6-Aryl substituted 4-(4-cyanomethyl) phenylamino quinazolines as a new class of isoform-selective PI3K-alpha inhibitors.

Isoform-selective inhibition of PI3K-α has been identified as one of the important strategy to discover effective and safer anticancer agents. Herein, we report discovery of 'quinazoline' as a new chemotype for isoform-selective PI3K-α inhibitors. The indolyl substituted quinazoline 9u displayed selective inhibition of PI3K-α with IC50 value of 0.201 µM with >49.7 over PI3K-ß, and δ-isoforms. Quinazoline 9u also inhibited PI3K-γ with IC50 value of 0.750 µM (3.7 fold selective for α-versus γ-isoform). The isoform-selective inhibition was also demonstrated at protein-expression level by western-blot analysis in MCF-7 and PC-3 cells. The isoform-selective inhibitor 9u also showed inhibition of phospho-Akt levels in these cells. Quinazoline 9u showed in-vitro cytotoxicity in MCF-7 cells with GI50 of 7 µM, which was highly selective for cancer cells, as it was non-toxic to normal cells fR2, HEK293 and hGF (GI50 > 50 µM). Compound 9u at 25 mg/kg dose showed 62 and 37% TGI in Ehrlich Ascites Carcinoma and Ehrlich Solid Tumor mice models. In nutshell, our efforts to identify potent and efficacious PI3K inhibitors resulted in the discovery of a new class of isoform-selective PI3K-α inhibitors possessing promising in-vivo anticancer activity.

Meridianin derivatives as potent Dyrk1A inhibitors and neuroprotective agents.

Meridianins are a group of marine-derived indole alkaloids which are reported to possess kinase inhibitory activities. In the present Letter, we report synthesis of N1-substituted and C-ring modified meridianin derivatives and their evaluation as Dyrk1A inhibitors and neuroprotective agents. Among the library of 52 compounds screened, morpholinoyl linked derivative 26b and 2-nitro-4-trifluoromethyl phenyl sulfonyl derivative 29v displayed potent inhibition of Dyrk1A with IC50 values of 0.5 and 0.53 µM, respectively. The derivative 26b also inhibited Dyrk2 and Dyrk3 with IC50 values of 1.4 and 2.2 µM, respectively showing 2.2 and 4.4 fold selectivity for Dyrk1A with respect to Dyrk2 and Dyrk3. The compound 26b was not cytotoxic to human neuroblastoma SH-SY5Y cells (IC50>100 µM) and it displayed significant neuroprotection against glutamate-induced neurotoxicity in these cells at 10 µM. Molecular modelling studies of compound 26b led to identification of key interactions in the binding site of Dyrk1A and the possible reasons for observed Dyrk1A selectivity over Dyrk2.

Synthesis, antimalarial and antitubercular activities of meridianin derivatives.

Meridianins are marine-derived indole alkaloids, known to possess kinase inhibitory and antimalarial activities. A series of N-aryl and heteroaryl sulfonamide derivatives of meridianins were prepared and screened for antimalarial activity against D6 and W2 strains of Plasmodium falciparum. 2-Nitro-4-trifluoromethyl sulfonamide derivative 14v displayed promising antiplasmodial activity against both strains with IC50 values of 2.56 and 3.41 µM, respectively. These compounds were not cytotoxic to mammalian cell lines including VERO (monkey kidney fibroblasts), LLC-PK1 (pig kidney epithelial cells) and four cancer cell lines; SK-MEL (human malignant, melanoma), KB (human epidermal carcinoma), BT-549 (ductal carcinoma), SK-OV-3 (human ovary carcinoma) up to 25 µg/ml. Furthermore, all sulfonamide derivatives along with acyl, alkyl and C-ring modified derivatives of meridianins were screened for antitubercular activity against a sensitive strain (H37Rv) of Mycobacterium tuberculosis (Mtb), wherein several compounds showed MIC values in the range of 5.2-304.8 µM. Meridianin C (3) and meridianin G (7) showed anti-tubercular activity with MIC values of 111.1 and 304.8 µM, respectively. The C-ring modified analog 12 exhibited potent anti-tubercular activity against H37Rv strain of Mtb with MIC of 5.2 µM. Furthermore, the most potent analogs 11b and 12 were screened against two clinical isolates of M. tuberculosis INH(R) and MDR and one laboratory generated mutant strain Rif(R). These two analogs 11b and 12 displayed promising activity against these resistant strains with MIC values in the range of 5.2-187.7 µM. This is the first report on the anti-tubercular activity of this scaffold.

Discovery of 3,3'-diindolylmethanes as potent antileishmanial agents.

An efficient protocol for synthesis of 3,3'-diindolylmethanes using recyclable Fe-pillared interlayered clay (Fe-PILC) catalyst under aqueous medium has been developed. All synthesized 3,3'-diindolylmethanes showed promising antileishmanial activity against Leishmania donovani promastigotes as well as axenic amastigotes. Structure-activity relationship analysis revealed that nitroaryl substituted diindolylmethanes showed potent antileishmanial activity. The 4-nitrophenyl linked 3,3'-diindolylmethane 8g was found to be the most potent antileishmanial analog showing IC50 values of 7.88 and 8.37 µM against both L. donovani promastigotes and amastigotes, respectively. Further, a pharmacophore based QSAR model was established to understand the crucial molecular features of 3,3'-diindolylmethanes essential for potent antileishmanial activity. These compounds also exhibited promising antifungal activity against Cryptococcus neoformans, wherein fluorophenyl substituted 3,3'-diindolylmethanes were found to be most potent antifungal agents. Developed synthetic protocol will be useful for economical and eco-friendly synthesis of potent antileishmanial and antifungal 3,3'-diindolylmethane class of compounds.

QSAR and pharmacophore study of Dyrk1A inhibitory meridianin analogs as potential agents for treatment of neurodegenerative diseases.

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1A) is a protein kinase with diverse functions in neuronal development and adult brain physiology. Elevated levels of Dyrk1A are associated with the pathology of neurodegenerative diseases and have been implicated in some neurobiological alterations of Down syndrome, such as mental retardation. Meridianins are marine derived indole alkaloids exhibiting anti-proliferative activity as well as are known to inhibit panel of kinases. In the present article, a descriptor based QSAR study was carried out for a series of meridianin analogs inhibiting Dyrk1A to find out structural features which are crucial for biological activity. Developed QSAR model showed good correlation coefficient (r > 0.9), higher F value (F > 20) and excellent predictive power (r2 cv and r2 pred > 0.6). Activity of naturally occurring meridianins was also predicted using developed model. The study indicated that kier Chi4 path/cluster, total lipole, VAMP polarization ZZ component, dipole moment Z component and log P plays important role in Dyrk1A inhibition. Further analysis of pharmacophore model using PHASE module of Schrodinger revealed that two hydrogen bond acceptors (A), two hydrogen bond donors (D) and two hydrophobic aromatic rings (R) are crucial molecular features that predict binding affinity for meridianins to the Dyrk1A enzyme. These observations provide important insights to the key structural requirements of meridianins for potent Dyrk1A inhibition. Excellent statistical results of developed models strongly suggest that these models are reasonable for prediction of the activity of new inhibitors and in future drug design.

Tandem one-pot synthesis of flavans by recyclable silica-HClO4 catalyzed Knoevenagel condensation and [4 + 2]-Diels-Alder cycloaddition.

An efficient one-pot multi-component synthesis of flavans using perchloric acid supported on silica as a recyclable heterogeneous catalyst has been described. This is the first report of direct one-step construction of a flavan skeleton from a phenolic precursor. The method involves a Knoevenagel-type condensation leading to in situ formation of transient O-quinone methide which further undergoes [4 + 2]-Diels-Alder cycloaddition with styrene to yield a flavan skeleton. The method provides easy access to a wide range of bio-active natural products viz. flavonoids, anthocyanins and catechins.