Sahil Sharma

Xanthine oxidase inhibitors: a patent survey

Introduction: Xanthine oxidase inhibitors are currently under scrutiny as attractive therapeutics for disorders such as hyperuricemia, gout, ulcers, cancer, ischemia, hypertension and oxidative damage. The fewer side effects of non-purine xanthine oxidase inhibitors, as compared to purine analogs, make them suitable for further research, which is evidenced by the fact that many articles and patents are now being published on them in the research domain. Areas covered: This review describes the patent literature covering both purine and non-purine analogs as xanthine oxidase inhibitors, up to December 2010, together with their recent highlights in pharmacology. Readers will gain an in-depth knowledge of patents covered and compounds discussed with their therapeutic use. Expert opinion: Several of the compounds which are discussed in this article have IC50 values which offer some advantages over existing molecules such as allopurinol. The available reports on X-ray crystal structures of xanthine oxidase will certainly be beneficial for the design and synthesis of novel xanthine oxidase inhibitors of diverse chemotypes.

Design and Synthesis of Aza‐Flavones as a New Class of Xanthine Oxidase Inhibitors

In an attempt to develop non‐purine‐based xanthine oxidase (XO) inhibitors, keeping in view the complications reported with the use of purine‐based XO inhibitors, the flavone framework (a class possessing XO inhibitory potential) was used as lead structure for further optimization. By means of structure‐based classical bioisosterism, quinolone was used as an isoster for chromone (a bicyclic unit present in flavones), owing to the bioactive potential and drug‐like properties of quinolones. This type of replacement does not alter the shape and structural features required for XO inhibition, and also provides some additional interaction sites, without the loss of hydrogen bonding and hydrophobic and arene–arene interactions. In the present study, a series of 2‐aryl/heteroaryl‐4‐quinolones (aza analogs of flavones) was rationally designed, synthesized and evaluated for in vitro XO inhibitory activity. Some notions about structure–activity relationships are presented indicating the influence of the nature of the 2‐aryl ring on the inhibitory activity. Important interactions of the most active compound 3l (IC50 = 6.24 µM) with the amino acid residues of the active site of XO were figured out by molecular modeling.

Silica supported Bronsted acids as catalyst in organic transformations： A comprehensive review

Abstract Bronsted acid catalysts have been used in a number of organic transformations. To overcome limitations, such as toxicity, volatility, high price and hazardous nature of the conventional methods, the catalysts are adsorbed on silica gel to give the benefits and advantages of ready availability, simple work-up procedure, long catalytic life, environment-friendliness, good to excellent yields and recyclability. The uses of such catalysts have gained importance worldwide. This article describes some of the important silicated catalysts, namely, heteropolyacids, polyphosphoric acid, perchloric acid, fluoroboric acid, and silicated sulphuric acid. These catalysts have been used in a number of organic reactions to yield compounds that are important in the chemical and pharmaceutical industries. We summarize the beneficial effects of these catalysts and the reports that have been published on them in the past several years. In the present review, the description of the catalysts are introduced followed by a recent research history, and a comparison between the silica supported catalysts and other (polymer) supported catalysts. The article ends up giving the advantages of these catalytic systems over the conventional catalyst.

Vasicine and structurally related quinazolines

Natural products are diverse sources of important chemical constituents. Most of the metabolites isolated from them are heterocycles possessing diverse pharmacological actions. Vasicine, a heterocyclic alkaloid possessing a privileged quinazoline nucleus is primarily present in the leaves o the plant Adhatoda vasica nees, family Acanthaceae. Vasicine and structurally related quinazolines have been an area of interest for the researchers all around the world. The present review provides an up to date compilation of the alkaloid vasicine, its biosynthesis, synthesis, biological attributes, design of its synthetic analogues along with structurally related quinazolines.

Synthesis and evaluation of naphthoflavones as a new class of non purine xanthine oxidase inhibitors

In view of reported xanthine oxidase inhibitory potential of naphthopyrans and flavones, naphthoflavones as hybrids of the two were designed, synthesized and evaluated for in vitro xanthine oxidase inhibitory activity in the present study. The results of the assay revealed that the naphthoflavones possess promising inhibitory potential against the enzyme with IC50 values ranging from 0.62 to 41.2 μM. Structure activity relationship indicated that the nature and placement of substituents on the phenyl ring at 2nd position remarkably influences the inhibitory activity. Substitution of halo and nitro groups at ortho and para position of the phenyl ring (2nd position) remarkably favored the activity. NF-4 with p-fluoro phenyl ring was the most potent inhibitor with IC50 value of 0.62 μM. Enzyme kinetics study was also performed to investigate the inhibition mechanism and it was found that the naphthoflavones displayed mixed type inhibition. The basis of significant inhibition of xanthine oxidase by NF-4 was rationalized by molecular modeling studies.

Microwave assisted synthesis of naphthopyrans catalysed by silica supported fluoroboric acid as a new class of non purine xanthine oxidase inhibitors.

A series of naphthopyrans was synthesized employing silica supported fluoroboric acid under solvent free conditions in a microwave reactor. The catalytic influence of HBF4-SiO2 was investigated in detail to optimize the reaction conditions. The synthesised compounds were evaluated for in vitro xanthine oxidase inhibitory activity for the first time. Structure-activity relationship analyses have also been presented. Among the synthesised compounds, NP-17, NP-19, NP-20, NP-23, NP-24, NP-25 and NP-26 were the active inhibitors with an IC50 ranging from 4 to 17 μM. Compound NP-19 with a thiophenyl ring at position 1 emerged as the most potent xanthine oxidase inhibitor (IC50=4 μM) in comparison to allopurinol (IC50=11.10 μM) and febuxostat (IC50=0.025 μM). The basis of significant inhibition of xanthine oxidase by NP-19 was rationalized by its molecular docking at MTE binding site of xanthine oxidase.

Tubulin inhibitors: a patent survey.

Tubulin is one of the most useful and strategic molecular targets for anticancer drugs. The dynamic process of microtubule assembly and disassembly can be blocked by various agents that bind to distinct sites in the β-tubulin subunit. By interfering with microtubule function in vitro, these agents arrest cells in mitosis, eventually leading to cell death, by both apoptosis and necrosis. So far, three binding domains have been identified a) the colchicine site close to the α/β interface, b) the area where the vinca alkaloids bind, and c) the taxane-binding pocket. This review compiles the patent literature up to 2013 and offers a detailed account of all the advances on Tubulin inhibitors (lead molecules) along with in depth knowledge about the number of novel scaffolds, modified analogs and derivatives of the lead molecules. Colchicine binding site remains the most explored site indicated by the patent survey as majority of the patents revolves around phenstatin and combretastatin based molecules where the key structural feature for tubulin inhibition is an appropriate arrangement of the two aromatic rings at an appropriate distance and optimal dihedral angle maximizing interactions with tubulin. A brief account of promising tubulin inhibitors in stages of clinical development and some strategies for the development of potent molecules overcoming the problem of drug resistance have also been discussed.

Design strategies, structure activity relationship and mechanistic insights for purines as kinase inhibitors.

Kinases control a diverse set of cellular processes comprising of reversible phosphorylation of proteins. Protein kinases play a pivotal role in human tumor cell proliferation, migration and survival of neoplasia. In the recent past, purine based molecules have emerged as significantly potent kinase inhibitors. In view of their promising potential for the inhibition of kinases, this review article focuses on purines which have progressed as kinase inhibitors during the last five years. A detailed account of the design strategies employed for the synthesis of purine analogs exerting inhibitory effects on diverse kinases has been presented. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the purine analogs for kinase inhibition. The interactions with the amino acid residues responsible for kinase inhibitory potential of purine based molecules have also been discussed. In this assemblage, purine based protein kinase inhibitors patented in the past have also been summarized in the tabular form. This compilation will be of great interest for the researchers working in the area of protein kinase inhibitors.

Anti-Cancer Pyrimidines in Diverse Scaffolds: A Review of Patent Literature

Pyrimidine ring is the building unit of DNA and RNA and thus pyrimidine based chemical architectures exhibit diverse pharmacological activities. Among the reported medicinal attributes of pyrimidines, anticancer activity is the most extensively reported. The anticancer potential of pyrimidines in fused scaffolds has also been evidenced through number of research article and patent literature. The pyrimidines based scaffolds have exerted their cell killing effects through varied mechanisms which indicate their potential to interact with diverse enzymes/ targets/receptors. This review article strictly focuses on the patent literature from 2009 onwards. The structure of the potent compounds, their IC50 values, models/assays used for the anticancer evaluation and the enzymes/ receptors/ targets involved have been presented in this compilation. Significant number of patents i.e. 59 have been published on pyrimidine based anticancer agents from 2009-2014 (from 2009 through the present date) which clearly indicate that this heterocycle is an area of focus at present for researchers all over the globe. Moreover, out of the 59 patents published during this period, 32 have been published from 2012 onwards which further highlights the present interest of the researcher towards pyrimidine based anticancer agents. The promising activity displayed by these pyrimidine based scaffolds clearly places them in forefront as potential future drug candidates. The present compilation can be extremely beneficial for the medicinal chemists working on design and synthesis of anticancer drugs.

Triazole linked mono carbonyl curcumin-isatin bifunctional hybrids as novel anti tubulin agents: Design, synthesis, biological evaluation and molecular modeling studies

Keeping in view the limitations associated with currently available anticancer drugs, molecular hybrids of mono carbonyl curcumin and isatin tethered by triazole ring have been synthesized and evaluated for in vitro cytotoxicity against THP-1, COLO-205, HCT-116, A549, HeLa, CAKI-I, PC-3, MiaPaca-2 human cancer cell lines. The results revealed that the compounds SA-1 to SA-9, SB-2, SB-3, SB-4, SB-7 and SC-2 showed a good range of IC50 values against THP-1, COLO-205, HCT-116 and PC-3 cell lines, while the other four cell lines among these were found to be almost resistant. Structure activity relationship revealed that the nature of Ring X and substitution at position R influences the activity. Methoxy substituted phenyl ring as Ring X and H as R were found to be the ideal structural features. The most potent compounds (SA-2, SA-3, SA-4, SA-7) were further tested for tubulin inhibition. Compound SA-2 was found to significantly inhibit the tubulin polymerization (IC50=1.2 μM against HCT-116). Compound SA-2, moreover, lead to the disruption of microtubules as confirmed by immunofluorescence technique. The significant cytotoxicity and tubulin inhibition by SA-2 was streamlined by molecular modeling studies where it was docked at the curcumin binding site of tubulin.