Synthesis and serotonergic activity of substituted 2, N-benzylcarboxamido-5-(2-ethyl-1-dioxoimidazolidinyl)-N, N-dimethyltryptamine derivatives: novel antagonists for the vascular 5-HT(1B)-like receptor

Indole bearing thiadiazole analogs: synthesis, β-glucuronidase inhibition and molecular docking study

Indole based thiadiazole derivatives (1-22) have synthesized, characterized by NMR and HREI-MS and evaluated for β-Glucuronidase inhibition. All compounds showed outstanding β-glucuronidase activity with IC50 values ranging between 0.5 ± 0.08 to 38.9 ± 0.8 µM when compared with standard d-saccharic acid 1,4 lactone (IC50 value of 48.1 ± 1.2 µM). The compound 6, a 2,3-dihydroxy analog was found the most potent among the series with IC50 value 0.5 ± 0.08 µM. Structure activity relationship has been established for all compounds. To confirm the binding interactions of these newly synthesized compounds, molecular docking study have been carried out which reveal that these compounds established stronger hydrogen bonding networks with active site residues.

Tetrazoles via Multicomponent Reactions

Tetrazole derivatives are a prime class of heterocycles, very important to medicinal chemistry and drug design due to not only their bioisosterism to carboxylic acid and amide moieties but also to their metabolic stability and other beneficial physicochemical properties. Although more than 20 FDA-approved drugs contain 1 H- or 2 H-tetrazole substituents, their exact binding mode, structural biology, 3D conformations, and in general their chemical behavior is not fully understood. Importantly, multicomponent reaction (MCR) chemistry offers convergent access to multiple tetrazole scaffolds providing the three important elements of novelty, diversity, and complexity, yet MCR pathways to tetrazoles are far from completely explored. Here, we review the use of multicomponent reactions for the preparation of substituted tetrazole derivatives. We highlight specific applications and general trends holding therein and discuss synthetic approaches and their value by analyzing scope and limitations, and also enlighten their receptor binding mode. Finally, we estimated the prospects of further research in this field.

Design, synthesis and diversification of natural product-inspired hydantoin-fused tetrahydroazepino indoles

A facile and efficient synthesis of novel oxo, thio and seleno hydantoin fused tetrahydroazepino [4,5-b]indoles was reported.

Molecular structure, tautomeric stability, protonation and deprotonation effects, vibrational, NMR and NBO analyses of 2,4-Dioxoimidazolidine-5-acetic acid (DOIAA) by quantum chemical calculations

This study represents the conformation, tautomeric stability, protonation and deprotonation effects, vibrational, electronic, NBO and NMR aspects of 2,4-Dioxoimidazolidine-5-acetic acid (DOIAA). Theoretical calculations were performed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets. Tautomerism and the effect of solvent on the tautomeric equilibria in the gas phase and in different solvents were studied. The protonation and deprotonation effects on the reactivity and conformations of DOIAA were investigated. Electronic transitions were also studied and the most prominent transition corresponds to π→π*. Natural bond orbital (NBO) analysis was also carried out to find the intramolecular interactions and their stabilization energy. In DOIAA, the interaction between the lone pair donor orbital (n(LP1N5)) and the acceptor antibonding orbital π*(C6O7) reveals the strong stabilization energy of 224.9 kJ mol(-1). Molecular electrostatic potential (MEP) was calculated to predict the reactive sites of the title compound. The NMR results indicated that the observed chemical shifts for NH, COOH protons of DOIAA not only depend on the structure of the molecule being studied but also on the nature of the solvent, concentration of the sample and the presence of the other exchangeable protons.

3-(4-Bromo-phen-yl)-1-butyl-5-[1-(2-chloro-6-methyl-phen-yl)-1H-tetra-zol-5-yl]imidazolidine-2,4-dione

In the title mol-ecule, C21H20BrClN6O2, the chloro-substituted benzene ring forms a dihedral angle of 77.84 (7)° with the tetra-zole ring and the bromo-substituted ring forms a dihedral angle of 43.95 (6)° with the imidazole ring. The dihedral angle between the tetra-zole and imidazole rings is 67.42 (8)°. The terminal methyl group of the butyl substituent is disordered over two sets of sites, with refined occupancies 0.67 (3) and 0.33 (3). In the crystal, there is a short Br⋯N contact of 3.183 (2) Å.

Synthesis of 1,3,5-trisubstituted hydantoins by regiospecific domino condensation/aza-Michael/O-->N acyl migration of carbodiimides with activated alpha,beta-unsaturated carboxylic acids

[reaction: see text] Carbodiimides and suitably activated alpha,beta-unsaturated carboxylic acids react effectively to afford a vast array of 1,3,5-trisubstituted hydantoins by means of a regiospecific domino condensation/aza-Michael/N-->O acyl migration. The reaction works well in very mild conditions (20 degrees C, dichloromethane) with fumaric acid derivatives bearing an electron-withdrawing group in the beta position. Good results have been obtained also with less activated substrates bearing only one electron-withdrawing group in the beta position, using more polar solvents (acetonitrile, DMF), and in the presence of a base (2,4,6-trimethylpyridine). Reactions with asymmetric carbodiimides are generally highly chemo- and regioselective, giving rise to the formation of a single regioisomeric hydantoin. However, asymmetric carbodiimides bearing one alkyl group and one aryl group can produce variable amounts of N-acylurea byproducts. The latter could be easily recovered and transformed into the corresponding hydantoins. A detailed study of the influence of key reaction parameters such as solvent, base, and structure of the reactants on the reaction outcome and mechanism is presented. This methodology is particularly convenient for the synthesis of trifluoromethyl-substituted hydantoins, which could be interesting as bioactive compounds in medicinal chemistry, as well as precursors of the corresponding alpha-amino acids.

Synthesis of photoswitchable amino acids based on azobenzene chromophores: building blocks with potential for photoresponsive biomaterials

Three novel derivatives of azobenzene substituted amino acids have been synthesized. The compounds may serve as photoswitchable building blocks in the synthesis of bicyclic peptides or peptide strands interconnected with a photoisomerizable group.

Synthesis and serotonergic activity of variously substituted (3-amido)phenylpiperazine derivatives and benzothiophene-4-piperazine derivatives: novel antagonists for the vascular 5-HT1B receptor

The synthesis and vascular 5-HT(1B) receptor activity of a novel series of substituted 3-amido phenylpiperazine and 4-(4-methyl-1-piperazinyl)-1-benzo[b]thiophene derivatives is described. Modifications to the amido linked sidechains of the 3-amidophenyl-piperazine derivatives and to the 2-sidechain of the 1-benzo[b]thiophene derivatives have been explored. Several compounds were identified which exhibited affinity at the vascular 5-HT(1B) receptor of pK(B) > 7.0. From the 3-amidophenyl-piperazine series, N-(4-(4-chlorophenyl)thiazol-2-yl-3-(4-methyl-1-piperazinyl)benzamide (30) and from the benzo[b]thiophene-4-piperazine series N-(2-ethylphenyl)-4-(4-methyl-1- piperazinyl)-1-benzo[b]thiophene-2-carboxamide (38) were identified as a highly potent, silent (as judged by the inability of angiotensin II to unmask 5-HT(1B) receptor mediated agonist activity in the rabbit femoral artery) and competitive vascular 5-HT(1B) receptor antagonist. The affinity of compounds from these two series of compounds for the vascular 5-HT(1B) receptor is discussed as well as a proposed mode of binding to the receptor pharmacophore.

Pyrazole derivatives as partial agonists for the nicotinic acid receptor

Nicotinic acid as a hypolipidemic agent appears unique due to its potential to increase HDL cholesterol levels to a greater extent than other drugs. However, it has some side effects, among which severe skin flushing is the most frequent and often limits patients' compliance. In a search for novel agonists for the recently identified and cloned G protein-coupled nicotinic acid receptor, we synthesized a series of substituted pyrazole-3-carboxylic acids that proved to have substantial affinity for this receptor. The affinities were measured by inhibition of [(3)H]nicotinic acid binding to rat spleen membranes. Potencies and intrinsic activities relative to nicotinic acid were determined by their effects on [(35)S]GTPgammaS binding to rat adipocyte and spleen membranes. Interestingly, most compounds were partial agonists. In particular, 2-diazabicyclo[3,3,0(4,8)]octa-3,8-diene-3-carboxylic acid (4c) and 5-propylpyrazole-3-carboxylic acid (4f) proved active with K(i) values of approximately 0.15 microM and EC(50) values of approximately 6 microM, while their intrinsic activity was only approximately 50% when compared to nicotinic acid. Even slightly more active was 5-butylpyrazole-3-carboxylic acid (4g) with a K(i) value of 0.072 microM, an EC(50) value of 4.12 microM, and a relative intrinsic activity of 75%. Of the aralkyl derivatives, 4q (5-(3-chlorobenzyl)pyrazole-3-carboxylic acid) was the most active with a relatively low intrinsic activity of 39%. Partial agonism of the pyrazole derivatives was confirmed by inhibition of G protein activation in response to nicotinic acid by these compounds. The pyrazoles both inhibited the maximum effect elicited by 100 microM nicotinic acid and concentration dependently shifted nicotinic acid concentration-response curves to the right, pointing to a competitive mechanism of action.

The aminobarbituric acid-hydantoin rearrangement

A general synthesis protocol for the generation of tri- and tetrasubstituted 5-carbamoylhydantoins is described. Starting from barbituric acids and following bromination and reaction with primary amines, 5-aminobarbituric acids 3a-s and 8 were prepared. Compounds 3 and 8 were subjected to different conditions of a base-catalyzed rearrangement reaction to yield the 1,5,5-trisubstituted hydantoins 4a-s and the 1,3,5,5-tetrasubstituted hydantoin 5c, respectively. Alkylation of 4a-s afforded 1,3,5,5-tetrasubstituted hydantoins 5a-h. Mechanisms that explain the transformation of corresponding aminobarbituric acids to hydantoins 4a-s and 5c were discussed in terms of the formation of ring-opened intermediates. Aminobarbituric acids 3a-s unsubstituted at position 3 underwent a ring contraction via intermediate isocyanates which were trapped by the amino function. A different mechanism involving a carbamate intermediate was concluded for conversion of the 1,3,5,5-tetrasubstituted aminobarbituric acid 8.

Design, synthesis, and evaluation of 6-carboxyalkyl and 6-phosphonoxyalkyl derivatives of 7-oxo-8-ribitylaminolumazines as inhibitors of riboflavin synthase and lumazine synthase

A series of 6-carboxyalkyl and 6-phosphonoxyalkyl derivatives of 7-oxo-8-D-ribityllumazine were synthesized as inhibitors of both Escherichia coli riboflavin synthase and Bacillus subtilis lumazine synthase. The compounds were designed to bind to both the ribitylpurine binding site and the phosphate binding site of lumazine synthase. In the carboxyalkyl series, maximum activity against both enzymes was observed with the 3'-carboxypropyl compound 22. Lengthening or shortening the chain linking the carboxyl group to the lumazine by one carbon resulted in decreased activity. In the phosphonoxyalkyl series, the 3'-phosphonoxypropyl compound 33 was more potent than the 4'-phosphonoxybutyl derivative 39 against lumazine synthase, but it was less potent against riboflavin synthase. Molecular modeling suggested that the terminal carboxyl group of 6-(3'-carboxypropyl)-7-oxo-8-D-ribityllumazine (22) may bind to the side chains of Arg127 and Lys135 of the enzyme. A hypothetical molecular model was also constructed for the binding of 6-(2'-carboxyethyl)-7-oxolumazine (15) in the active site of E. coli riboflavin synthase, which demonstrated that the active site could readily accommodate two molecules of the inhibitor.

Comparative HPLC enantioseparation of new chiral hydantoin derivatives on three different polysaccharide type chiral stationary phases

The enantioseparation of eighteen new chiral hydantoin derivatives was studied on three different polysaccharide type chiral stationary phases (CSP) Chiralpak AD, Chiralcel OD and Chiralcel OJ in the normal-phase HPLC mode. Chiralpak AD material exhibited the most universal chiral resolving ability and allowed the enantioseparation of 17 out of 18 compounds followed by Chiralcel OD (10 enantioseparations of 12 tested compounds) and Chiralcel OJ (eight enantioseparation from 13 tested analytes). Some complementary separations were observed and all of 18 compounds could be resolved at least with one of the three chiral CSP under the conditions of this study. With regard to the structure of the analytes, bulky electron rich substituents at C5 of the hydantoin nucleus appear to favor stereoselective interactions.

Discovery of 4-[3-(trans-3-dimethylaminocyclobutyl)-1H-indol-5-ylmethyl]-(4S)-oxazolidin-2-one (4991W93), a 5HT(1B/1D) receptor partial agonist and a potent inhibitor of electrically induced plasma extravasation

Utilizing a pharmacophoric model of binding of 3-(2-aminoethyl)indoles to 5HT(1B/1D) receptors, we identified the 3-aminocyclobutyl group as a potential ethylamine isostere. A novel multidimensional chemometric approach was used to predict the intrinsic activity (degree of agonism) at the receptor. A qualitative model for pharmacokinetic properties was then used to guide the synthesis toward molecules likely to have oral bioavailability in humans. A novel synthetic route to 3-(3-dimethylaminocyclobutyl)indoles was developed. Analogues showed generally lower intrinsic activity at 5HT(1B/1D) receptors than their ethylamine counterparts. 4-[3-(trans-3-Dimethylaminocyclobutyl)-1H-indol-5-ylmethyl]-(4S)-oxazolidin-2-one (4991W93, 1) was identified as a partial agonist against 5HT(1B/1D) receptors, with low intrinsic activity. This molecule also has significant activity against 5HT(1F) receptors but is selective over other 5HT receptors. In addition this compound was found to be an exceptionally potent inhibitor of electrically induced plasma extravasation. Compound 1 may have utility in the treatment and prophylaxis of migraine.