Indole Building Blocks

Application In Synthesis of 3,4-Dimethoxybenzaldehyde. Authors Kukkonen, E; Lahtinen, E; Myllyperkio, P; Haukka, M; Konu, J in ROYAL SOC CHEMISTRY published article about in [Kukkonen, Esa; Lahtinen, Elmeri; Haukka, Matti; Konu, Jari] Univ Jyvaskyla, Dept Chem, POB 35, FI-40014 Jyvaskyla, Finland; [Myllyperkio, Pasi] Univ Jyvaskyla, Nanosci Ctr, POB 35, FI-40014 Jyvaskyla, Finland in 2021, Cited 46. The Name is 3,4-Dimethoxybenzaldehyde. Through research, I have a further understanding and discovery of 120-14-9

Series of highly polar stilbene (1a-e), diphenylbutadiene (2a-c) and phenylethenyIthiophene (3a-c) derivatives were prepared via Horner-Wadsworth-Emmons method with a view to produce new and efficient materials for second harmonic generation (SHG) in the solid-state. The single-crystal X-ray structures of compounds 1-3 reveal extensive polymorphism and a peculiar photodimerization of the 2-chloro-3,4-dimethoxy-4′-nitrostilbene derivative 1a to afford two polymorphs of tetra-aryl cyclobutane 4. The stilbene congeners 2-chloro-3,4-dimethoxy-4′-nitrostilbene (1a. non-centro), 5-bromo-2-hydroxy-3-nitro-4′-nitrostilbene (1b) and 4-dimethylamino-4′-nitrostilbene (1e), as well as 4′-fIuoro-4 ”-nitro-1,4-diphenyl-1,3-butadiene (2a) present the ideal, non-centrosymmetric arrangement of the chromophores for nonlinear optical (NLO) activity. Compounds lb and 2a exhibit only relatively Low intensity for second harmonic generation (0.04 and 0.18 times that of urea reference, respectively), while the stilbene polymorph 1a.non-centro shows NLO activity of over 32 times that of urea. In addition, the conjugated diaromatic compounds 1-3 display fluorescence behaviour in CH2Cl2 solutions with the exception of stilbene derivative 1b.

Application In Synthesis of 3,4-Dimethoxybenzaldehyde. Bye, fridends, I hope you can learn more about C9H10O3, If you have any questions, you can browse other blog as well. See you lster.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

An article Chemical synthesis, microbial transformation and biological evaluation of tetrahydroprotoberberines as dopamine D1/D2 receptor ligands WOS:000465176600016 published article about BERBERINE ANALOGS; L-STEPHOLIDINE; ANTAGONIST; D-1; PHARMACOLOGY; DISCOVERY; ECOPIPAM; (-)-STEPHOLIDINE; IDENTIFICATION; DERIVATIVES in [Ge, Haixia; Qiang, Kun; Chen, Chao; Sun, Laiyu] Huzhou Univ, Sch Life Sci, Huzhou 313000, Peoples R China; [Zhang, Yan; Zhang, Jian] China Pharmaceut Univ, Sch Tradit Chinese Pharm, State Key Lab Nat Med, Nanjing 210009, Jiangsu, Peoples R China; [Yang, Zhuo; Chen, Ming] Chinese Acad Sci, Shanghai Inst Biol Sci, Shanghai Inst Biochem & Cell Biol, Chem Biol Core Facil, Shanghai 200031, Peoples R China in 2019.0, Cited 42.0. Formula: C7H6O2. The Name is 3-Hydroxybenzaldehyde. Through research, I have a further understanding and discovery of 100-83-4

Dopamine D1/D2 receptors are important targets for drug discovery in the treatment of central nervous system diseases. To discover new and potential D1/D2 ligands, 17 derivatives of tetrahydroprotoberberine (THPB) with various substituents were prepared by chemical synthesis or microbial transformation using Streptomyces griseus ATCC 13273. Their functional activities on D1 and D2 receptors were determined by cAMP assay and calcium flux assay. Seven compounds showed high activity on D1/D2 receptor with low IC50 values less than 1 mu M. Especially, top compound 5 showed strong antagonistic activity on both D1 and D2 receptor with an IC50 of 0.391 and 0.0757 mu M, respectively. Five compounds displayed selective antagonistic activity on D1 and D2 receptor. The SAR studies revealed that (1) the hydroxyl group at C-9 position plays an important role in keeping a good activity and small or fewer substituents on ring D of THPBs may also stimulate their effects, (2) the absence of substituents at C-9 position tends to be more selective for D2 receptor, and (3) hydroxyl substitution at C-2 position and the substitution at C-9 position may facilitate the conversion of D1 receptor from antagonist to agonist. Molecular docking simulations found that Asp 103/Asp 114, Ser 107/Cys 118, and Trp 285/Trp 386 of D1/D2 receptors are the key residues, which have strong interactions with the active D1/D2 compounds and may influence their functional profiles.

Bye, fridends, I hope you can learn more about C7H6O2, If you have any questions, you can browse other blog as well. See you lster.. Formula: C7H6O2

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

In 2019 SENSOR ACTUAT B-CHEM published article about CD2+ COORDINATION POLYMERS; HIGHLY SELECTIVE DETECTION; ORGANIC FRAMEWORK; CRYSTAL-STRUCTURE; LUMINESCENT MOF; CUCURBITURIL; EXPLOSIVES; DERIVATIVES; SENSOR; OPPORTUNITIES in [Zhang, Xiu-Du; Zhao, Yue; Chen, Kai; Guo, Jin-Han; Wang, Peng; Wu, Hua; Sun, Wei-Yin] Nanjing Univ, Collaborat Innovat Ctr Adv Microstruct, Nanjing Natl Lab Microstruct,Sch Chem & Chem Engn, Coordinat Chem Inst,State Key Lab Coordinat Chem, Nanjing 210023, Jiangsu, Peoples R China; [Chen, Kai] Nanjing Univ Informat Sci & Technol, Sch Environm Sci & Engn, Jiangsu Key Lab Atmospher Environm Monitoring & P, Collaborat Innovat Ctr Atmospher Environm & Equip, Nanjing 210044, Jiangsu, Peoples R China in 2019, Cited 59. The Name is Benzyl Alcohol. Through research, I have a further understanding and discovery of 100-51-6. Quality Control of Benzyl Alcohol

Efficiently and selectively detecting definite organic compound is attractive but challenging. In this study, we report two novel cucurbit[6]uril (Q[6]) – based supramolecular assemblies {(NH4)(2)[Zn(H2O)(6)][Mg(TPTCA) (H2O)(2)](4)(Q[6])(6)}center dot 66H(2)O (1) and { [Zn(PBPCA)(H2O)(2)]Q[6]center dot 21H(2)O (2) [H(3)TPTCA = [1,1′: 3′,1 ”-terphenyl]-4, 4 ”,5′-tricarboxylic acid and H(2)PBPCA = pyridine-3,5-bis(phenyl-4-carboxylic acid)] by using metal complexes with multiaromatic carboxylate ligands as structure-directing agent. The formation of these assemblies is ascribed to the non-covalent pi-pi, C-H-pi, hydrogen bonding interactions between the outer-surface of Q[6] and coordination complexes. More impressively, 1 and 2 exhibit enhanced fluorescence compared with the ligands and can serve as chemical sensors for aromatic amines and nitroaromatic compounds, particularly for 2,4,6-trinitrophenol (TNP), via fluorescence quenching effect with high selectivity and sensitivity.

Quality Control of Benzyl Alcohol. About Benzyl Alcohol, If you have any questions, you can contact Zhang, XD; Zhao, Y; Chen, K; Guo, JH; Wang, P; Wu, H; Sun, WY or concate me.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

An article Sustainable aromatic polyesters with 1,5-disubstituted indole units WOS:000649534900037 published article about TEREPHTHALATE POLYESTERS; CATALYTIC CONVERSION; THERMAL-PROPERTIES; BUILDING-BLOCKS; BIFURAN DIESTER; VANILLIC ACID; DEGRADATION; CRYSTALLIZATION; COPOLYESTERS; BIOPOLYMER in [Wang, Ping; Zhang, Baozhong] Lund Univ, Ctr Anal & Synth, POB 124, SE-22100 Lund, Sweden in 2021.0, Cited 76.0. Category: indole-building-block. The Name is 3,4-Dimethoxybenzaldehyde. Through research, I have a further understanding and discovery of 120-14-9

This work aims to unravel the impact of disubstitution patterns on the physical properties and processing characteristics of indole-based aromatic polyesters. A series of hydroxyl-carboxylate (AB-type) monomers with 1,5-disubstituted indole and 3-6 methylene units was conveniently synthesized and used in bulk polycondensation to yield the corresponding polyesters with decent molecular weight. These new monomers and polyesters showed enhanced thermal stability compared to the previously reported monomers and polyesters with a 1,3-disubstituted indole structure. According to DSC results, these polyesters showed tunable glass transition temperatures (T-g similar to 57-80 degrees C), depending on the length of the aliphatic methylene units. DSC and WAXD measurements revealed that these polymers did not crystalize from melt, but the ones with 3 or 5 methylene units per repeating unit crystalized from solution. Finally, we demonstrated that the new polyesters with 1,5-disubstituted indole units could be crosslinked using sustainable aromatic aldehyde, which could further enhance their thermal properties.

Category: indole-building-block. Welcome to talk about 120-14-9, If you have any questions, you can contact Wang, P; Zhang, BZ or send Email.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

Formula: C7H6O2. Recently I am researching about MULTICOMPONENT REACTIONS; KNOEVENAGEL CONDENSATION; FUSED HETEROCYCLES; ANTITUMOR-ACTIVITY; DERIVATIVES; BEARING; DESIGN; PYRANO; GREEN; POT, Saw an article supported by the Alexander von Humboldt FoundationAlexander von Humboldt Foundation. Published in ARKAT USA INC in GAINESVILLE ,Authors: Abdella, AM; Abdelmoniem, AM; Butenschon, H; Abdelhamid, IA; Elwahy, AHM. The CAS is 100-83-4. Through research, I have a further understanding and discovery of 3-Hydroxybenzaldehyde

A synthesis of novel bis(1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles), bis(4H-chromene-3-carbonitriles) and bis(dihydropyrano[3,2-c]chromenes), which are linked to aliphatic spacers via amide linkages was achieved via multicomponent reactions (MCR) of the appropriate bis-aldehyde with two equivalents of both of malononitrile and 3-methylpyrazol-5-one, dimedone or 4-hydroxycoumarin in a basic solution. [GRAPHICS] .

Welcome to talk about 100-83-4, If you have any questions, you can contact Abdella, AM; Abdelmoniem, AM; Butenschon, H; Abdelhamid, IA; Elwahy, AHM or send Email.. Formula: C7H6O2

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

Recently I am researching about FUNCTIONAL SELECTIVITY; DRUG DISCOVERY; SEROTONIN; ANTAGONIST; METABOLISM; AGENTS; POTENT; RATS; HIPPOCAMPUS; ANXIOLYTICS, Saw an article supported by the National Science Centre (NCN)National Science Centre, Poland [2015/19/B/NZ7/03543]. Published in AMER CHEMICAL SOC in WASHINGTON ,Authors: Sniecikowska, J; Gluch-Lutwin, M; Bucki, A; Wieckowska, A; Siwek, A; Jastrzebska-Wiesek, M; Partyka, A; Wilczynska, D; Pytka, K; Latacz, G; Przejczowska-Pomierny, K; Wyska, E; Wesolowska, A; Pawlowski, M; Newman-Tancredi, A; Kolaczkowski, M. The CAS is 150-19-6. Through research, I have a further understanding and discovery of m-Methoxyphenol. COA of Formula: C7H8O2

Novel 1-(1-benzoylpiperidin-4-yl)methanamine derivatives with high affinity and selectivity for serotonin 5-HT1A receptors were obtained and tested in four functional assays: ERK1/2 phosphorylation, adenylyl cyclase inhibition, calcium mobilization, and beta-arrestin recruitment. Compounds 44 and 56 (2-methylaminophenoxyethyl and 2-(1H-indol-4-yloxy)ethyl derivatives, respectively) were selected as biased agonists with highly differential signaling fingerprints that translated into distinct in vivo profiles. In vitro, 44 showed biased agonism for ERK1/2 phosphorylation and, in vivo, it preferentially exerted an antidepressant-like effect in the Porsolt forced swimming test in rats. In contrast, compound 56 exhibited a first-in-class profile: it preferentially and potently activated beta-arrestin recruitment in vitro and potently elicited lower lip retraction in vivo, a component of serotonergic syndrome. Both compounds showed promising developability properties. The presented 5-HT1A receptor-biased agonists, preferentially targeting various signaling pathways, have the potential to become drug candidates for distinct central nervous system pathologies and possessing accentuated therapeutic activity and reduced side effects.

COA of Formula: C7H8O2. Welcome to talk about 150-19-6, If you have any questions, you can contact Sniecikowska, J; Gluch-Lutwin, M; Bucki, A; Wieckowska, A; Siwek, A; Jastrzebska-Wiesek, M; Partyka, A; Wilczynska, D; Pytka, K; Latacz, G; Przejczowska-Pomierny, K; Wyska, E; Wesolowska, A; Pawlowski, M; Newman-Tancredi, A; Kolaczkowski, M or send Email.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

Safety of (E)-2-Methylbut-2-enoic acid. Chen, Z; Liu, F; Liu, NN in [Chen, Zhou; Liu, Feng; Liu, Nannan] Auburn Univ, Dept Entomol & Plant Pathol, Auburn, AL 36849 USA published Human Odour Coding in the Yellow Fever Mosquito, Aedes aegypti in 2019, Cited 45. The Name is (E)-2-Methylbut-2-enoic acid. Through research, I have a further understanding and discovery of 80-59-1.

Insects use their olfactory systems to obtain chemical information on mating partners, oviposition sites and food. The yellow fever mosquito Aedes aegypti, an important vector of human infectious diseases, shows strong preference for human blood meals. This study investigated the chemical basis of host detection by characterizing the neuronal responses of antenna! olfactory sensilla of female Ae. aegypti to 103 compounds from human skin emanations. The effect of blood feeding on the responses of olfactory sensilla to these odorants was examined as well. Sensilla SBTII, GP, and three functional subtypes of SST (SST1, SST2, and SST3) responded to most of the compounds tested. Olfactory receptor neurons (ORNs) ‘A’ and ‘B’ in the trichoid sensilla, either activated or inhibited, were involved in the odour coding process. Compounds from different chemical classes elicited responses with different temporal structures and different response patterns across the olfactory sensilla. Except for their increased responses to several odorants, blood-fed mosquitoes generally evoked reduced responses to specific aldehydes, alcohols, aliphatics/aromatics, ketones, and amines through the SST1, SST2, SBTI, SBTII and GP sensilla. The odorants eliciting diminished responses in female mosquitoes after blood feeding may be important in Ae. aegypti host-seeking activity and thus can be candidates for mosquito attractants in the process of this disease vector management.

Bye, fridends, I hope you can learn more about C5H8O2, If you have any questions, you can browse other blog as well. See you lster.. Safety of (E)-2-Methylbut-2-enoic acid

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

In 2019 GREEN CHEM published article about AEROBIC OXIDATIVE HYDROXYLATION; HIGHLY EFFICIENT CONVERSION; ARYL BORONIC ACIDS; IPSO-HYDROXYLATION; VISIBLE-LIGHT; CATALYZED HYDROXYLATION; PHOTOREDOX CATALYSIS; PHENOLS; MILD; GENERATION in [Xu, Yu-Ting; Li, Chen-Yuan; Huang, Xiao-Bo; Gao, Wen-Xia; Zhou, Yun-Bing; Liu, Miao-Chang; Wu, Hua-Yue] Wenzhou Univ, Coll Chem & Mat Engn, Wenzhou 325035, Peoples R China in 2019, Cited 46. The Name is 4′-Hydroxyacetophenone. Through research, I have a further understanding and discovery of 99-93-4. Safety of 4′-Hydroxyacetophenone

Photoinduced hydroxylation of boronic acids with molecular oxygen under photocatalyst-free conditions is reported, providing a green entry to a variety of phenols and aliphatic alcohols in a highly concise fashion. This new protocol features photocatalyst-free conditions, wide substrate scope and excellent functional group compatibility.

Safety of 4′-Hydroxyacetophenone. Welcome to talk about 99-93-4, If you have any questions, you can contact Xu, YT; Li, CY; Huang, XB; Gao, WX; Zhou, YB; Liu, MC; Wu, HY or send Email.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

Formula: C8H8O2. Authors Podunavac, M; Mailyan, AK; Jackson, JJ; Lovy, A; Farias, P; Huerta, H; Molgo, J; Cardenas, C; Zakarian, A in WILEY-V C H VERLAG GMBH published article about in [Podunavac, Masa; Mailyan, Artur K.; Jackson, Jeffrey J.; Cardenas, Cesar; Zakarian, Armen] Univ Calif Santa Barbara, Dept Chem & Biochem, Santa Barbara, CA 93106 USA; [Lovy, Alenka; Farias, Paula; Huerta, Hernan; Cardenas, Cesar] Univ Mayor, Ctr Integrat Biol, Fac Sci, Gerosci Ctr Brain Hlth & Metab, Santiago, Chile; [Molgo, Jordi] Univ Paris Saclay, CEA, Inst Sci Vivant Frederic Joliot,Serv Ingn Mol San, ERL CNRS N 9004,Dept Medicaments & Technol Sante, Batiment 152,Point Courrier 24, F-91191 Gif Sur Yvette, France; [Cardenas, Cesar] Buck Inst Res Aging, Novato, CA 94945 USA in 2021.0, Cited 33.0. The Name is 4-Methoxybenzaldehyde. Through research, I have a further understanding and discovery of 123-11-5

The scalable synthesis of the oxaquinolizidine marine natural product desmethylxestospongin B is based on the early application of Ireland-Claisen rearrangement, macrolactamization, and a late-stage installation of the oxaquinolizidine units by lactam reduction. The synthesis serves as the source of material to investigate calcium signaling and its effect on mitochondrial metabolism in various cell types, including cancer cells.

Formula: C8H8O2. About 4-Methoxybenzaldehyde, If you have any questions, you can contact Podunavac, M; Mailyan, AK; Jackson, JJ; Lovy, A; Farias, P; Huerta, H; Molgo, J; Cardenas, C; Zakarian, A or concate me.

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles

Application In Synthesis of 4′-Hydroxyacetophenone. Eltoukhy, A; Jia, Y; Nahurira, R; Abo-Kadoum, MA; Khokhar, I; Wang, JH; Yan, YC in [Eltoukhy, Adel; Jia, Yang; Nahurira, Ruth; Khokhar, Ibatsam; Wang, Junhuan; Yan, Yanchun] Chinese Acad Agr Sci, Grad Sch, Beijing 100081, Peoples R China; [Eltoukhy, Adel; Abo-Kadoum, M. A.] Al Azhar Univ, Dept Bot & Microbiol, Fac Sci, Assiut 71524, Egypt; [Abo-Kadoum, M. A.] Southwest Univ, Inst Modern Biopharmaceut, Sch Life Sci, Chongqing 400715, Peoples R China published Biodegradation of endocrine disruptor Bisphenol A by Pseudomonas putida strain YC-AE1 isolated from polluted soil, Guangdong, China in 2020.0, Cited 55.0. The Name is 4′-Hydroxyacetophenone. Through research, I have a further understanding and discovery of 99-93-4.

Background Bisphenol A is an important organic chemical as an intermediate, final and inert ingredient in manufacturing of many important products like polycarbonate plastics, epoxy resins, flame retardants, food-drink packaging coating, and other. BPA is an endocrine disruptor compound that mimics the function of estrogen causing damage to reproductive organs. Bacterial degradation has been consider as a cost effective and eco-friendly method for BPA degradation compared with physical and chemical methods. This study aimed to isolate and identify bacterial strain capable to degrade and tolerate high concentrations of this pollutant, studying the factors affecting the degradation process and study the degradation mechanism of this strain. Results YC-AE1 is a Gram negative bacterial strain isolated from soil and identified as Pseudomonas putida by 16S rRNA gene sequence and BIOLOG identification system. This strain found to have a high capacity to degrade the endocrine disruptor Bisphenol A (BPA). Response surface methodology using central composite design was used to statistically optimize the environmental factors during BPA degradation and the results obtained by significant model were 7.2, 30 degrees C and 2.5% for optimum initial pH, temperature and inoculum size, respectively. Prolonged incubation period with low NaCl concentration improve the biodegradation of BPA. Analysis of variance (ANOVA) showed high coefficient of determination, R-2 and Adj-R-2 which were 0.9979 and 0.9935, respectively. Substrate analysis found that, strain YC-AE1 could degrade a wide variety of bisphenol A-related pollutants such as bisphenol B, bisphenol F, bisphenol S, Dibutyl phthalate, Diethylhexyl phthalate and Diethyl phthalate in varying proportion. Pseudomonas putida YC-AE1 showed high ability to degrade a wide range of BPA concentrations (0.5-1000 mg l(- 1)) with completely degradation for 500 mg l(- 1) within 72 h. Metabolic intermediates detected in this study by HPLC-MS were identified as 4,4-dihydroxy-alpha-methylstilbene, p-hydroxybenzaldeyde, p-hydroxyacetophenone, 4-hydroxyphenylacetate, 4-hydroxyphenacyl alcohol, 2,2-bis(4-hydroxyphenyl)-1-propanol, 1,2-bis(4-hydroxyphenyl)-2-propanol and 2,2-bis(4-hydroxyphenyl) propanoate. Conclusions This study reports Pseudomonas putida YC-AE1 as BPA biodegrader with high performance in degradation and tolerance to high BPA concentration. It exhibited strong degradation capacity and prominent adaptability towards a wide range of environmental conditions. Moreover, it degrades BPA in a short time via two different degradation pathways.

Welcome to talk about 99-93-4, If you have any questions, you can contact Eltoukhy, A; Jia, Y; Nahurira, R; Abo-Kadoum, MA; Khokhar, I; Wang, JH; Yan, YC or send Email.. Application In Synthesis of 4′-Hydroxyacetophenone

Reference:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
,Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles