Pyrazines

An article Discovery ofN-(1-(3-fluorobenzoyl)-1H-indol-5-yl)pyrazine-2-carboxamide: a novel, selective, and competitive indole-based lead inhibitor for human monoamine oxidase B WOS:000555606100001 published article about PARKINSONS-DISEASE; DERIVATIVES; SAFINAMIDE; TARGETS; OPTIMIZATION; SEMBRAGILINE; PHARMACOLOGY; MODELS; POTENT in [Elkamhawy, Ahmed; Lee, Kyeong; Pae, Ae Nim; Park, Ki Duk] Dongguk Univ Seoul, Coll Pharm, Goyang 10326, South Korea; [Elkamhawy, Ahmed] Mansoura Univ, Fac Pharm, Dept Pharmaceut Organ Chem, Mansoura, Egypt; [Paik, Sora; Roh, Eun Joo] Korea Inst Sci & Technol KIST, Chem Kin Res Ctr, Seoul 02792, South Korea; [Kim, Hyeon Jeong; Park, Jong-Hyun; Londhe, Ashwini M.] Korea Inst Sci & Technol KIST, Convergence Res Ctr Diag Treatment & Care Syst De, Seoul, South Korea; [Kim, Hyeon Jeong] Yonsei Univ, Dept Biotechnol, Seoul, South Korea; [Londhe, Ashwini M.; Pae, Ae Nim; Park, Ki Duk; Roh, Eun Joo] Korea Univ Sci & Technol, KIST Sch, Div Biomed Sci & Technol, Seoul, South Korea; [Park, Ki Duk] Kyung Hee Univ, KHU KIST Dept Converging Sci & Technol, Seoul, South Korea in 2020, Cited 52. Formula: C5H4N2O2. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5

Herein, two new series ofN-substituted indole-based analogues were rationally designed, synthesizedviamicrowave heating technology, and evaluated as noteworthy MAO-B potential inhibitors. Compared to the reported indazole-based hitsVIandVII, compounds4band4eexhibited higher inhibitory activities over MAO-B with IC(50)values of 1.65 and 0.78 mu M, respectively. When compared to the modest selectivity index of rasagiline (II, a well-known MAO-B inhibitor, SI > 50), both4band4ealso showed better selectivity indices (SI > 60 and 120, respectively). A further kinetic evaluation of the most potent derivative (4e) displayed a competitive mode of inhibition (inhibition constant (K-i)/MAO-B = 94.52 nM). Reasonable explanations of the elicited biological activities were presentedviaSAR study and molecular docking simulation. Accordingly, the remarkable MAO-B inhibitory activity of4e(N-(1-(3-fluorobenzoyl)-1H-indol-5-yl)pyrazine-2-carboxamide), with its selectivity and competitive inhibition, advocates its potential role as a promising lead worthy of further optimization.

Formula: C5H4N2O2. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Elkamhawy, A; Paik, S; Kim, HJ; Park, JH; Londhe, AM; Lee, K; Pae, AN; Park, KD; Roh, EJ or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Recently I am researching about CROSS-COUPLING REACTIONS; CARBOXYLIC-ACIDS; QUINOLINE; SITE; DERIVATIVES; CARBONYLATION; COMPLEXES; RECEPTOR, Saw an article supported by the Education Department of Henan Province [20 A210023]; Henan Agricultural University [30500567, 30500701]; Key Science and the Technology Program of Science and Technology Department of Henan Province [152102210058, 122102210129]. Published in WILEY-V C H VERLAG GMBH in WEINHEIM ,Authors: Hu, JY; Ye, XF; Hao, S; Zhao, QR; Zhao, MQ; Wei, YW; Wu, ZY; Wang, N; Ji, XM. The CAS is 98-97-5. Through research, I have a further understanding and discovery of Pyrazine-2-carboxylic acid. Formula: C5H4N2O2

A highly efficient and simple procedure for the synthesis quinoline-3-carboxamides and their analogues via amidation reaction of quinoline-3-carboxylic acids with tetraalkylthiuram disulfides has been developed. The reaction proceeds efficiently under simple reaction conditions and features the generality of broad scope of substrates with good yields. This protocol provides a convenient procedure for the synthesis of various aza-heteroaromatic carboxamides, which is of pharmaceutical interest.

Formula: C5H4N2O2. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Hu, JY; Ye, XF; Hao, S; Zhao, QR; Zhao, MQ; Wei, YW; Wu, ZY; Wang, N; Ji, XM or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Hassan, NW; Saudi, MN; Abdel-Ghany, YS; Ismail, A; Elzahhar, PA; Sriram, D; Nassra, R; Abdel-Aziz, MM; El-Hawash, SA in [Hassan, Nayera W.; Saudi, Manal N.; Abdel-Ghany, Yasser S.; Ismail, Azza; Elzahhar, Perihan A.; El-Hawash, Soad A.] Alexandria Univ, Fac Pharm, Dept Pharmaceut Chem, Alexandria 21521, Egypt; [Sriram, Dharmarajan] Birla Inst Technol & Sci Pilani, Med Chem & Drug Discovery Res Lab, Pharm Grp, Hyderabad Campus, Jawahar Nagar 500078, Telangana, India; [Nassra, Rasha] Alexandria Univ, Fac Med, Dept Med Biochem, Alexandria, Egypt; [Abdel-Aziz, Marwa M.] Al Azhar Univ, Reg Ctr Mycol & Biotechnol, Cairo 11759, Egypt published Novel pyrazine based anti-tubercular agents: Design, synthesis, biological evaluation and in silico studies in 2020, Cited 84. Recommanded Product: Pyrazine-2-carboxylic acid. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5.

TB continues to be a leading health threat despite the availability of powerful anti-TB drugs. We report herein the design and synthesis of various hybrid molecules comprising pyrazine scaffold and various formerly identified anti-mycobacterial moieties. Thirty-one compounds were screened in vitro for their activity against Mycobacterium tuberculosis H37Rv strain using MABA assay. The results revealed that six compounds (8a, 8b, 8c, 8d, 14b and 18) displayed significant activity against Mtb with MIC values <= 6.25 mu g/ml versus 6.25 mu g/ml for pyrazinamide. The most active compounds were then assessed for their in vitro cytotoxicity against PBMC normal cell line using MTT assay and showed SI > 200. Several in silico studies have been carried out for target fishing of the novel compounds such as shape-based similarity, pharmacophore mapping and inverse docking. Based on this multi-step target fishing study, we suggest that pantothenate synthetase could be the possible target responsible for the action of these compounds. The most active compounds were then successfully docked into the active site of pantothenate synthetase enzyme with favorable binding interactions. In addition, in silico prediction of physicochemical, ADMET and drug-like properties were also determined indicating that compounds 8b, 8c and 8d are promising candidates for the development of new anti-TB agents with enhanced activity and better safety profile.

About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Hassan, NW; Saudi, MN; Abdel-Ghany, YS; Ismail, A; Elzahhar, PA; Sriram, D; Nassra, R; Abdel-Aziz, MM; El-Hawash, SA or concate me.. Recommanded Product: Pyrazine-2-carboxylic acid

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Recommanded Product: 98-97-5. Recently I am researching about ACID-DERIVATIVES; IN-VIVO, Saw an article supported by the Sapienza Funding. Published in ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER in ISSY-LES-MOULINEAUX ,Authors: Pandolfi, F; D’Acierno, F; Bortolami, M; De Vita, D; Gallo, F; De Meo, A; Di Santo, R; Costi, R; Simonetti, G; Scipione, L. The CAS is 98-97-5. Through research, I have a further understanding and discovery of Pyrazine-2-carboxylic acid

Candida albicans biofilm represents a major clinical problem due to its intrinsic tolerance to anti-fungal compounds and it has been highly related to infections in catheterized patients. Few compounds are described as able to inhibit biofilm formation or to interfere with preformed biofilm of C. albicans. Here we report the in vitro evaluation of anti-biofilm activity on C albicans ATCC 10231 of a series of new and already known amine and amide indole derivatives. Among the studied compounds, fifteen resulted active on C albicans ATCC 10231 biofilm, with BMIC50 <= 16 mu g/mL. Three of them (7, 23 and 33) showed a selectivity towards mature biofilm and the most active of them was the compound 23 (BMIC50 = 4 mu g/mL). On the other hands, two different compounds (21 and 22) were selective towards biofilm formation with BMIC50 values of 8 mu g/mL Otherwise, compounds 16 and 17 resulted active on biofilm formation, with BMIC50 of 8 mu g/mL and 2 mu g/mL respectively, and on mature biofilm with BMIC50 of 2 mu g/mL. These two last compounds also showed an interesting activity towards the planktonic cells of C albicans. A selection of the more active compounds was also evaluated on different C albicans strains (PMC1042, PMC1083 and ATCC 10261), showing a comparable or higher anti-biofilm activity, especially on mature biofilm. In vivo toxicity studies using the Galleria mellonella larvae, were finally carried out on more active indole derivatives, showing that they are poorly toxic even at the highest concentrations tested (500-1000 mu g/mL). (C) 2019 Elsevier Masson SAS. All rights reserved. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Pandolfi, F; D'Acierno, F; Bortolami, M; De Vita, D; Gallo, F; De Meo, A; Di Santo, R; Costi, R; Simonetti, G; Scipione, L or concate me.. Recommanded Product: 98-97-5

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

An article A metal-free picolinamide assisted electrochemical ortho-trifluoromethylation of arylamines WOS:000603489100001 published article about C-H BOND; PALLADIUM-CATALYZED TRIFLUOROMETHYLATION; FLUORINATION; ALKENES; FUNCTIONALIZATION; ARYL; ACTIVATION; EFFICIENT; AMINOTRIFLUOROMETHYLATION; PERFLUOROALKYLATION in [Wang, Kai; Zhang, Changjun; Xie, Yuanyuan] Zhejiang Univ Technol, Collaborat Innovat Ctr Yangtze River Delta Reg Gr, Hangzhou 310014, Peoples R China; [Hou, Jiahao; Wei, Tingting; Bai, Renren; Xie, Yuanyuan] Zhejiang Univ Technol, Coll Pharmaceut Sci, Hangzhou 310014, Peoples R China in 2021, Cited 74. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5. Formula: C5H4N2O2

An eco-friendly and effective electrochemical process was developed for the ortho-trifluoromethylation of arylamines using CF3SO2Na as the trifluoromethyl source, affording the desired products in moderate to good yields with high regioselectivity under mild reaction conditions. Importantly, the requirement for both transition metals and oxidants utilized in previous methods were avoided. A radical mechanism was proposed on the basis of various control experiments. (C) 2020 Elsevier Ltd. All rights reserved.

About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Wang, K; Hou, JH; Wei, TT; Zhang, CJ; Bai, RR; Xie, YY or concate me.. Formula: C5H4N2O2

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

I found the field of Biochemistry & Molecular Biology; Chemistry very interesting. Saw the article Synthesis, antimicrobial and chitinase inhibitory activities of 3-amidocoumarins published in 2020. Recommanded Product: Pyrazine-2-carboxylic acid, Reprint Addresses Katiyar, D (corresponding author), Banaras Hindu Univ, Dept Chem, MMV, Varanasi 221005, Uttar Pradesh, India.. The CAS is 98-97-5. Through research, I have a further understanding and discovery of Pyrazine-2-carboxylic acid

A series of 3-amidocoumarins has been synthesized and tested in vitro for their anitimicrobial and chitinase inhibitory activities. Among these, compounds 5k, 5l, 8b-8d, 8f and 8g exhibited good antibacterial activity with MIC values in the range of 6.25-25 mu g/mL against some of the tested strains while compounds 5l, 8b, 8c and 8f showed good activity against at least one or two fungal strains. Some of the assayed compounds 5d, 5k, 5l, 8b and 8c displayed significant chitinase inhibitory activity with IC50, values in the range of 3.74-5.6 mu M. Among them, 5l proved to be potent chitinase inhibitor with IC50 value of 3.74 mu M. To better understand the enzyme-inhibitor interactions molecular docking study of all the synthesized compounds was carried out on Aspergillus fumigatus chitinase 1W9U. The compound 5l showed high binding affinity with the receptor with binding energy value of -8.44 Kcal/mol. This study also provides structure activity relationship (SAR) of synthesized compounds.

Recommanded Product: Pyrazine-2-carboxylic acid. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Sharma, RK; Singh, V; Tiwari, N; Butcher, RJ; Katiyar, D or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

An article Novel pyrazine based anti-tubercular agents: Design, synthesis, biological evaluation and in silico studies WOS:000516796900043 published article about MYCOBACTERIUM-TUBERCULOSIS; ANTIMYCOBACTERIAL ACTIVITY; ACID HYDRAZONES; DERIVATIVES; RESISTANCE; DOCKING; DRUGS; GRANULOCYTES; INHIBITORS; PREDICTION in [Hassan, Nayera W.; Saudi, Manal N.; Abdel-Ghany, Yasser S.; Ismail, Azza; Elzahhar, Perihan A.; El-Hawash, Soad A.] Alexandria Univ, Fac Pharm, Dept Pharmaceut Chem, Alexandria 21521, Egypt; [Sriram, Dharmarajan] Birla Inst Technol & Sci Pilani, Med Chem & Drug Discovery Res Lab, Pharm Grp, Hyderabad Campus, Jawahar Nagar 500078, Telangana, India; [Nassra, Rasha] Alexandria Univ, Fac Med, Dept Med Biochem, Alexandria, Egypt; [Abdel-Aziz, Marwa M.] Al Azhar Univ, Reg Ctr Mycol & Biotechnol, Cairo 11759, Egypt in 2020, Cited 84. Name: Pyrazine-2-carboxylic acid. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5

TB continues to be a leading health threat despite the availability of powerful anti-TB drugs. We report herein the design and synthesis of various hybrid molecules comprising pyrazine scaffold and various formerly identified anti-mycobacterial moieties. Thirty-one compounds were screened in vitro for their activity against Mycobacterium tuberculosis H37Rv strain using MABA assay. The results revealed that six compounds (8a, 8b, 8c, 8d, 14b and 18) displayed significant activity against Mtb with MIC values <= 6.25 mu g/ml versus 6.25 mu g/ml for pyrazinamide. The most active compounds were then assessed for their in vitro cytotoxicity against PBMC normal cell line using MTT assay and showed SI > 200. Several in silico studies have been carried out for target fishing of the novel compounds such as shape-based similarity, pharmacophore mapping and inverse docking. Based on this multi-step target fishing study, we suggest that pantothenate synthetase could be the possible target responsible for the action of these compounds. The most active compounds were then successfully docked into the active site of pantothenate synthetase enzyme with favorable binding interactions. In addition, in silico prediction of physicochemical, ADMET and drug-like properties were also determined indicating that compounds 8b, 8c and 8d are promising candidates for the development of new anti-TB agents with enhanced activity and better safety profile.

Name: Pyrazine-2-carboxylic acid. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Hassan, NW; Saudi, MN; Abdel-Ghany, YS; Ismail, A; Elzahhar, PA; Sriram, D; Nassra, R; Abdel-Aziz, MM; El-Hawash, SA or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Authors Dong, XW; Zhang, JK; Xu, L; Che, JX; Cheng, G; Hu, XB; Sheng, L; Gao, AH; Li, J; Liu, T; Hu, YZ; Zhou, YB in ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER published article about BIOLOGICAL EVALUATION; MOLECULAR DOCKING; 20S PROTEASOME; DESIGN; DERIVATIVES; IDENTIFICATION; DEGRADATION; GENERATION; APOPTOSIS; MYELOMA in [Dong, Xiao-Wu; Zhang, Jian-Kang; Che, Jin-Xin; Liu, Tao; Hu, Yong-Zhou] Zhejiang Univ, ZJU ENS Joint Lab Med Chem, Zhejiang Prov Key Lab Anticanc Drug Res, Hangzhou Inst Innovat Med,Coll Pharmaceut Sci, Hangzhou 310058, Zhejiang, Peoples R China; [Xu, Lei; Hu, Xiao-Bei; Sheng, Li; Gao, An-Hui; Li, Jia; Liu, Tao; Zhou, Yu-Bo] Chinese Acad Sci, Shanghai Inst Mat Med, State Key Lab Drug Res, Natl Ctr Drug Screening, Shanghai 201203, Peoples R China; [Xu, Lei; Hu, Xiao-Bei; Sheng, Li; Gao, An-Hui; Li, Jia; Zhou, Yu-Bo] Univ Chinese Acad Sci, 19A Yuquan Rd, Beijing 100049, Peoples R China; [Zhang, Jian-Kang] Zhejiang Univ City Coll, Sch Med, Hangzhou 310015, Zhejiang, Peoples R China; [Cheng, Gang] Zhejiang Chinese Med Univ, Coll Pharmaceut Sci, Hangzhou 311402, Zhejiang, Peoples R China in 2019, Cited 33. Safety of Pyrazine-2-carboxylic acid. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5

The potential of specific proteasome inhibitors to act as anti-cancer agents has attracted intensive investigations. The proteasome can be covalently inhibited by epoxyketone derivatives via a two-step reaction. Several computational approaches have been developed to mimic the covalent binding event. Compound 1 composed of a six-membered heterocyclic ring was designed by using covalent docking. With a possible different binding mode from the clinical compound Carfilzomib, it occupied the 55 pocket of 20S proteasome and showed favorable inhibitory activity. Subsequently optimization and evaluation were taken place. Among these compounds, 11h demonstrated extraordinary in vitro inhibitory activity and selectivity, and good in vivo proteasome inhibitory activity, a favorable pharmacokinetic profile and xenograft tumor inhibition. The possible binding pattern of compound 11h against proteasome was further fully explored via calculations, providing a theoretical basis for finding potent proteasome inhibitors. (C) 2018 Elsevier Masson SAS. All rights reserved.

Safety of Pyrazine-2-carboxylic acid. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Dong, XW; Zhang, JK; Xu, L; Che, JX; Cheng, G; Hu, XB; Sheng, L; Gao, AH; Li, J; Liu, T; Hu, YZ; Zhou, YB or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Authors Dumpala, RMR; Srivastava, A; Rawat, N in PERGAMON-ELSEVIER SCIENCE LTD published article about MONOCARBOXYLATE-N-OXIDES; PYRIDINE MONOCARBOXYLATES; COMPLEXES; PYRAZINES; THORIUM; NPO2+; PLUTONIUM; CHEMISTRY; EU(III); SPECTRA in [Dumpala, Rama Mohana Rao; Srivastava, Ashutosh; Rawat, Neetika] Bhabha Atom Res Ctr, Radiochem Div, Mumbai 400085, Maharashtra, India in 2021, Cited 53. COA of Formula: C5H4N2O2. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5

Pyrazines are omnipresent in nature and have their occurrence in plants, microbes, food supplies, marine arenas. The present studies aimed at aquatic speciation of the neptunyl ion (NpO2+) with two pyrazine compounds namely pyrazine monocarboxylic acid (PMC) and pyrazine dicarboxylic acid (PDC). Absorption spectrophotometry was used to probe the stability, speciation and spectral properties for the complexation process. NpOO2+ forms a more stable complex with PMC than PDC for 1:1 (ML), while for 1:2 (ML2) the opposite trend is observed. The extent of shift in lambda(max), which is also an indicator for the strength of complexation, reflected similar trends for the complexation process. Isothermal titration calorimetry was employed to determine the enthalpies of complex formation, which is found to be endothermic. The complexation process is entropy driven. Linear free energy correlations were established to retrieve the coordination modes of the complexes. The variation in peak potentials (the cyclic voltammograms) with change in pH and metal to ligand ratio were explored to understand redox speciation, electron transfer kinetics and Eh-pH characteristics for the interaction of NpOO2+ with pyrazine carboxylate ligands. Density functional theory calculations were employed to optimize the geometries and to calculate the bond distances and partial charges on key atoms of the optimized geometries. The theoretical calculations helped to reveal the contributions from two different configurations of the same geometry towards the optical absorption. The bond distances and partial charges estimated theoretically helped to understand the aqueous interactions at the molecular level. (C) 2021 Elsevier Ltd. All rights reserved.

COA of Formula: C5H4N2O2. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Dumpala, RMR; Srivastava, A; Rawat, N or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem

Safety of Pyrazine-2-carboxylic acid. Authors Guin, S; Dolui, P; Zhang, XL; Paul, S; Singh, VK; Pradhan, S; Chandrashekar, HB; Anjana, SS; Paton, RS; Maiti, D in WILEY-V C H VERLAG GMBH published article about in [Guin, Srimanta; Dolui, Pravas; Paul, Satyadip; Singh, Vikas Kumar; Pradhan, Sukumar; Chandrashekar, Hediyala B.; Anjana, S. S.; Maiti, Debabrata] Indian Inst Technol, Dept Chem, Mumbai 400076, Maharashtra, India; [Zhang, Xinglong; Paton, Robert S.] Univ Oxford, Chem Res Lab, Dept Chem, Mansfield Rd, Oxford OX1 3TA, England in 2019, Cited 72. The Name is Pyrazine-2-carboxylic acid. Through research, I have a further understanding and discovery of 98-97-5

Directed C-H functionalization has been realized as a complementary tool to the traditional approaches for a straightforward access of non-proteinogenic amino acids; albeit such a process is restricted mostly up to the gamma-position. In the present work, we demonstrate the diverse (hetero) arylation of amino acids and analogous aliphatic amines selectively at the remote delta-position by tuning the reactivity controlled by ligands. An organopalladium delta-C(sp(3))-H activated intermediate has been isolated and crystallographically characterized. Mechanistic investigations carried out experimentally in conjunction with computational studies shed light on the difference in the mechanistic picture depending on the substrate structure.

Safety of Pyrazine-2-carboxylic acid. About Pyrazine-2-carboxylic acid, If you have any questions, you can contact Guin, S; Dolui, P; Zhang, XL; Paul, S; Singh, VK; Pradhan, S; Chandrashekar, HB; Anjana, SS; Paton, RS; Maiti, D or concate me.

Reference:
Patent; Chevron Research Company; US4732894; (1988); A;,
Pyrazine – Wikipedia,
Pyrazine | C4H4N2 – PubChem