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A series of 2,3,4,9-tetrahydro-β-carboline tetrazole derivatives (14a–u) have been synthesized utilizing the Ugi multicomponent reaction and were identified as potential antileishmanial chemotypes. Most of the screened derivatives exhibited significant in vitro activity against the promastigote (IC50 from 0.59 ± 0.35 to 31 ± 1.27 μM) and intracellular amastigote forms (IC50 from 1.57 ± 0.12 to 17.6 ± 0.2 μM) of L. donovani, and their activity is comparable with standard drugs miltefosine and sodium stibogluconate. The most active compound 14t was further studied in vivo against the L. donovani/golden hamster model at a dose of 50 mg kg−1 through the intraperitoneal route for 5 consecutive days, which displayed 75.04 ± 7.28% inhibition of splenic parasite burden. Pharmacokinetics of compound 14t was studied in the golden Syrian hamster, and following a 50 mg kg−1 oral dose, the compound was detected in hamster serum for up to 24 h. It exhibited a large volume of distribution (651.8 L kg−1), high clearance (43.2 L h−1 kg−1) and long mean residence time (10 h).

A novel series of highly diverse indole-2-carboxamides was synthesized utilizing the isocyanide based multicomponent reaction (IMCR)-post modification approach and were identified as potential antileishmanial chemotype. Among the synthesized 18 analogues, 12 analogues exhibited better antileishmanial activity against intracellular amastigotes form of Leishmania donovani (IC50 values of 0.6-7.5 μM) as compared to standard drugs miltefosine and sodium stibogluconate. The compounds were also non-toxic towards Vero cells. Compounds 2b, 2m and 2p with significant in vitro activity were then evaluated for their in vivo efficacy following intraperitoneal route. These three compounds at a concentration of 50 mg/kg/day for 5 consecutive days showed 70.0, 63.5 and 63.4% inhibition of Leishmania amastigotes, respectively at day 7 post treatment in hamster model of visceral leishmaniasis.

A one-pot domino multicomponent reaction for the rapid, integrated and versatile synthesis of highly functionalized β-carbolinones (9a–9ab) and indolo-pyrazinones (10a–10ab) has been established. The reaction involves an Ugi-four component reaction of indole 2-carboxylic acid (1 or 16a–c), aryl or alkyl aldehyde (6a–p), isocyanide (3a–e), and aminoacetaldehyde dimethyl acetal (7) followed by in situ acid-mediated deprotection/activation/electrophilic cyclisation/and aromatisation. The products were obtained from Ugi adducts in good to excellent yield within short periods of 20–30 min at room temperature (35 °C). The potential of the methodology is proved by development of a diverse library of heterocyclic compounds with point and skeletal diversity. Moreover, the synthesis has also been accomplished using N-substituted derivatives of indole 2-carboxylic acid that delivers highly diverse N-substituted β-carbolinone (18a–l) heterocycles of medicinal importance.

β-Carbolines have been assessed for osteoclastogenesis. However, their effect on osteoblasts during estrogen deficiency is still unclear. Here, a series of novel piperazine and tetrazole tag β-carbolines have been synthesized and examined for osteoblast differentiation in vitro. In vitro data suggest that compound 8g is the most promising osteoblast differentiating agent that was evaluated for in vivo studies. Compound 8g promoted osteoblast mineralization, stimulated Runx2, BMP-2 and OCN expression levels, increased BrdU incorporation and inhibited generation of free radicals as well as nitric oxide. Since a piperazine group is involved in bone repair activity and β-carboline in IκB kinase (IKK) inhibition, compound 8g inhibited tumor necrosis factor α (TNFα) directed IκBα phosphorylation, preventing nuclear translocation of NF-κB thereby alleviating osteoblast apoptosis. In vivo studies show that compound 8g was able to restore estrogen deficiency-induced bone loss in ovariectomized rats without any toxicity, thus signifying its potential in bone-protection chemotherapy under postmenopausal conditions.

A novel and robust route for the synthesis of diversely substituted isoindoline skeletons through a ligand-free Pd-catalyzed cascade consisting of isocyanide insertion into Ugi-tetrazole has been developed. The tetrazole precursor is prepared in one step by the Ugi-four component reaction. The reaction proceeds smoothly under mild conditions with high efficiency. This chemistry is simple, economical, and is believed to be the key step during the synthesis of significant pharmaceuticals.

Trypanothione reductase (TR) is a vital enzyme in the trypanothione based redox metabolism of trypanosomatid parasites. It is one of the few chemically validated targets for Leishmania. Herein, we report the synthesis of novel β-carboline–quinazolinone hybrids that are able to inhibit Leishmania donovani TR (LdTR) and subsequently inhibit cell growth. A molecular modeling approach based on docking studies and subsequent binding free energy estimation was performed in the active site of LdTR to understand their possible binding sites. With the enzymatic assay on LdTR with compounds, we were able to identify six hit compounds (8j–8o) that were all found to be the competitive inhibitors of TR with Ki in the range of 0.8–9.2 μM. The whole-cell screening assay highlighted the analogues 8k, 8l and 8n as the most active compounds with IC50 of 4.4, 6.0 and 4.3 μM, respectively, along with an adequate selectivity index (SI) of >91, 36 and 24, respectively.

An expedient construction of tetrahydro-β-carbolinediketopiperazine ring systems, which are present in various indole alkaloids, is documented. The synthetic strategy proceeds through a Pictet–Spengler reaction followed by an Ugi-4CR and deprotection-cyclization reactions. This is the first report of a Pre-Ugi multicomponent reaction modification using 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-1-carboxylic acid as the acidic partner. This novel approach provides highly diverse reconstructions of novel tetrahydro-β-carbolinediketopiperazine derivatives, which can also be used as privileged structures in medicinal chemistry.

In search of potential therapeutics for tuberculosis, we describe here the synthesis and in vitro antitubercular activity of a novel series of thiazolone piperazine tetrazole derivatives. Among all the synthesized derivatives, four compounds (10, 14, 20 and 33) exhibited more potent activity (MIC = 3.08, 3.01, 2.62 and 2.51 μM) than ethambutol (MIC = 9.78 μM) and pyrazinamide (MIC = 101.53 μM) against Mycobacterium tuberculosis. Furthermore, they displayed no toxicity against Vero cells (C1008) and mouse bone marrow derived macrophages (MBMDMɸ). These investigated analogues have emerged as possible lead molecule to enlarge the scope of the study.

A series of novel 4-aminoquinolinyl and 9-anilinoacridinyl Schiff base hydrazones have been synthesized and evaluated for their antimalarial activity. All compounds were evaluated in vitro for their antimalarial activity against chloroquine-sensitive strain 3D7 and the chloroquine-resistant K1 strain of Plasmodium falciparum and for cytotoxicity toward Vero cells. Compounds 17, 20, and 21 displayed good activity against the 3D7 strain with IC50 values ranging from 19.69 to 25.38 nm. Moreover, compounds 16, 17, 21, 24, 32, and 33 exhibited excellent activities (21.64-54.26 nm) against K1 strain and several compounds displayed β-hematin inhibitory activity, suggesting that they act on the heme crystallization process such as CQ. Compounds were also found to be non-toxic with good selectivity index.

A metal-free facile and efficient two-step synthetic protocol for the preparation of 1,4-benzoxazepine-5(2H)-one derivatives has been developed. The protocol involves Ugi reaction followed by K2CO3 mediated highly regioselective 7-exo-dig intramolecular cyclization of less-nucleophilic oxygen with the pendant alkyne moiety of an Ugi-propargyl precursor to afford the 1,4-benzoxazepine-5(2H)-one derivatives in good to excellent yields.

An efficient and mild protocol for rapid access to N-fused polyheterocycles via Pictet–Spengler type 6-endo cyclization using cyanuric chloride in an aqueous reaction medium has been developed. The protocol was successfully applied to a wide range of compounds including aryl/heteroaryl aldehydes (8a–o), ketones (10a–e), an electron-rich metallocene aldehyde (8e) and indoline-2,3-diones (12a–c) using cyanuric chloride (15–20 mol%) with tetra-n-butylammonium bromide (TBAB) (2.0 eq.) as an additive at 80–90 °C to give a good to excellent yield (66–92%) of polyheterocycles. Some of the synthesized compounds were found to exhibit antiplasmodial activity against chloroquine-sensitive (CQ-S) 3D7 and chloroquine-resistant (CQ-R) K1 strains of Plasmodium falciparum.

An unusual potassium carbonate mediated transformation of 2,3-dihydroquinazolinone by a one-pot operation is reported under mild conditions. In addition, it is interesting to report the regioselective transformation of 3-(2-bromophenyl)-2-isopropyl-2,3-dihydroquinazolin-4(1H)-one from compound 16 .

The World Health Organization has classified the leishmaniasis as a major tropical disease. The discovery of new compounds for leishmaniasis is therefore a pressing concern for the anti-infective research program. We have synthesized 19 compounds of triazine dimers as novel antileishmanial agents. Most of the synthesized derivatives exhibited better activity against intracellular amastigotes (IC50 ranging from 0.77 to 10.32 μM) than the control, pentamidine (IC50 = 13.68 μM), and are not toxic to Vero cells. Compounds 14 and 15 showed significant in vivo inhibition of 74.41% and 62.64%, respectively, in L. donovani/hamster model. Moreover, expansion of Th1-type and suppression of Th2-type immune responses proved that compound 14 stimulates mouse macrophages to prevent the progression of leishmania parasite. The molecular docking studies involving PTR1 protein PDB further validated the concepts involved in the design of these compounds. Among the investigated analogues, compound 14 has emerged as the potential one to enlarge the scope of the study.

The dimethylamino functionality is generally introduced onto the 3,5-dihydro-4H-imidazol-4-one skeleton by treatment of a halogenated derivative with low-boiling dimethylamine at a high temperature and pressure. The corresponding aliphatic ethers are usually prepared by Williamson ether synthesis, but the available transition-metal-catalyzed methods require highly toxic reagents (such as dimethyl sulfate or methyl halides) and expensive metal catalysts, and they entail harsh reaction conditions and complex workups. A simple and efficient method is described for base-mediated­ desulfitative dimethylamination, oxidation, or etherification at the C2-position of the 2-(methylsulfanyl)-3,5-dihydro-4H-imidazol-4-one scaffold by using potassium carbonate and aqueous N,N-dimethylformamide or an aliphatic alcohol.

Aza-fused polycyclic indolediketopiperazine alkaloids are of potential interest due to their broad range of biological activities. Traditionally, a number of methods have been used to generate N-fused polycyclic indolediketopiperazine skeletons, but the need to develop novel, concise methods with which to modify the substitution pattern continues. Herein, we describe the two-step formation of N-fused polycyclic indolediketopiperazine alkaloid analogues by the application of the Ugi four-component reaction with tandem deprotection, cyclization and Pictet–Spengler reaction.

The high potential of quinazolinone containing natural products and their derivatives in medicinal chemistry led us to discover four novel series of 53 compounds of quinazolinone based on the concept of molecular hybridization. Most of the synthesized analogues exhibited potent leishmanicidal activity against intracellular amastigotes (IC50 from 0.65 ± 0.2 to 7.76 ± 2.1 μM) as compared to miltefosine (IC50 = 8.4 ± 2.1 μM) and nontoxic toward the J-774A.1 cell line and Vero cells. Moreover, activation of Th1 type and suppression of Th2 type immune responses and induction in nitric oxide generation proved that 8a and 8g induce murine macrophages to prevent survival of parasites. Compounds 8a and 8g exhibited significant in vivo inhibition of parasite 73.15 ± 12.69% and 80.93 ± 10.50% against Leishmania donovani /hamster model. Our results indicate that compounds 8a, 8g, and 9f represent a new structural lead for this serious and neglected disease.

The present work highlights a synthetic approach to the diverse isoindolinone derivatives using Ugi-4CR followed by a Cu-catalyzed deamidative C–C coupling reaction. This two-step sequence tolerates a broad range of amines, aldehydes, and isocyanides as starting materials for Ugi-4CR products to provide medicinally relevant isoindolinone derivatives in moderate to good yields.

We have reported a microwave-assisted, ligand-free Pd-catalyzed domino C–C/C–N coupling reaction to construct diverse isoindolinone derivatives using amides and isocyanides as coupling partners. This strategy provides isoindolinone derivatives in moderate to good yield and high stereoselectivity. A broad range of amides has been tolerated and there is no need for extra-dry conditions in this reaction protocol, which offered highly diverse products and easy handling of the reaction.

The first protocol for the synthesis of perspicamide A and related diverse analogues has been developed from economical and readily available starting materials. Furthermore, a few synthesized analogues, 24a, 24b, 24c, 24d, and 24l, exhibited potent activity against Leishmania donovani with IC(50) values ranging from 3.75 to 10.37 μM and a selectivity index (SI) ranging from 9.58 to 53.12, which is improved compared to the standard drug Miltefosine (IC(50) 12.4 μM and SI 4.1).

Mouse double minute 2 (MDM2) protein functionally inactivates the tumor suppressor p53 in human cancer. Conventional MDM2 inhibitors provide limited clinical application as they interfere only with the MDM2-p53 interaction to release p53 from MDM2 sequestration but do not prevent activated p53 from transcriptionally inducing MDM2 expression. Here, we report a rationally synthesized chalcone-based pyrido[ b ]indole, CPI-7c, as a unique small-molecule inhibitor of MDM2, which not only inhibited MDM2-p53 interaction but also promoted MDM2 degradation. CPI-7c bound to both RING and N-terminal domains of MDM2 to promote its ubiquitin-mediated degradation and p53 stabilization. CPI-7c-induced p53 directly recruited to the promoters of DR4 and DR5 genes and enhanced their expression, resulting in sensitization of TNF-related apoptosis-inducing ligand (TRAIL)-resistant cancer cells toward TRAIL-induced apoptosis. Collectively, we identified CPI-7c as a novel small-molecule inhibitor of MDM2 with a unique two-prong mechanism of action that sensitized TRAIL-resistant cancer cells to apoptosis by modulating the MDM2-p53-DR4/DR5 pathway.

In this communication we report a serendipitously discovered hybrid molecule 1, combining fragment of 3 (an in vivo active antileishmanial molecule) with H2S donor moiety (known for bimodal behavior of cytoprotection and apoptosis), as antileishmanial agent. Compound 1 suppresses 99.82% parasitemia of L. donovani infected macrophages at 12.5 μg/ml without even deforming them (CC50 > 100 μg/ml). This compound appears cytotoxic for intracellular amastigotes while cytoprotective to host macrophages. The concept can be utilized to develop high therapeutic index NCE (New Chemical Entities) for other macrophage mediated diseases like tuberculosis and cancer.

An expedient construction of tetrahydro-β-carbolinediketopiperazine ring systems, which are present in various indole alkaloids, is documented. The synthetic strategy proceeds through a Pictet–Spengler reaction followed by an Ugi-4CR and deprotection-cyclization reactions. This is the first report of a Pre-Ugi multicomponent reaction modification using 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-1-carboxylic acid as the acidic partner. This novel approach provides highly diverse reconstructions of novel tetrahydro-β-carbolinediketopiperazine derivatives, which can also be used as privileged structures in medicinal chemistry.

For the first time, an efficient method for the synthesis of tetrazole-isoindoline via palladium-catalyzed cyclization with isocyanide insertion is demonstrated.

An efficient approach for the synthesis of indole- and pyrrole-fused diketopiperazines has been developed. This protocol involves the Ugi four-component reaction (U-4CR) followed by an intramolecular cyclization of the Ugi products at room temperature to afford the desired products in good to excellent yields. In addition, it is interesting to report the subsequent regioselective ring-opening of diketopiperazine unit occurring via an intermolecular transamidation reaction under mild condition, resulting in the formation of highly functionalized indole-2-carboxamides and pyrrole-2-carboxamides.

A novel green and energy-efficient synthesis of 2,3-dihydro/spiroquinazolin-4(1H)-ones via three-component cyclo­condensation reaction involving isatoic anhydride, amines and aldehydes/ketones utilizing recyclable tartaric acid–SDS catalyst system has been achieved. With simple requirements of mechanical stirring or mechanochemical activation at room temperature and one of the shortest reported times as of yet, it is a significant improvement on previously described methods for the synthesis of such compounds. Moreover the catalyst system can also be efficiently applied in large-scale reactions which indicates the potential for applications in industry.

A novel ligand-free palladium-catalyzed cascade reaction for the synthesis of highly diverse isoquinolin-1(2H)-one derivatives from isocyanide and amide precursors synthesized by Ugi-MCR has been developed. A broad variety of acids, amines, and isocyanides were used as starting materials for Ugi-MCR leading to various amide precursors, which in turn provided entry into diverse isoquinolin-1(2H)-one derivatives. The reaction proceeds through tandem isocyanide insertion with intramolecular cyclization followed by a Mazurciewitcz-Ganesan type sequence to provide isoquinoline-1(2H)-one derivatives in moderate to good yields.

Several diversity-oriented syntheses of N-fused polycyclic heterocycles have been demonstrated but most of them are based on point diversity within the same library and usually involve time-consuming sequential multistep syntheses, which also suffer from low yields and/or poor precursor scopes. We have developed a new strategy for the syntheses of skeletal diverse N-fused polycyclic compounds via an Ugi-type MCR followed by a CuI-catalyzed coupling reaction or tandem Pictet-Spengler reaction. This two-step sequence provides eight distinct skeleton of fused {6-5-5-6}, {5-5-5-6}, {6-5-6-6}, and {5-5-6-6} ring systems that have applications in medicinal chemistry and chemical genetics too.

Analogues of a novel class of hybrid 4-anilinoquinoline triazines have been synthesized with the aim of identifying the compounds with improved antimalarial activity preserving the potency of parent drug chloroquine (CQ). All the synthesized molecules were evaluated in vitro for their antimalarial activity against chloroquine-sensitive 3D7 and chloroquine-resistant K1 strains of P. falciparum. Molecules were also screened for their cytotoxicity towards VERO cell line. Sixteen compounds (17, 19, 26, 27, 29, 31, 32, 33, 35, 36, 37, 39, 40, 49, 50, and 52) exhibited excellent antimalarial activity with IC50 values ranging from 1.36–4.63 ng ml−1 and were also found to be nontoxic with good selectivity index. In silico activity prediction as well as enzyme inhibitory activity against P. falciparumtransketolase reveals that the molecules are also good inhibitors of the enzymeP. falciparumtransketolase. The compound 52 showed good in vivo activity by oral route and resulted in survival of 3 out of 5 mice till day 28.

A new and efficient protocol is presented for selective and direct oxidative conversion of phenylmethylene-2-thiohydantoins to corresponding hydantoins. It involves the use of SnCl2.2H2O, which oxidatively desulfurizes the phenylmethylene-2-thiohydantoins to their corresponding hydantoin analogues in good to excellent yields while all other 2-thiohydantoins remain unaffected. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

To commemorate 2011 as the International Year of Chemistry, the Indian Society of Chemists and Biologists organized its 15th International Conference on ‘Bridging Gaps in Discovery and Development: Chemical and Biological Sciences for Affordable Health, Wellness and Sustainability’ at Hotel Grand Bhagwati, in association with Saurashtra University, Rajkot, India. Anamik Shah, President of the Indian Society of Chemists and Biologists, was organizing secretary of the conference. Nicole Moreau, President of the International Union of Pure and Applied Chemistry and Secretary General of the Comité National de la Chimie, National Centre for Scientific Research France, was chief guest of the function. The four-day scientific program included 52 plenary lectures, 24 invited lectures by eminent scientists in the field and 12 oral presentations. A total of 317 posters were presented by young scientists and PhD students in three different poster sessions. Approximately 750 delegates from India, the USA, UK, France, Switzerland, Germany, Austria, Belgium, Sweden, Japan and other countries attended the conference. The majority of the speakers gave presentations related to their current projects and areas of interest and many of the talks covered synthesis, structure–activity relationships, current trends in medicinal chemistry and drug research.

A series of novel 8-fluoro Norfloxacin derivatives and the hybrids of its piperazinyl derivatives incorporated with 1,3,5-triazine and pyrimidine were synthesized. All the above compounds were evaluated for their antibacterial activity against Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus and methicillin & vancomycin-resistant S. aureus. Among all, compounds having Morpholine, N-methyl/phenyl/benzyl/pyrimidinyl piperazines and n-butylamine substitution at C-7 position, have shown increased potency in comparison to norfloxacin and ciprofloxacin.

A novel class of hybrid 4-anilinoquinoline triazines have been synthesized and evaluated in vitro for their antimalarial activity against CQ-sensitive 3D7 strain of P. falciparum as well as for their cytotoxicity toward VERO cell line. Five compounds (19, 20, 23, 41 and 45) exhibited the antimalarial potency superior to CQ. Compounds 14 and 16 were found to be orally active at a dose of 100 mg/kg×4 days against CQ-resistant strain of P. yoelii. Inhibition of β-hematin formation assay and molecular docking study has been conducted in order to gain insight into the mechanism of action of proposed targets for the 4-anilinoquinoline and triazine moiety of the hybrid compounds.

A series of indolylglyoxylamide derivatives have been synthesized and evaluated in vitro against amastigote form of Leishmania donovani. Compound 8c has been identified as the most active analog of the series with IC(50) value of 5.17μM and SI value of 31.48, and is several folds more potent than the standard drugs sodium stilbogluconate and pentamidine.

A series of 2-(pyrimidin-2-yl)-1-phenyl-2,3,4,9-tetrahydro-1 H -β-carboline derivatives has been synthesized and evaluated for antileishmanial activity against Leishmania donovani . Compound 8 exhibited best antileishmanial activity with IC 50 value of 1.93 μg/ml against amastigotes, high selectivity index, and was more active than reference drugs sodium stilbogluconate and pentamidine.

A series of eighty one 2,4,6-trisubstituted-1,3,5-triazines were synthesized and evaluated in vitro for the growth inhibition of Mycobacterium tuberculosis H37Rv. Fifteen compounds from this series exhibited good to moderate activity with an MIC in the range 1.56–3.12 μg/mL and most of them were found to be nontoxic against VERO cells and MBMDMQs (mouse bone marrow derived macrophages). This is for the first time that 2,4,6-trisubstituted-1,3,5-triazines were identified as a potent inhibitors of M . tuberculosis H37Rv.

A series of [1,2,4]triazino[5,6-b]indol-3-ylthio-1,3,5-triazines and [1,2,4]triazino[5,6-b]indol-3-ylthio-pyrimidines were synthesized and screened for their in vitro antileishmanial activity against Leishmania donovani. Among all, 8 compounds have shown more than 90% inhibition against promastigotes and IC50 in the range of 4.01-57.78 microM against amastigotes. Compound 5, a triazino[5,6-b]indol-3-ylthio-1,3,5-triazine derivative was found to be the most active and least toxic with 20- & 10-fold more selectivity (S.I.=56.61) as compared to that of standard drugs pentamidine and sodium stibogluconate (SSG), respectively.

There is challenge and urgency to synthesize cost-effective chemotherapeutic agents for treatment of malaria after the widespread development of resistance to CQ. In the present study, we synthesized a new series of hybrid 9-anilinoacridine triazines using the cheap chemicals 6,9-dichloro-2-methoxy acridine and cyanuric chloride. The series of new hybrid 9-anilinoacridine triazines were evaluated in vitro for their antimalarial activity against CQ-sensitive 3D7 strain of Plasmodium falciparum and their cytotoxicity were determined on VERO cell line. Of the evaluated compounds, two compounds 17 (IC(50)=4.21 nM) and 22 (IC(50)=4.27 nM) displayed two times higher potency than CQ (IC(50)=8.15 nM). Most of the compounds showed fairly high selectivity index. The compounds 13 and 29 displayed >96.59% and 98.73% suppression, respectively, orally against N-67 strain of Plasmodium yoelii in swiss mice at dose 100 mg/kg for four days.

In an attempt to synthesize pentamidine-aplysinopsin hybrid molecule 25, a lead molecule 8 (containing Z-configured aplysinopsin moiety) was identified for antileishmanial activity. Optimization of lead 8 provided 24 (containing E-configured aplysinopsin) possessing 10 times more activity and 401-fold less toxicity than the drug pentamidine in cell based assays. Synthesis of 24 was possible, surprisingly, because of two innate reactivities of indole-3-carbaldehyde which provided it in diastereo- and regio-selectively pure form without recourse to the long reaction pathway.

Frequency of malaria and its resistance to chemotherapeutic options are emerging rapidly. To counter this problem, a series of 4-aminoquinolines having oxalamide and triazine functionalities in the side chain were synthesized and screened for their antimalarial activities. Triazine derivative 48 found to be the most active against CQ sensitive strain 3D7 of Plasmodium falciparum in an in vitro assay with an IC50 of 5.23 ng/mL and oxalamide derivative 13 showed an in vivo suppression of 70.45% on day 4 against CQ resistant strain N-67 of Plasmodium yoelii.

A series of 2,4,6-trisubstituted pyrimidines and 1,3,5-triazines have been synthesized and screened for their in vitro and in vivo antileishmanial activity against Leishmania donovani. Among all, 14 compounds have shown promising inhibition of 80-100% at 10 microg/ml against promastigotes and IC(50) in the range of 0.89-9.68 microg/ml against amastigotes. Three compounds 13, 32 and 33 with good selectivity index (S.I.) were screened for their in vivo activity in golden hamsters (Mesocricetus auratus) infected with MHOM/IN/80/Dd(8) strain of L. donovani and have shown moderate in vivo inhibition of 48-56% at a dose of 50 mg/kg x 5, i.p. route for 5 days.

In search of new 4-aminoquinolines which are not recognized by CQR mechanism, thiourea, thiazolidinedione and thioparabanic acid derivatives of 4-aminoquinoline were synthesized and screened for their antimalarial activities. Thiourea derivative 3 found to be the most active against CQ sensitive strain 3D7 of Plasmodium falciparum in an in vitro model with an IC50 of 6.07 ng/mL and also showed an in vivo suppression of 99.27% on day 4 against CQ resistant strain N-67 of Plasmodium yoelii.

The emergence and rapid spread of chloroquine resistant strains of Plasmodium falciparum has dramatically reduced the chemotherapeutic options. Towards this goal, a series of new class of hybrid 4-aminoquinoline triazines were synthesized and screened against CQ sensitive strain 3D7 of P. falciparum in an in vitro model. Compounds 65 and 69 exhibited more than 99% suppression on day 4 and on day 6 post treatment, compound 69 showed impressive 99.11% suppression against CQ resistant strain N-67 of P. yoelii in an in vivo assay.

A novel series of 4-amino-5-cyano-2, 6-disubstituted pyrimidines have been synthesized and evaluated for their in vitro antifilarial DNA topoisomerase II activity against filarial parasite Setaria Cervi. In particular compounds bearing 4-chloro-phenyl substitutent at position-6, exhibited strong inhibition at 40 microg/mL and 5 microg/mL concentration. The present study based on the biological results obtained, suggests that the nature of substitutent at position-4 in the phenyl ring directly affects DNA topoisomerase II inhibitory activity. Most of the compounds have shown better topoisomerase II inhibitory activity than the standard antifilarial drug (DEC) and the topoisomerase II inhibitors (Novobiocin, Nalidixic acid).

The chemoselective S-alkylation of 2-thiohydantoins is reported. The methodology involves the use of alkyl orthoformates (trimethyl and triethyl) as alkylating agents, which in the presence of Ac2O and ZnCl2 chemoselectively alkylate the thio group whilst other nucleophilic groups present in the thiohydantoins are acetylated simultaneously in moderate to high yields. A plausible mechanism for this reaction is delineated.

The marine organisms are a rich source of varied natural products with unique functionality. Marine natural products chemistry has undergone an explosive growth during the past three decades. A variety of natural products of new molecular structures with diverse biological activities have been reported from marine flora and fauna, thus ensuring motivation in the search of newer natural products. The bis and trisindole alkaloids are a class of marine natural products that show unique promise in the development of new drug leads. 3-hydroxy staurosporine 51, an indolo carbazole having powerful antiproliferative activity. Hamacanthin A 1 and B 2, pyrazinone alkaloids have significant antimicrobial activity. Coscinamides 60-62 and Chondriamides 63-65 an indolic enamides which have anti-HIV and cytotoxic activity respectively. Gelluisine A 66 and B 67, trisindole alkaloids have strong anti-serotonin activity and strong affinity with somatostatin and neuropeptide Y receptors in receptor-binding assays. This report reviews the literature on these alkaloids of marine origin and highlights the isolation, structure, latest synthesis and specific biological activities including cytotoxicity, antiviral, antiparasitic, serotonin antagonism and other pharmacological activities of sixty-nine bis and trisindole alkaloids.

Trypanothione reductase (TR) is essential for the survival of the protozoan parasite Leishmania, and, therefore, offers a promising target for the development of selective new drugs against Leishma...

An efficient and mild protocol for rapid access to N-fused polyheterocycles via Pictet–Spengler type 6-endo cyclization using cyanuric chloride in an aqueous reaction medium has been developed. The protocol was successfully applied to a wide range of compounds including aryl/heteroaryl aldehydes (8a–o), ketones (10a–e), an electron-rich metallocene aldehyde (8e) and indoline-2,3-diones (12a–c) using cyanuric chloride (15–20 mol%) with tetra-n-butylammonium bromide (TBAB) (2.0 eq.) as an additive at 80–90 °C to give a good to excellent yield (66–92%) of polyheterocycles. Some of the synthesized compounds were found to exhibit antiplasmodial activity against chloroquine-sensitive (CQ-S) 3D7 and chloroquine-resistant (CQ-R) K1 strains of Plasmodium falciparum.