Fraser, Craig’s team published research in Journal of Medicinal Chemistry in 2016 | CAS: 622-26-4

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) have been used as an intermediate in the synthetic preparation of cellular-active allosteric inhibitors of FAKFormula: C7H15NO

Formula: C7H15NOIn 2016 ,《Rapid Discovery and Structure-Activity Relationships of Pyrazolopyrimidines That Potently Suppress Breast Cancer Cell Growth via SRC Kinase Inhibition with Exceptional Selectivity over ABL Kinase》 appeared in Journal of Medicinal Chemistry. The author of the article were Fraser, Craig; Dawson, John C.; Dowling, Reece; Houston, Douglas R.; Weiss, Jason T.; Munro, Alison F.; Muir, Morwenna; Harrington, Lea; Webster, Scott P.; Frame, Margaret C.; Brunton, Valerie G.; Patton, E. Elizabeth; Carragher, Neil O.; Unciti-Broceta, Asier. The article conveys some information:

Novel pyrazolopyrimidines displaying high potency and selectivity toward SRC family kinases have been developed by combining ligand-based design and phenotypic screening in an iterative manner. Compounds were derived from the promiscuous kinase inhibitor PP1 to search for analogs that could potentially target a broad spectrum of kinases involved in cancer. Phenotypic screening against MCF7 mammary adenocarcinoma cells generated target-agnostic structure-activity relationships that biased subsequent designs toward breast cancer treatment rather than to a particular target. This strategy led to the discovery of two potent antiproliferative leads with phenotypically distinct anticancer mode of actions. Kinase profiling and further optimization resulted in eCF506, the first small mol. with subnanomolar IC50 for SRC that requires 3 orders of magnitude greater concentration to inhibit ABL. eCF506 exhibits excellent water solubility, an optimal DMPK profile and oral bioavailability, halts SRC-associated neuromast migration in zebrafish embryos without inducing life-threatening heart defects, and inhibits SRC phosphorylation in tumor xenografts in mice. In the experimental materials used by the author, we found 2-(Piperidin-4-yl)ethanol(cas: 622-26-4Formula: C7H15NO)

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) have been used as an intermediate in the synthetic preparation of cellular-active allosteric inhibitors of FAKFormula: C7H15NO

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Wang, Wentian’s team published research in Journal of Medicinal Chemistry in 2019 | CAS: 622-26-4

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) have been used as an intermediate in the synthetic preparation of cellular-active allosteric inhibitors of FAKCategory: piperidines

Category: piperidinesIn 2019 ,《Design and Synthesis of TASIN Analogues Specifically Targeting Colorectal Cancer Cell Lines with Mutant Adenomatous Polyposis Coli (APC)》 appeared in Journal of Medicinal Chemistry. The author of the article were Wang, Wentian; Zhang, Lu; Morlock, Lorraine; Williams, Noelle S.; Shay, Jerry W.; De Brabander, Jef K.. The article conveys some information:

Despite advances in targeted anticancer therapies, there are still no small-mol.-based therapies available that specifically target colorectal cancer (CRC) development and progression, the second leading cause of cancer deaths. We previously disclosed the discovery of truncating adenomatous polyposis coli (APC)-selective inhibitor 1 (TASIN-1), a small mol. that specifically targets colorectal cancer cells lines with truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor gene through inhibition of cholesterol biosynthesis. Here, we report a medicinal chem. evaluation of a collection of TASIN analogs and activity against colon cancer cell lines and an isogenic cell line pair reporting on the status of APC-dependent selectivity. A number of potent and selective analogs were identified, including compounds with good metabolic stability and pharmacokinetic properties. The compounds reported herein represent a first-in-class genotype-selective series that specifically target apc mutations present in the majority of CRC patients and serve as a translational platform toward a targeted therapy for colon cancer. The results came from multiple reactions, including the reaction of 2-(Piperidin-4-yl)ethanol(cas: 622-26-4Category: piperidines)

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) have been used as an intermediate in the synthetic preparation of cellular-active allosteric inhibitors of FAKCategory: piperidines

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Chen, Nanjun’s team published research in Energy & Environmental Science in 2021 | CAS: 1445-73-4

1-Methyl-4-piperidone(cas: 1445-73-4) is a member of piperidine. Piperidine is a key saturated heterocyclic scaffold found in several of the top-selling small molecule pharmaceuticals and natural alkaloids, with a diverse range of biological activities. Hence, continuous efforts have been made to develop convenient methods to prepare piperidine derivatives.Formula: C6H11NO

Chen, Nanjun; Paek, Sae Yane; Lee, Ju Yeon; Park, Jong Hyeong; Lee, So Young; Lee, Young Moo published their research in Energy & Environmental Science in 2021. The article was titled 《High-performance anion exchange membrane water electrolyzers with a current density of 7.68 A cm-2 and a durability of 1000 hours》.Formula: C6H11NO The article contains the following contents:

Low-cost anion exchange membrane (AEM) water electrolyzers (AEMWEs) are a new technol. for the production of high-purity hydrogen; however, their c.d. and durability are far lower than those of proton exchange membrane water electrolyzers (PEMWEs). Here, we report poly(fluorenyl-co-aryl piperidinium) (PFAP)-based anhydrous cathode AEMWEs that exceed the state-of-the-art PEMWEs with respect to c.d. In addition to a rational electrode design, PFAP-based AEMs with a high water diffusivity and ion conductivity are crucial for high-performance AEMWEs. Using platinum-group-metal (PGM) catalysts, the present AEMWEs achieved a new record c.d. of 7.68 A cm-2 at 2.0 V with a 1 M KOH anode, which surpasses that of state-of-the-art PEMWEs (6 A cm-2 at 2.0 V). PGM-free AEMWEs displayed an excellent c.d. of 1.62 A cm-2 at 2.0 V. Importantly, PGM and PGM-free AEMWEs operated stably under a 0.5 A cm-2 c.d. at 60 °C for more than 1000 h. This work sheds light on current high-performance AEMWEs. In the experiment, the researchers used many compounds, for example, 1-Methyl-4-piperidone(cas: 1445-73-4Formula: C6H11NO)

1-Methyl-4-piperidone(cas: 1445-73-4) is a member of piperidine. Piperidine is a key saturated heterocyclic scaffold found in several of the top-selling small molecule pharmaceuticals and natural alkaloids, with a diverse range of biological activities. Hence, continuous efforts have been made to develop convenient methods to prepare piperidine derivatives.Formula: C6H11NO

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Tanaka, Hiroki’s team published research in Advanced Functional Materials in 2020 | CAS: 622-26-4

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) can be used to synthese ursolic acid derivatives, spiroimidazolidinone NPC1L1 inhibitors, neurokinin-2 receptor antagonists, antagonists for inhibition of platelet aggregation.Category: piperidines

《Self-Degradable Lipid-Like Materials Based on “”Hydrolysis accelerated by the intra-Particle Enrichment of Reactant (HyPER)”” for Messenger RNA Delivery》 was written by Tanaka, Hiroki; Takahashi, Tatsunari; Konishi, Manami; Takata, Nae; Gomi, Masaki; Shirane, Daiki; Miyama, Ryo; Hagiwara, Shinya; Yamasaki, Yuki; Sakurai, Yu; Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu; Shinsho, Eiji; Nishida, Ruka; Fukuzawa, Kaori; Yonemochi, Etsuo; Okuwaki, Koji; Mochizuki, Yuji; Nakai, Yuta; Tange, Kota; Yoshioka, Hiroki; Tamagawa, Shinya; Akita, Hidetaka. Category: piperidines And the article was included in Advanced Functional Materials in 2020. The article conveys some information:

RNA-based therapeutics are a promising approach for curing intractable diseases by manipulating various cellular functions. For eliciting RNA (i.e., mRNA and siRNA) functions successfully, the RNA in the extracellular space must be protected and it must be delivered to the cytoplasm. In this study, the development of a self-degradable lipid-like material that functions to accelerate the collapse of lipid nanoparticles (LNPs) and the release of RNA into cytoplasm is reported. An oleic acid-scaffold lipid-like material that mounts all of these units (ssPalmO-Phe) shows superior transfection efficiency to nondegradable or conventional materials. The insertion of the aromatic ring is unexpectedly revealed to contribute to the enhancement of endosomal escape. Since the intracellular trafficking is a sequential process that includes cellular uptake, endosomal escape, the release of mRNA, and translation, the improvement in each process synergistically enhances the gene expression. In the experimental materials used by the author, we found 2-(Piperidin-4-yl)ethanol(cas: 622-26-4Category: piperidines)

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) can be used to synthese ursolic acid derivatives, spiroimidazolidinone NPC1L1 inhibitors, neurokinin-2 receptor antagonists, antagonists for inhibition of platelet aggregation.Category: piperidines

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Wu, Fangrui’s team published research in Journal of Medicinal Chemistry in 2020 | CAS: 87120-72-7

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. The methylamines occur in small amounts in some plants. Many polyfunctional amines (i.e., those having other functional groups in the molecule) occur as alkaloids in plants—for example, mescaline, 2-(3,4,5-trimethoxyphenyl)ethylamine; the cyclic amines nicotine, atropine, morphine, and cocaine; and the quaternary salt choline, N-(2-hydroxyethyl)trimethylammonium chloride, which is present in nerve synapses and in plant and animal cells.Related Products of 87120-72-7

《Discovery, Structure-Activity Relationship, and Biological Activity of Histone-Competitive Inhibitors of Histone Acetyltransferases P300/CBP》 was written by Wu, Fangrui; Hua, Yuanda; Kaochar, Salma; Nie, Shenyou; Lin, Yi-Lun; Yao, Yuan; Wu, Jingyu; Wu, Xiaowei; Fu, Xiaoyong; Schiff, Rachel; Davis, Christel M.; Robertson, Matthew; Ehli, Erik A.; Coarfa, Cristian; Mitsiades, Nicholas; Song, Yongcheng. Related Products of 87120-72-7 And the article was included in Journal of Medicinal Chemistry in 2020. The article conveys some information:

Histone acetyltransferase (HAT) p300 and its paralog CBP acetylate histone lysine side chains and play critical roles in regulating gene transcription. The HAT domain of p300/CBP is a potential drug target for cancer. Through compound screening and medicinal chem., novel inhibitors of p300/CBP HAT with their IC50 values as low as 620 nM were discovered. The most potent inhibitor is competitive against histone substrates and exhibits a high selectivity for p300/CBP. It inhibited cellular acetylation and had strong activity with EC50 of 1-3μM against proliferation of several tumor cell lines. Gene expression profiling in estrogen receptor (ER)-pos. breast cancer MCF-7 cells showed that inhibitor treatment recapitulated siRNA-mediated p300 knockdown, inhibited ER-mediated gene transcription, and suppressed expression of numerous cancer-related gene signatures. These results demonstrate that the inhibitor is not only a useful probe for biol. studies of p300/CBP HAT but also a pharmacol. lead for further drug development targeting cancer. The experimental process involved the reaction of tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7Related Products of 87120-72-7)

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. The methylamines occur in small amounts in some plants. Many polyfunctional amines (i.e., those having other functional groups in the molecule) occur as alkaloids in plants—for example, mescaline, 2-(3,4,5-trimethoxyphenyl)ethylamine; the cyclic amines nicotine, atropine, morphine, and cocaine; and the quaternary salt choline, N-(2-hydroxyethyl)trimethylammonium chloride, which is present in nerve synapses and in plant and animal cells.Related Products of 87120-72-7

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Lai, Shu-Zhen’s team published research in Journal of Organic Chemistry in 2020 | CAS: 87120-72-7

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. Halogenation, in which one or more hydrogen atoms of an amine is replaced by a halogen atom, occurs with chlorine, bromine, and iodine, as well as with some other reagents, notably hypochlorous acid (HClO). With primary amines the reaction proceeds in two stages, producing N-chloro- and N,N-dichloro-amines, RNHCl and RNCl2, respectively. With tertiary amines, an alkyl group may be displaced by a halogen.Related Products of 87120-72-7

《Photoinduced Deaminative Coupling of Alkylpyridium Salts with Terminal Arylalkynes》 was published in Journal of Organic Chemistry in 2020. These research results belong to Lai, Shu-Zhen; Yang, Yu-Ming; Xu, Hai; Tang, Zhen-Yu; Luo, Zhuangzhu. Related Products of 87120-72-7 The article mentions the following:

A novel and simple Z-alkene synthesis by the photocatalyzed coupling reactions of alkylpyridium salts, which were prepared from primary amines, with terminal aryl alkynes at room temperature is reported here. A wide range of primary amines, which contain different functional groups, were tolerated under these conditions. The mild reaction conditions, broad substrate scope, functional group tolerance, and operational simplicity make this deaminative coupling reaction a valuable method in organic syntheses. In addition to this study using tert-Butyl 4-aminopiperidine-1-carboxylate, there are many other studies that have used tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7Related Products of 87120-72-7) was used in this study.

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. Halogenation, in which one or more hydrogen atoms of an amine is replaced by a halogen atom, occurs with chlorine, bromine, and iodine, as well as with some other reagents, notably hypochlorous acid (HClO). With primary amines the reaction proceeds in two stages, producing N-chloro- and N,N-dichloro-amines, RNHCl and RNCl2, respectively. With tertiary amines, an alkyl group may be displaced by a halogen.Related Products of 87120-72-7

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Olsson, Joel S.’s team published research in Journal of Membrane Science in 2019 | CAS: 1445-73-4

1-Methyl-4-piperidone(cas: 1445-73-4) is a member of piperidine. Piperidine is ubiquitous structural motif widely occurred in diverse synthetically and naturally occurring bioactive molecules. Piperidines are an immensely important class of compounds medicinally: the piperidine ring is the most common heterocyclic subunit among FDA approved drugs.Application of 1445-73-4

In 2019,Journal of Membrane Science included an article by Olsson, Joel S.; Pham, Thanh Huong; Jannasch, Patric. Application of 1445-73-4. The article was titled 《Tuning poly(arylene piperidinium) anion-exchange membranes by copolymerization, partial quaternization and crosslinking》. The information in the text is summarized as follows:

Ion exchange membranes with high ionic contents typically suffer from excessive water uptake and dilution effects which compromise both mech. properties and ion conductivity In the present work we develop and compare partial quaternization, copolymerization and crosslinking as three different synthetic strategies to balance the ion exchange capacity (IEC), water uptake and hydroxide conductivity of poly(arylene piperidinium)s, which belong to a new class of alkali-stable anion-exchange membrane materials. Poly(biphenyl N-methylpiperidine) (PBPip) was first produced in a polyhydroxyalkylation reaction of biphenyl and N-methyl-4-piperidone, and then partly quaternized with controlled stoichiometric shortages of alkyl halide to regulate the IEC. In the second approach, a series of copolymers with controlled IEC were prepared by introducing precise amounts of ketone co-monomers in the polyhydroxyalkylations. In the final approach, crosslinked AEMs were fabricated in a reactive casting procedure, followed by partial quaternization. The overall results of the study reveals that the copolymerization approach gives AEMs with the most attractive set of properties. Hence, at a given IEC and moderate water uptake, the copolymer AEMs reach the highest hydroxide conductivity, up to 120 mS cm-1 at 80 °C, and retain the high alk. stability of the original poly(arylene piperidinium) AEM. The study demonstrates the versatility and efficiency of these synthetic strategies to tailor and significantly improve the properties of functional high-performance AEMs for different electrochem. applications. In the part of experimental materials, we found many familiar compounds, such as 1-Methyl-4-piperidone(cas: 1445-73-4Application of 1445-73-4)

1-Methyl-4-piperidone(cas: 1445-73-4) is a member of piperidine. Piperidine is ubiquitous structural motif widely occurred in diverse synthetically and naturally occurring bioactive molecules. Piperidines are an immensely important class of compounds medicinally: the piperidine ring is the most common heterocyclic subunit among FDA approved drugs.Application of 1445-73-4

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Hu, Jiefeng’s team published research in Advanced Synthesis & Catalysis in 2019 | CAS: 87120-72-7

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. Left-handed and right-handed forms (mirror-image configurations, known as optical isomers or enantiomers) are possible when all the substituents on the central nitrogen atom are different (i.e., the nitrogen is chiral). With amines, there is extremely rapid inversion in which the two configurations are interconverted.Product Details of 87120-72-7

In 2019,Advanced Synthesis & Catalysis included an article by Hu, Jiefeng; Cheng, Bo; Yang, Xianyu; Loh, Teck-Peng. Product Details of 87120-72-7. The article was titled 《Transition-Metal-Free Deaminative Vinylation of Alkylamines》. The information in the text is summarized as follows:

An efficient metal-free system, that was capable of activating the C-N bonds of Katritzky pyridinium salts I [R = 3,3-difluorocyclobutyl, cyclohexyl, PhCH2CH(CO2Me), etc.] derived from diverse alkylamines for deaminative vinylation to produce various olefins RCH=CHAr [Ar = Ph, 2-thienyl, 4-FC6H4, etc.]. The key to the high reactivity was the utilization of pyridinium salt-activated alkylamines I with a base as a promoter. The transformation exhibited good functional group compatibility and included inexpensive primary amine feedstocks and amino acids. The proposed method could serve as a powerful synthetic method for late-stage modification of complex compounds Mechanistic experiments suggestes that free radical processes are involved in this system. In the experiment, the researchers used tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7Product Details of 87120-72-7)

tert-Butyl 4-aminopiperidine-1-carboxylate(cas: 87120-72-7) belongs to anime. Left-handed and right-handed forms (mirror-image configurations, known as optical isomers or enantiomers) are possible when all the substituents on the central nitrogen atom are different (i.e., the nitrogen is chiral). With amines, there is extremely rapid inversion in which the two configurations are interconverted.Product Details of 87120-72-7

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Wang, Ke-Rang’s team published research in Chemical Biology & Drug Design in 2016 | CAS: 622-26-4

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) can be used to synthese ursolic acid derivatives, spiroimidazolidinone NPC1L1 inhibitors, neurokinin-2 receptor antagonists, antagonists for inhibition of platelet aggregation.Quality Control of 2-(Piperidin-4-yl)ethanol

In 2016,Wang, Ke-Rang; Qian, Feng; Sun, Qian; Ma, Cui-Lan; Rong, Rui-Xue; Cao, Zhi-Ran; Wang, Xiao-Man; Li, Xiao-Liu published 《Substituent Effects on Cytotoxic Activity, Spectroscopic Property, and DNA Binding Property of Naphthalimide Derivatives》.Chemical Biology & Drug Design published the findings.Quality Control of 2-(Piperidin-4-yl)ethanol The information in the text is summarized as follows:

A series of novel naphthalimide derivatives NI1-5 containing piperazine moieties (N-(2-hydroxyethyl)piperazine and 1-piperazinepropanol) and piperidine moieties (4-piperidinemethanol, 4-hydroxypiperidine and 4-piperidineethanol) have been synthesized and evaluated for their cytotoxic activity, spectroscopic property, and DNA binding behaviors. It was found that substituents at the 4-position remarkably influence the various activities of this series of compound Compounds NI3-5 modified with piperidines exhibited potent cytotoxic activities against Hela, SGC-7901, and A549 cells with the IC50 values from 0.73 μM to 6.80 μM, which are better than NI1-2 functionalized with piperazines. Compounds NI1-2 showed higher binding capacity with Ct-DNA than compounds NI3-5 based on studies of UV-vis, fluorescence and CD spectra. Furthermore, compounds NI3-5, as DNA intercalators, showed fluorescence enhancement upon binding with Ct-DNA. More interestingly, fluorescence imaging studies of compound NI4 with A549 cells showed that the fluorescence predominantly appeared in the cytoplasm. These results provided a potential application of NI3-5 as anticancer therapeutic and cancer cell imaging agents. In the experiment, the researchers used 2-(Piperidin-4-yl)ethanol(cas: 622-26-4Quality Control of 2-(Piperidin-4-yl)ethanol)

2-(Piperidin-4-yl)ethanol(cas: 622-26-4) can be used to synthese ursolic acid derivatives, spiroimidazolidinone NPC1L1 inhibitors, neurokinin-2 receptor antagonists, antagonists for inhibition of platelet aggregation.Quality Control of 2-(Piperidin-4-yl)ethanol

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem

 

Li, Ning’s team published research in Environmental Science & Technology in 2021 | CAS: 826-36-8

Triacetonamine(cas: 826-36-8) is a member of piperidine. Piperidine is a key saturated heterocyclic scaffold found in several of the top-selling small molecule pharmaceuticals and natural alkaloids, with a diverse range of biological activities. Hence, continuous efforts have been made to develop convenient methods to prepare piperidine derivatives.Safety of Triacetonamine

Li, Ning; Li, Rui; Duan, Xiaoguang; Yan, Beibei; Liu, Wen; Cheng, Zhanjun; Chen, Guanyi; Hou, Li’an; Wang, Shaobin published their research in Environmental Science & Technology on December 7 ,2021. The article was titled 《Correlation of active sites to generated reactive species and degradation routes of organics in peroxymonosulfate activation by Co-loaded carbon》.Safety of Triacetonamine The article contains the following contents:

Peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) as an efficient strategy for organic degradation are highly dependent on catalyst design and structured active sites. However, the identification of the active sites and their relationship with reaction mechanisms for organic degradation are not fully understood for a composite catalyst due to the complex structure. Herein, we developed a family of Co encapsulated in N-doped carbons (Co-PCN) with tailored types and contents of active sites via manipulated pyrolysis for PMS activation and ciprofloxacin (CIP) degradation, focusing on the correlation of active sites to generated reactive species and degradation routes of organics The structure-function relationships between the different active sites in Co-PCN catalysts and reactive oxygen species (ROS), as well as bond breaking position of CIP, were revealed through regression anal. and d. functional theory calculation Co-Nx, O-C=O, C=O, graphitic N, and defects in Co-PCN stimulate the generation of 1O2 for oxidizing the C-C bond in the piperazine ring of CIP into C=O. The substitution of F by OH and hydroxylation of the piperazine ring might be induced by SO4•- and •OH, whose formation was affected by C-O, Co(0), Co-Nx, graphitic N, and defects. The findings provided new insights into reaction mechanisms in PMS-AOP systems and rational design of catalysts for ROS-oriented degradation of pollutants. In the experimental materials used by the author, we found Triacetonamine(cas: 826-36-8Safety of Triacetonamine)

Triacetonamine(cas: 826-36-8) is a member of piperidine. Piperidine is a key saturated heterocyclic scaffold found in several of the top-selling small molecule pharmaceuticals and natural alkaloids, with a diverse range of biological activities. Hence, continuous efforts have been made to develop convenient methods to prepare piperidine derivatives.Safety of Triacetonamine

Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem