Coumarin-based octopamine phototriggers and their effects on an insect octopamine receptor

We have developed and characterized efficient caged compounds of the neurotransmitter octopamine. For derivatization, we introduced [6-bromo-8-(diethylaminomethyl)-7-hydroxycoumarin-4-yl]methoxycarbonyl (DBHCMOC) and {6-bromo-7-hydroxy-8-[(piperazin-1-yl)methyl]coumarin-4-yl}methoxycarbonyl (PBHCMOC) moieties as novel photo-removable protecting groups. The caged compounds were functionally inactive when applied to heterologously expressed octopamine receptors (AmOctα1R). Upon irradiation with UV-visible or IR light, bioactive octopamine was released and evoked Ca2+ signals in AmOctα1R-expressing cells. The pronounced water solubility of compounds 2-4 in particular holds great promise for these substances as excellent phototriggers of this important neurotransmitter.     

DMACM-caged adenosine nucleotides: ultrafast phototriggers for ATP,ADP, and AMP activated by long-wavelength irradiation

The development of new photocleavable adenosine nucleotides based on the photochemistry of [7-(dimethylamino)coumarin-4-yl]methyl (DMACM) esters is described. The phototriggers liberate adenosine triphosphate (ATP), diphosphate, and monophosphate upon UV/Vis irradiation between 334 and 405 nm. The efficiency of photocleavage at long wavelengths is high as a result of a combination of appropriate quantum yields and intensive absorptivities. By using time-resolved fluorescence spectroscopy, we determined a lower limit of 1.6 x 10(9) s(-1) for the rate constant of the release of ATP from DMACM-caged ATP. The favorable properties of DMACM-caged ATP were confirmed in physiological studies by confocal laser scanning microscopy. We were able to uncage DMACM-caged ATP in cultures of mouse astrocytes and in brain tissue slices from mice and were also able to measure the effect of photoreleased ATP on the cellular response of astrocytes, namely the ability of the ATP to evoke Ca(2+) ion waves.     

Caged capsaicins: New tools for the examination of TRPV1 channels in somatosensory neurons

The vanilloid capsaicin, N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide, is the pungent ingredient of chili peppers and is used in pain research as an activating ligand of heat-sensitive transduction channels in nociceptive neurons. Here we describe the synthesis and application of two capsaicin derivatives modified at the hydroxy function of the vanillyl motif: alpha-carboxy-4,5-dimethoxy-2-nitrobenzyl-caged (CDMNB-caged) capsaicin and {7-[bis(carboxymethyl)amino]coumarin-4-yl}methoxycarbonyl-caged (BCMACMOC-caged) capsaicin. These compounds show dramatically reduced pungency, but release active capsaicin upon irradiation with UV light. CDMNB-caged capsaicin can be used to perform concentration-jump experiments, while BCMACMOC-caged capsaicin is membrane-impermeant and can be applied selectively to the intracellular or extracellular sides of a plasma membrane. Both compounds can serve as valuable research tools in pain physiology.     

Synthesis of novel tri- and tetrasubstituted C<Subscript>18</Subscript> furan fatty esters

A methylene-interrupted C₁₈ keto-acetylenic fatty ester (methyl 12-oxo-9-octadecynoate) was obtained from methyl ricinoleate by bromination-dehydrobromination followed by oxidation. Reaction of methyl 12-oxo-9-octadecynoate with bis(benzonitrile) palladium(II) chloride, allyl bromide, or methyl-allyl bromide furnished methyl 8-[5-hexyl-3-allyl-furan-2-yl]-octanoate (1, 56%) or methyl 8-[5-hexyl-3-(2-methyl-allyl)-furan-2-yl]-octanoate (2, 55%). Reaction of methyl 12-oxo-11-chloro-or 11-fluoro-9-octadeyynoate (prepared from methyl santalbate-methyl 11-E-9-octadecynoate, found in sandalwood, Santalum album, seed oil) with bis(benzonitrile) palladium(II) chloride gave methyl 8-(4-fluoro-5-hexyl-furan-2-yl)-octanoate (3, 50%) or methyl 8-(4-fluoro-5-hexyl-furan-2-yl)-octanoate (4, 50%), respectively. And when methyl 12-oxo-11-chloro- or 11-fluoro-9-octadecynoate was treated with a mixture of bis(benzonitrile) palladium(II) chloride, allyl bromide, or methyl-allyl bromide, the reaction yielded tetrasubstituted C₁₈ furan derivatives, viz, methyl 8-(3-allyl-4-chloro-5-hexyl-furan-2-yl)-octanoate (5, 54%), methyl 8-[4-chloro-5-hexyl-3-(2-methyl-allyl)-furan-2-yl)-octanoate (6, 54%), methyl 8-(3-allyl-4-fluoro-5-hexyl-furan-2-yl]-octanoate (7, 10%), and methyl 8-[4-fluoro-5-hexyl-3-(2-methyl-allyl)-furan-2-yl]-octanoate (8, 10%). The presence of a fluorine atom in the furan derivatives 4, 7, and 8 was readily characterized by the appearance of doublets for carbon nuclei, which were coupled to the fluorine atom in the ¹³C NMR spectra. All furan fatty derivatives from this work were characterized by NMR spectroscopic and mass spectrometric analyses. The yields of compounds 7 and 8 were very low (10%) despite attempts to improve the procedure by increasing the amounts of the reactants and catalyst.     

头孢三嗪反式异构体合成研究

以头孢主环(6R,7R)-7-氨基-8-氧代-3-[[(1,2,5,6-四氢-2-甲基-5,6-二氧代-1,2,4-三嗪-3-基)硫代]甲基]-5-硫代-1-氮杂双环[4.2.0]辛-2-烯-2-羧酸(7-ACT)为起始原料,与反式活性酯侧链(E)-2-(2-氨基-4-噻唑基)-2-甲氧亚胺-乙酸-2-苯并噻唑硫酯(E-AE)反应作用生成(6R,7R)-7-[2-(2-氨基-4-噻唑基)-(E)-2-(甲氧亚胺)乙酰氨基]-8-氧代-3-[(1,2,5,6-四氢-2-甲基-5,6-二氧代-1,2,4-三嗪-3-基)硫代〗甲基]-5-硫代-1-氮杂双环[4.2.0]辛-2-烯-2-羧酸,然后在丙酮溶液中与异辛酸钠成盐而制得反式头孢三嗪钠。该产品具有良好的稳定性与高纯度,可作为对照品使用。     

含受阻胺结构的苯并三唑光稳定剂的合成及表征

以3-(3′-叔丁基-4′-羟基-苯基)丙酸和邻硝基苯胺或邻硝基对氯苯胺为起始原料经重氮化-偶合、还原、酯化,再与甲基哌啶醇酯交换反应合成了4个分子中含受阻胺结构的苯并三唑化合物,2,2,6,6-四甲基哌啶醇-[3′-(2H-苯并三唑)-5′-叔丁基-4′-羟基-苯基]丙酸酯收率为48.3%;1,2,2,6,6-五甲基哌啶醇-[3′-(2H-苯并三唑)-5′-叔丁基-4′-羟基-苯基]丙酸酯收率为47.0%;2,2,6,6-四甲基哌啶醇-[3′-(5-氯-2H-苯并三唑)-5′-叔丁基-4′-羟基-苯基]丙酸酯的收率为45.7%;1,2,2,6,6-五甲基哌啶醇-[3′-(5-氯-2H-苯并三唑)-5′-叔丁基-4′-羟基-苯基]丙酸酯的收率为44.4%;通过1HNMR、MS和IR确定了化合物分子结构。测定了它们紫外吸收光谱,该4个化合物在270～400nm均有较强的吸收峰。所合成的化合物分子中同时含有紫外吸收和捕获自由基两种功能,是一类双功能光稳定剂。     

香豆素噻唑烷二酮类化合物的合成

运用拼合原理并根据构效关系研究结果,设计了香豆素噻唑烷二酮类化合物,合成方法是以甲基取代的香豆素为原料,经NBS溴化后,再与5-(4-羟基苄叉)-噻唑烷-2,4-二酮在NaH作用下缩合得到,其中中间体5-(4-羟基苄叉)-噻唑烷-2,4-二酮是由噻唑烷二酮与对羟基苯甲醛在哌啶催化下缩合得到,共合成了5-[4-(香豆素-7-亚甲氧基)苄叉]-噻唑烷-2,4-二酮、5-[4-(4-甲基香豆素-7-亚甲氧基)苄叉]-噻唑烷-2,4-二酮、5-[4-(香豆素-6-亚甲氧基)苄叉]-噻唑烷-2,4-二酮、5-[4-(7-甲氧基香豆素-4-亚甲氧基)苄叉]-噻唑烷-2,4-二酮、5-[4-(3-溴香豆素-7-亚甲氧基)苄叉]-噻唑烷-2,4-二酮、5-[4-(3-溴-4-甲基香豆素-7-亚甲氧基)苄叉]-噻唑烷-2,4-二酮6个香豆素噻唑烷二酮类化合物,结构均经IR1、HNMR、MS确定,两步反应合成目标化合物总产率分别为10.4%、13.1%、7.1%、16.0%、22.0%、18.0%。     

Synthesis of pyrazolo[4′,3′:5,6]pyrazino[2,3-c]pyrazoles and pyrazolo[4′,3′:5,6]pyrazino[2,3-d]pyrimidines and their application to polyester fibres

4-Nitroso-1-phenyl-3-methyl-5-aminopyrazole ( 1 ) was condensed with ethylcyanoacetate ( 2 ), malononitrile ( 4a ) and 2-cyanomethylbenzimidazole ( 4b ) to yield 6-hydroxy-5-cyano, 6-amino-5-cyano and 6-amino-5-(benzimidazol-2-yl)-3-methylpyrazolo [3,4-b]pyrazines 3, 5a and 5b , respectively. 5-Cyano-6-chloro derivative 6 obtained from 3 was converted to 3-aminopyrazolo[4′,3′:5,6]pyrazino[2,3-c]pyrazoles 8a and 8b by the treatment with hydrazin hydrate ( 7a ) and phenylhydrazine ( 7b ), respectively. Compound 5a was treated with formamide ( 9a ), urea ( 9b ) and thiourea ( 9c ) to give 4-aminopyrazolo[4′,3′:5,6]pyrazino[2′3′-d]pyrimidines 10a–10c. With refluxing acetic anhydride compounds 8a, 8b and 10a gave corresponding acetamido derivatives 8c, 8d and 10d. Compound 5a was treated with ethylorthoformate ( 11 ), acetic anhydride ( 12 ) or benzoylchloride ( 13 ) to give fused benzimidazopyrazolo[4′,3′:5,6]pyrazino[2′,3′-d]pyrimidines, viz., benzimidazol[1,2-c]pyrazolo[4,3-g]pteridines ( 14a–14c ). Some of the compounds 8, 10 and 14 were applied to polyester as disperse dyes and their fastness properties were studied.     

Investigation of NPB Analogs That Target Phosphorylation of BAD-Ser99 in Human Mammary Carcinoma Cells

The design and development of a small molecule named NPB [3-{(4(2,3-dichlorophenyl)piperazin-1-yl}{2-hydroxyphenyl)methyl}-N-cyclopentylbenzamide], which specifically inhibited the phosphorylation of BAD at Ser99 in human carcinoma cells has been previously reported. Herein, the synthesis, characterization, and effect on cancer cell viability of NPB analogs, and the single-crystal X-ray crystallographic studies of an example compound (4r), which was grown via slow-solvent evaporation technique is reported. Screening for loss of viability in mammary carcinoma cells revealed that compounds such as 2[(4(2,3-dichlorophenyl)piperazin-1-yl][naphthalen-1-yl]methyl)phenol (4e), 5[(4(2,3-dichlorophenyl)piperazin-1-yl][2-hydroxyphenyl)methyl)uran-2-carbaldehyde (4f), 3[(2-hydroxyphenyl][4(p-tolyl)piperazin-1-yl)methyl)benzaldehyde (4i), and NPB inhibited the viability of MCF-7 cells with IC₅₀ values of 5.90, 3.11, 7.68, and 6.5 µM, respectively. The loss of cell viability was enhanced by the NPB analogs synthesized by adding newer rings such as naphthalene and furan-2-carbaldehyde in place of N-cyclopentyl-benzamide of NPB. Furthermore, these compounds decreased Ser99 phosphorylation of hBAD. Additional in silico density functional theory calculations suggested possibilities for other analogs of NPB that may be more suitable for further development.     

Novel functionalized monomers based on kojic acid: snythesis,characterization, polymerization and evalution of antimicrobial activity

Two novel acrylate monomers, [5-(benzyloxy)-4-oxo-4H-pyran-2-yl]methyl acrylate and {1-[(5-(benzyloxy)-4-oxo-4H-pyran-2-yl)methyl]-1,2,3-triazol-4-yl}methyl acrylate were synthesized by the reaction of 5-benzyloxy-2-(hydroxymethyl)-4H-pyran-4-one and 5-(benzyloxy)-2-{[4-(hydroxymethyl)-1,2,3-triazol-1-yl]methyl}-4H-pyran-4-one with acryloyl chloride in the presence of triethylamine, respectively. These monomers were polymerized using 2,2^′-azobisisobutyronitrile (AIBN) as the initiator in N,N-dimethylformamide:14-dioxane (10:1) solution. The thermal behavior of the polymers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized compounds were evaluated for their antibacterial and antifungal activites aganist bacteria and fungi using the disk diffusion method. The results indicated that some of these compounds demonstrated moderate to good antibacterial and antifungal activities.     

The synthesis of fused and pendant pyrazole heterocyclic compounds from 5-amino-3-methyl-1-phenylpyrazole and their evaluation as fluorescent brightening agents

5-Amino-3-methyl-1-phenylpyrazole ( 1 ) has been condensed with EMME ( 2 a) and EMCA ( 2 b) and the resulting ethyl 5-aminoacrylates ( 3 a–b) cyclized to pyrazolo[3,4,-b]pyridines ( 4 a–b). 3-Methyl-1-phenylpyrazol-5-yl diazonium salt ( 7 ), prepared from ( 1 ) was coupled with tobias acid ( 8 ) and 2-methoxy-6-aminoquinoxaline ( 9 ) to get the corresponding O-aminoarylazo and heterylazo dyes ( 10 ) which were oxidatively cyclized to 2-N-(3-methyl-1-N-phenylpyrazol-5-yl)-1,2,3-triazolo[4,5-a] naphthalene and [4,5-f] quinoxaline derivative ( 11 ). The spectral properties of the compounds ( 4 a–b, 5 , 6 , 11 a–b) were studied.     

可分解型磺酸盐阴离子表面活性剂的合成研究

0 .3mol脂肪醛与 0 .4mol原甲酸三乙酯在 1g硝酸铵催化下于 8～ 10℃反应 8h得到脂肪醛缩二乙醇 (Ⅰ) (收率 >5 0 % ) ;Ⅰ在磺基水杨酸的催化下于 110℃与丙三醇反应〔n(丙三醇 )∶n(Ⅰ) =3∶1〕并蒸馏除去生成的乙醇 ,得到 2 烷基 4 羟甲基 1,3 二氧杂环戊烷 (Ⅱ) (收率 >80 % ) ;最后等物质的量的Ⅱ、1,3 丙基磺酸内酯和氢氧化钠于 60～ 65℃反应 8h ,得到系列可分解磺酸盐阴离子表面活性剂 [3 (2 烷基 1,3 二氧杂环戊烷基 4 甲氧基 )丙磺酸钠 ](Ⅲ) ,收率 >90 %。     

Synthesis and Characterization of Cell‐Permeable Caged Phosphates that Can Be Photolyzed by Visible Light or 800 nm Two‐Photon Photolysis

We report the synthesis and photolytic properties of caged inorganic phosphates (Pi compounds) based on the 2‐(4′‐{bis[2‐(2‐methoxyethoxy)ethyl]amino}‐4‐nitro‐[1,1′‐biphenyl]‐3‐yl)propan‐1‐ol (EANBP) and 7‐(diethylamino)coumarin‐4‐yl]methyl (DEACM) protecting groups. The EANBP‐Pi showed unprecedented photolysis efficiency at 405 nm, with 95 % release of free phosphate and a quantum yield of 0.28. Thanks to the high two‐photon sensitivity of the EANBP chromophore, Pi release through two‐photon photolysis is also possible, with an action cross section of 20.5 GM at 800 nm. Two bioactivatable acetoxymethyl protection groups were added to the “caged‐Pi” compounds. The resulting triesters of phosphoric acid were able to diffuse through the cellular membranes of plant cells. Once inside a cell, the cleavage of these biocleavable motifs by intracellular esterases allows intracellular accumulation of EANBP‐Pi. Bis(AM)‐EANBP‐Pi therefore represents a very attractive tool for study of the Pi signal transduction cascade in living cells.     

RNA cleavage without hydrolysis. Splitting the catalytic activities of binase with Asn101 and Thr101 mutations

Members of the microbial guanyl-specific ribonuclease family catalyse the endonucleolytic cleavage of single-stranded RNA in a two-step reaction involving transesterification to form a 2',3'-cyclic phosphate and its subsequent hydrolysis to yield the respective 3'-phosphate. The extracellular ribonuclease from Bacillus intermedius (binase, RNase Bi) shares a common mechanism for RNA hydrolysis with mammalian RNases. Two catalytic residues in the active site of binase, Glu72 and His101, are thought to be involved in general acid-general base catalysis of RNA cleavage. Using site-directed mutagenesis, binase mutants were produced containing amino acid substitutions H101N and H101T and their catalytic properties towards RNA, poly(I), poly(A), GpC and guanosine 2',3'- cyclic phosphate (cGMP) substrates were studied. The engineered mutant proteins are active in the transesterification step which produces the 2',3'-cyclic phosphate species but they have lost the ability to catalyse hydrolysis of the cyclic phosphate to give the 3' monophosphate product.      

Nucleophilic addition of hydrogen sulfide to methyl oleate,methyl linoleate,and soybean oil

Hydrogen sulfide was added to methyl oleate, methyl linoleate, and soybean oil at −70 and 25 C in the presence of boron trifluoride. Major reaction compounds were identified by gas liquid chromatography and mass spectrometry. At −70 C with a 200 molar ratio of hydrogen sulfide to ester, the reactions were complete in 4 hr. Primary reaction product from methyl oleate was methyl 9(10)-mercaptostearate. Methyl linoleate gave ca. equal amounts of methyl 9-(2-pentyl-1-thiolan-5-yl) nonanoate and methyl 8-(2-hexyl-1-thiolan-5-yl) octanoate. At 25 C, the reaction of methyl oleate and linoleate with hydrogen sulfide was less complete, and more side reactions were noted. When equimolar amounts of methyl oleate and methyl 9(10)-mercaptostearate were reacted in the presence of boron trifluoride at 25 C, a new compound was formed, bis(methyl n-octadecanoate 9[10]-yl) sulfide. The addition of liquid hydrogen sulfide to soybean oil at −70 C in the presence of boron trifluoride yields a product which, upon saponification, acidification, and methylation analyzes by gas liquid chromatography as ca. 52% thiolan, 27% mercaptostearate, 10% palmitate, 6% stearate, and 5% unidentified compounds.     

An exploration of corrosion inhibition of mild steel in sulphuric acid solution through experimental study and Monte Carlo simulations

Abstract

4-[4-(1H-imidazol-1-yl)methyl)-1H-1,2,3-triazol-1-yl]methylbenzophenone (ITBP) and 4[4-(1H-1,2,4-triazol-1-yl)methyl)-1H-1,2,3-triazol-1-yl]methylbenzophenone (TTBP) are synthesized as new heterocyclic compounds of the triazole derivative family and tested successfully as potential inhibitors for MS in 1?M H₂SO₄ corrosive medium by using gravimetric analysis, electrochemical impedance spectroscopy, potentiodynamic polarization, and energy dispersive X-ray spectroscopy (EDX). Polarization curves show that the tested inhibitors are mixed-type inhibitors. Scanning electron microscopy (SEM) affirmed the existence of an adsorbed film on the steel surface. Monte Carlo simulations were in excellent agreement with the experimental tests.

Abbreviation: PDP: Potentiodynamic Polarization; EIS: Electrochemical impedance spectroscopy; DFT: Density functional theory; MC: Monte Carlo     

Quinoxaline derivatives as long wavelength photosensitizers in photoinitiated cationic polymerization of diaryliodonium salts

The present paper is focused on visible light initiated cationic polymerizations. Photoinitiated polymerization of representative vinyl ether and oxirane monomers using two quinoxaline derivatives; namely (2-(2,3-dihydrobenzo [b][1,4]dioxin-6-yl)-3-(2,3-dihydrobenzo[b]-[1,4]dioxin-7-yl)-5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-8-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7yl) quinoxaline) (DBQEd) and 2,3,5,8-tetra(thiophen-2-yl)quinoxaline (TTQ) are studied. Novel dyes based on the quinoxaline skeleton are employed as efficient photosensitizers in cationic photopolymerizations. Polymerizations were initiated at room temperature upon irradiation with long-wavelength UV and visible lights in the presence of diphenyliodonium hexafluorophosphate (Ph₂I⁺PF₆^?). The progress of the polymerizations was monitored by optical pyrometry (OP). Solar irradiation is also employed to carry out the cationic polymerization of a diepoxide monomer in the presence of air.     

Discovery of an Orally Active and Long-Acting DPP-IV Inhibitor through Property-Based Optimization with an in Silico Biotransformation Prediction Tool

Long-acting dipeptidyl peptidase IV inhibitors have emerged as promising molecules for interventions for type 2 diabetes. Once weekly dosing brings greater patient compliance and more stable glycemic control. Starting from our previous highly potent compound with a thienoprimidine scaffold, which is unfortunately severely hit by hepatic biotransformation, a lead compound was rapidly generated by drawing on the experience of our previously discovered long-acting compounds with pyrrolopyrimidine scaffold. With the aid of an in silico biotransformation prediction tool, (R)-2-((2-(3-aminopiperidin-1-yl)-4-oxo-6-(pyridin-3-yl)thieno[3,2-d]pyrimidin-3(4H)-yl)methyl)-4-fluorobenzonitrile was eventually generated and determined to have high potency, a fine pharmacokinetic profile, and a long-acting in vivo efficacy.     

1-[2-(2,4-二氯苯基)-4-烃氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑类化合物的合成及杀菌活性研究

2,4-二氯苯乙酮经溴化得ω-溴-2,4-二氯苯乙酮,该化合物与丙三醇在对甲基苯磺酸催化下脱水,得2-(2,4-二氯苯基)-2-溴甲基-4-羟甲基-1,3-二氧戊环,该中间体与苯甲酰氯在常温下反应,合成了2-(2,4-二氯苯基)-2-溴甲基-4-苯甲酰氧基甲基-1,3-二氧戊环,然后与三氮唑钠盐在130℃反应36 h,之后在碱性条件下水解,获得1-[2-(2,4-二氯苯基)-4-羟甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑,再以吡啶为缚酸剂继续与甲磺酰氯反应,合成了1-[2-(2,4-二氯苯基)-4-甲磺酰氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑,最后在碱性条件下,与12个不同结构的酚缩合成标题化合物1-[2-(2,4-二氯苯基)-4-烃氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑。标题化合物的结构用GC-MS、FTIR进行了表证。生物活性实验结果表明,12个标题化合物对水稻稻瘟病菌的抑菌率均在88.0%以上,其中,1-[2-(2,4-二氯苯基)-4-间甲基苯氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑达100%。1-[2-(2,4-二氯苯基)-4-苯氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑和1-[2-(2,4-二氯苯基)-4-对硝基苯氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑对油菜菌核病菌的抑菌率分别为100%和97.8%;1-[2-(2,4-二氯苯基)-4-间甲基苯氧基甲基-1,3-二氧戊环-2-基]甲基-1H-1,2,4-三氮唑对小麦赤霉病菌的抑制活性为91.2%。     

Highly potent fluorescence-tagged nonimidazole histamine H3 receptor ligands

Different (3-phenoxypropyl)piperidine derivatives have been coupled to fluorescent moieties (5-dimethylaminonaphthalene-1-sulfonyl, carbazol-9-ylcarbonyl, 2-cyanoisoindol-1-yl, 2-cyanobenzo[f]isoindol-1-yl, 2,4-dinitrobenzen-1-yl, 2,4-diaminophenyl, 7-nitrobenzofurazan-4-yl, 7-aminosulfonylbenzofurazan-4-yl, 4-methylcoumarin-6-yl) as novel histamine H(3) receptor ligands. They have been synthesised starting from piperidine in a few steps. The compounds display good to excellent histamine hH(3) receptor affinities with K(i) values ranging from 13.4 to 0.048 nM. Some of the new compounds belong to the most potent ligands known so far and may act as tools for identification and understanding of the binding site on the histamine H(3) receptor. In vivo screening on selected derivatives of Sanger's reagent showed antagonist potencies with ED(50) values from 7.9 to 0.39 mg kg(-1), p.o.