Letters in Drug Design & Discovery - Volume 8, Issue 6, 2011

We report the synthesis and evaluation of a novel PPARδ agonist, compound 12a, characterized by a benzisoxazole ring. Compound 12a exhibited a potent human PPARδ transactivation activity (EC50: 0.011 μM). Preliminary biological testing suggests that compound 12a has significant HDL-cholesterol elevating effect in an animal model of dyslipidemia.

In order to investigate the SAR of Ezetimibe analogs for cholesterol absorption inhibitions, amide group and electron-deficient pyridine ring were introduced to the C-(3) carbon chain of Ezetimibe. Eight new derivatives of the 2- azetidinone cholesterol absorption inhibitors have been synthesized, and all of them were enantiomerically pure. All the new compounds were evaluated for their activity to inhibit cholesterol absorption in hamsters, and most of them showed comparable effects in lowering the levels of total cholesterol in the serum.

Quantitative structure activity relationship approach using enhanced replacement method for variable selection was applied to a series of imidazole containing tetrahydrobenzodiazepines as inhibitors of farnesyltransferase. For the purpose the dataset was divided into training set of 31 compounds and test set of 5 compounds using k means clustering. Statistically significant equations were obtained with high correlation coefficient coefficient (R=0.9637) and low standard deviation (S=0.3715). The robustness of the model was confirmed with the help of R2cv with a value of 0.8886, Y scrambling and by predicting the activities of test compounds. A good correlation of KierA3 shape indices and polarizability with the farnesyltransferase inhibitory activity was achieved.

We report the results of the evaluation of a series of imidazole-based compounds against the enzyme 17α- hydroxylase/17,20-lyase (P-45017α). The results show that the compounds were, in general, weak inhibitors of P-45017α in comparison to the standard inhibitor ketoconazole (KTZ) - one was, however, found to be more potent than KTZ.

In order to explore structure-activity relationship (SAR) associated with xanthone framework, a series of prenylated xanthone derivatives 2-9 was synthesized from the key building block 1,3,6,8-tetrahydroxyxanthone 1 and evaluated for their in vitro growth inhibitory activities against HeLa and MDA-MB-231 human cancer cell lines. The in vitro evidence indicated that the inhibitory activity was significantly influenced by the position and number of linked group on the xanthone skeleton, and the presence of chroman-4-one moiety in the xanthone scaffold was found to be critically important for strong cytotoxic activity. The novel 2H-xanthene-3,9-dione analogues 3 and 4 were reported to elicit potent activities comparable to those of standard drugs doxorubicin and cisplatin. This preliminary investigation has highlighted the therapeutic potential of 2H-xanthene-3,9-dione derivatives to be exploitable as lead compound for the development of potent HeLa and MDA-MB-231 cancer cell inhibitors.

Vasopressin receptor antagonists (vaptans) are a new class of drugs to treat congestive heart failure. Since there are three subtypes of the receptor located in different tissues, it is important to devise tailor-made vaptans to target the appropriate receptor subtype. The binding of three vaptans, OPC21268, mozavaptan and tolvapatan was measured to the human V1-vascular vasopressin receptor (hV1R). Whereas arginine vasopressin (AVP) binds to hV1R and hV2R with equal affinity, vaptans interact differently with the receptor subtypes. The interaction of the three vaptans to the hV1R was probed by binding experiments to point mutants of residues postulated to line the binding pocket. The measurements suggest that the binding pocket on the hV1R is too small for tight binding of tolvaptan. The somewhat smaller mozavaptan is a slightly better binder to the hV1R. The data suggest ways to increase the affinity of tolvaptan to the hV1R by chemical modification.

Zerumbonoquinone 10 and zerumbonaminone 11 have been designed to release toxic moieties selectively and preferentially under reductive conditions. These compounds were synthesized by coupling the quinone delivery system with zerumbone alcohol 8 and amine 9. All compounds were evaluated for cytotoxicity against KB (non reductase overexpressing cells), NCI-H187 and MCF-7 (reductase overexpressing cells) and normal cells (Vero cells). Bioreductive compounds 10 and 11 were found to act as bioreductive anticancer agents exhibiting less cytotoxicity than the parents 8 and 9 in KB cells with good stability, and were partially bioreductively active against MCF-7 and NCI-H187 cells.

2,4-Disubstituted pyrroles were polycondensed and tested for lipid-lowering effects in mice. Fluoro-substituted pyrrole monomers and polymers lowered total serum cholesterol by 30-35% and LDL-cholesterol by 47-64%. The lipidlowering effects were similar for polymers and their monomers, however, the polymers produced these effects at dosage concentrations 1/8th that of the monomers.

Novel NO-donor-caffeic acid hybrids with antioxidant, nitric oxide release and vasodilator properties were designed and synthesized through a symbiotic approach using caffeic acid and three different NO-donating groups such as nitric ester, 4-hydroxyl-3-phenylfuroxan and 4-hydroxymethyl-3-phenylsulfonylfuroxan. The antioxidant activities of these hybrid products were assessed by DPPH assay and by detecting the TBARS produced in the ferrous salt/ascorbate induced autoxidation of lipids which were present in microsomial membranes of rat hepatocytes. The nitric oxide release activities were assessed by indirect evaluation of the produced nitrite. The vasodilator activities were determined through an in vitro vascular relaxation assay (organ bath) using PGF2α-precontracted porcine pulmonary arteries. The results showed that the target phenylsulfonylfuroxan 12, especially 12a while keeping the antioxidant activity, showed more NO release activity and vasodilating activity than isosorbide dinitrate (ISDN). Thus 12a may be considered as a novel potent anti-atherosclerosis's drug candidate.

Seven novel 6-(1-acetyl-3-(6-substituted-2-oxo-2H-chromen-3-yl)-4,5-dihydro-1H-pyrazol-5-yl)-2-amino-4- substituted-4H-chromene-3-carbonitrile derivatives were synthesized and characterized by 1H NMR and 13C NMR. All of the compounds have been screened for their antibacterial activity. The results show that compounds 4d and 4g displayed significant activity with MIC of 1.562 μg/mL against B. subtilis ATCC 6633 and 1.562, 3.125 μg/mL against S. aureus ATCC 6538.

The synthesis, in vitro evaluation and conformational study of small-size peptides acting as antifungal agents are reported. These peptides displayed antifungal activity against human pathogenic strains including Candida albicans and Cryptococcus neoformans. Among the peptides reported here, RQWRRWWQR-NH2 exhibited the strongest activity against Cryptococcus neoformans. Our results allowed us to reduce in size these bioactive peptides from 16 to 11 and to 9 amino acid residues in total. Despite their reduction, they still maintained and even enhanced the antifungal activity detected for penetratin. A conformational and electronic structure analysis on these peptides was also performed by using molecular mechanics calculations in conjunction with Molecular Electrostatic Potentials (MEP) maps.

Acid-ester and acid-amide norcantharidin derivatives are prepared using a ‘one-pot’ synthetic procedure utilizing the ThalesNano H-cube™ flow hydrogenator. Traditionally, rapid library generation and reaction scale up of these analogues was limited by the batch wise hydrogenation of 5,6-dehydronorcantharidin. This was resolved with the use of flow chemistry. With no associated scale up issues, a method was devised to produce norcantharidin, along with acid-ester and acid-amide analogues on any scale necessary for biological screening.

A series of 19 isonicotinic acid hydrazide derivatives has been synthesized and evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv using alamar blue susceptibility test. The synthesized compounds inhibit Mycobacterium tuberculosis H37Rv strain with minimum inhibitory concentration ranging from (0.00014-0.01174 mM). Among all synthesized compounds seven derivatives 2a, 2b, 2e, 2h, 2l, 2m and 2q were more potent than isoniazid and the compound 2q emerged as the most potent derivative, being more effective than isoniazid with an (MIC 0.00023 mM) in vitro. The results demonstrated the potential and importance of developing new isoniazid derivatives against Mycobacterium infections.