(II) complexes and one of the complex was found to be diamagnetic in nature. Additionally, HF/6-311G(d,p)/LANL2DZ calculations were performed to predict the possible intramolecular interactions contributing to the lowering of the stabilization energy. Accordingly, pi -> pi* transitions were found to be responsible for the stabilization energy for the ligands and their cobalt complexes. To describe and discuss the chemical reactivity and stability of synthesized complexes, quantum chemical parameters like frontier orbital energies, hardness, softness, energy gap, electronegativity, chemical potential, electrophilicity, polarizability and dipole moment were calculated. Also, the main electronic structure principles such as maximum hardness, minimum polarizability, and minimum electrophilicity principles were considered to evaluate the stability of the complexes. (C) 2021 Elsevier B.V. All rights reserved.

HPLC of Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Mangalam, NA; Kurup, MRP; Suresh, E; Kaya, S; Serdaro, G or concate me.

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

Extracurricular laboratory: Synthetic route of 91-02-1

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Palav, A; Misal, B; Ganwir, P; Badani, P; Chaturbhuj, G or concate me.. Computed Properties of C12H9NO

Recommanded Product: 91-02-1. Recently I am researching about SELECTIVE OXIDATION; N-BROMOSUCCINIMIDE; SULFATED POLYBORATE; BENZYLIC ALCOHOLS; EFFICIENT; CATALYST; ALDEHYDES; COMPLEX; DERIVATIVES; WATER, Saw an article supported by the Department of Science and Technology, India (WOS-A)Department of Science & Technology (India)Department of Science & Technology (DOST), Philippines; Loba Chemie Pvt. Ltd.. Published in PERGAMON-ELSEVIER SCIENCE LTD in OXFORD ,Authors: Palav, A; Misal, B; Ganwir, P; Badani, P; Chaturbhuj, G. The CAS is 91-02-1. Through research, I have a further understanding and discovery of Phenyl(pyridin-2-yl)methanone

Chlorine is the 20th most abundant element on the earth compared to bromine, iodine, and fluorine, a sulfonimide reagent, N-chloro-N-(phenylsulfonyl)benzenesulfonamide (NCBSI) was identified as a mild and selective oxidant. Without activation, the reagent was proved to oxidize primary and secondary alcohols as well as their symmetrical and mixed ethers to corresponding aldehydes and ketones. With recoverable PS-TEMPO catalyst, selective oxidation over chlorination of primary and secondary alcohols and their ethers with electron-donating substituents was achieved. The reagent precursor of NCBSI was recovered quantitatively and can be reused for synthesizing NCBSI. (C) 2021 Elsevier Ltd. All rights reserved.

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Palav, A; Misal, B; Ganwir, P; Badani, P; Chaturbhuj, G or concate me.. Computed Properties of C12H9NO

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

Brief introduction of 65-22-5

About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Song, Z; Liu, J; Hou, YX; Yuan, W; Yang, BS or concate me.. Recommanded Product: 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride

In 2019.0 SPECTROCHIM ACTA A published article about HUMAN SERUM-ALBUMIN; METAL-IONS; PSEUDOMONAS-SYRINGAE; SECONDARY STRUCTURE; COPPER PROTEINS; BINDING; STABILITY; ITC; METALLOCHAPERONES; THERMODYNAMICS in [Song, Zhen; Hou, Yuxin; Yuan, Wen] Taiyuan Normal Univ, Dept Chem, Jinzhong 030619, Peoples R China; [Yang, Binsheng] Shanxi Univ, Key Lab Chem Biol & Mol Engn, Minist Educ, Inst Mol Sci, Taiyuan 030006, Shanxi, Peoples R China; [Liu, Jin] Chinese Peoples Armed Police Forces, Hubei Prov Corps Hosp, Wuhan 430061, Hubei, Peoples R China in 2019.0, Cited 38.0. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5. COA of Formula: C8H10ClNO3

The interaction between pyridoxal hydrochloride (HQ) and apoCopC was investigated using Fourier transform infrared spectroscopy (FTIR), isothermal titration calorimetry (ITC), circular dichroism (CD), fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy, fluorescence lifetime, TNS fluorescence and docking methods. FTIR, CD, TNS fluorescence and fluorescence lifetime experiments suggested that the apoCopC conformation was altered by HQ with an increase in the random coil content and a reduction in the beta-sheet content. In addition, the data from fluorescence spectroscopy, 3D fluorescence spectroscopy and molecular docking revealed that the binding site of HQ was located in the hydrophobic area of apoCopC, and a redshift of the HQ fluorescence spectra was observed. Furthermore, ITC and fluorescence quenching data manifested that the binding ratio of HQ and apoCopC was 1:1, and the forming constant was calculated to be (7.06 +/- 0.21) x 10(5) M-1. The thermodynamic parameters Delta H and Delta S suggested that the formation of a CopC-HQcomplex depended on the hydrophobic force. Furthermore, the average binding distance between tryptophan in apoCopC and HQ was determined by means of Forster non-radioactive resonance energy transfer and molecular docking. The results agreed well with each other. As a redox switch in the modulation of copper, the interaction of apoCopC with small molecules will affect the action of the redox switch. These findings could provide useful information to illustrate the copper regulation mechanism. (C) 2018 Elsevier B.V. All rights reserved.

About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Song, Z; Liu, J; Hou, YX; Yuan, W; Yang, BS or concate me.. Recommanded Product: 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride

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

An update on the compound challenge: 91-02-1

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Wang, SD; Huang, HY; Tsareva, S; Bruneau, C; Fischmeister, C or concate me.. Recommanded Product: Phenyl(pyridin-2-yl)methanone

Recently I am researching about SELECTIVE HYDROGENATION; HOMOGENEOUS CATALYSIS; CARBONYL DERIVATIVES; EFFICIENT SYNTHESIS; CONVERSION; RUTHENIUM; BIOMASS, Saw an article supported by the China Scholarship CouncilChina Scholarship Council. Published in WILEY-V C H VERLAG GMBH in WEINHEIM ,Authors: Wang, SD; Huang, HY; Tsareva, S; Bruneau, C; Fischmeister, C. The CAS is 91-02-1. Through research, I have a further understanding and discovery of Phenyl(pyridin-2-yl)methanone. Product Details of 91-02-1

The silver-catalyzed hydrogenation of ketones using H-2 as hydrogen source is reported. Silver nanoparticles are generated from simple silver (I) salts and operate at 25 degrees C under 20 bar of hydrogen pressure. Various aliphatic and aromatic ketones, including natural products were reduced into the corresponding alcohols in high yields. This silver catalyst allows for the selective hydrogenation of ketones in the presence of other functional groups.

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Wang, SD; Huang, HY; Tsareva, S; Bruneau, C; Fischmeister, C or concate me.. Recommanded Product: Phenyl(pyridin-2-yl)methanone

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

What advice would you give a new faculty member or graduate student interested in a career 91-02-1

Application In Synthesis of Phenyl(pyridin-2-yl)methanone. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Kim, JH; Ofori, S; Parkin, S; Vekaria, H; Sullivan, PG; Awuah, SG or concate me.

Authors Kim, JH; Ofori, S; Parkin, S; Vekaria, H; Sullivan, PG; Awuah, SG in ROYAL SOC CHEMISTRY published article about in [Kim, Jong Hyun; Ofori, Samuel; Parkin, Sean; Awuah, Samuel G.] Univ Kentucky, Dept Chem, Lexington, KY 40506 USA; [Awuah, Samuel G.] Univ Kentucky, Coll Pharm, Ctr Pharmaceut Res & Innovat, Lexington, KY 40536 USA; [Awuah, Samuel G.] Univ Kentucky, Coll Pharm, Dept Pharmaceut Sci, Lexington, KY 40536 USA; [Vekaria, Hemendra; Sullivan, Patrick G.] Univ Kentucky, Spinal Cord & Brain Injury Res Ctr, Lexington, KY USA; [Sullivan, Patrick G.] Univ Kentucky, Dept Neurosci, Lexington, KY USA; [Sullivan, Patrick G.] Lexington Vet Affairs Healthcare Syst, Lexington, KY USA in 2021.0, Cited 75.0. Application In Synthesis 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

Expanding the chemical diversity of metal complexes provides a robust platform to generate functional bioactive reagents. To access an excellent repository of metal-based compounds for probe/drug discovery, we capitalized on the rich chemistry of gold to create organometallic gold(III) compounds by ligand tuning. We obtained novel organogold(III) compounds bearing a 1,2-bis(diphenylphosphino)benzene ligand, providing structural diversity with optimal physiological stability. Biological evaluation of the lead compound AuPhos-89 demonstrates mitochondrial complex I-mediated alteration of the mitochondrial electron transport chain (ETC) to drive respiration and diminish cellular energy in the form of adenosine triphosphate (ATP). Mechanism-of-action efforts, RNA-Seq, quantitative proteomics, and NCI-60 screening reveal a highly potent anticancer agent that modulates mitochondrial ETC. AuPhos-89 inhibits the tumor growth of metastatic triple negative breast cancer and represents a new strategy to study the modulation of mitochondrial respiration for the treatment of aggressive cancer and other disease states where mitochondria play a pivotal role in the pathobiology.

Application In Synthesis of Phenyl(pyridin-2-yl)methanone. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Kim, JH; Ofori, S; Parkin, S; Vekaria, H; Sullivan, PG; Awuah, SG or concate me.

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