DNA Binding Ellipticine Analogues: Synthesis,Biological Evaluation,and Structure–Activity Relationships

Novel angular and branched ellipticine‐correlated anticancer agents were developed. In particular, compound 24 , with two basic side chains on opposite sides of the molecule, exhibits cytotoxicity in the nanomolar range, acting as a DNA intercalator and topoisomerase II inhibitor. SAR studies with pyridocarbazole derivatives in comparison with corresponding smaller pyrroloquinolines are discussed.

     

Design, synthesis, and biological evaluation of the first podophyllotoxin analogues as potential vascular-disrupting agents

We designed and synthesized two novel series of azapodophyllotoxin analogues as potential antivascular agents. A linker was inserted between the trimethoxyphenyl ring E and the tetracyclic ABCD moiety of the 4-aza-1,2-didehydropodophyllotoxins. In the first series, the linker enables free rotation between the two moieties; in the second series, conformational restriction of the E nucleus was considered. We have identified several new compounds with inhibitory activity toward tubulin polymerization similar to that of CA-4 and colchicine, while displaying low cytotoxic activity against normal and/or cancer cells. An aminologue and a methylenic analogue were shown to disrupt endothelial cell cords on Matrigel at subtoxic concentrations, and an original assay of drug washout allowed us to demonstrate the rapid reversibility of this effect. These two new analogues are promising leads for the development of vascular-disrupting agents in the podophyllotoxin series.     

Design, synthesis and biological evaluation of sugar-derived Ras inhibitors

The design and synthesis of novel Ras inhibitors with a bicyclic scaffold derived from the natural sugar D-arabinose are presented. Molecular modelling showed that these ligands can bind Ras by accommodating the aromatic moieties and the phenylhydroxylamino group in a cavity near the Switch II region of the protein. All the synthetic compounds were active in inhibiting nucleotide exchange on p21 human Ras in vitro, and two of them selectively inhibited Ras-dependent cell growth in vivo.     

Synthesis, modeling, and biological evaluation of analogues of the semisynthetic brevetoxin antagonist beta-naphthoyl-brevetoxin

Brevetoxins are neurotoxic compounds produced by the dinoflagellate Karenia brevis. Extensive blooms induce neurotoxic shellfish poisoning (NSP) and asthma-like symptoms in humans. beta-naphthoyl-brevetoxin, the first semisynthetic brevetoxin antagonist, has been defined as the lead compound in the investigation of the mechanisms of bronchoconstriction induced by inhaled brevetoxins and relaxation or reversal of those effects by selected derivatives. In pursuit of more potent and effective brevetoxin antagonists, a series of beta-naphthoyl-brevetoxin analogues have been synthesized. Activities were determined by competitive displacement of tritiated brevetoxin-3 from rat brain synaptosomes and by lung resistance measurements in sheep. Additionally, preliminary computational structural studies have been performed. All analogues bound to rat brain synaptosomes with affinities similar to beta-naphthoyl-brevetoxin but exhibited very different responses in sheep. The biological evaluations along with computational studies suggest that the brevetoxin binding site in rat brain synaptosome might be different from the ones in lung tissue and both steric and electrostatic factors contribute to the efficacy of brevetoxin antagonism.     

Design and synthesis of cyclopeptide analogues of the potent histone deacetylase inhibitor FR235222

Various structurally modified analogues of FR235222 (1), a natural tetrapeptide inhibitor of mammalian histone deacetylases, were prepared in a convergent approach. The design of the compounds was aimed to investigate the effect of structural modifications of the tetrapeptide core involved in enzyme binding in order to overcome some synthetic difficulties connected with the natural product 1. The modifications introduced could also help identify key structural features involved in the mechanism of action of these compounds. The prepared molecules were subjected to in vitro pharmacological tests, and their potency was tested on cultured cells. Two of the components of the array were found to be more potent than the parent compound 1 and almost as efficient as trichostatin A (TSA). These results demonstrate that it is possible to synthesize highly active cyclic tetrapeptides using commercially available amino acids (with the exception of 2-amino-8-oxodecanoic acid, Ahoda). The nature of the residue in the second position of the cyclic peptide and the stereochemistry of the Ahoda tail are important for the inhibitory activity of this class of cyclic tetrapeptide analogues.     

Design, synthesis, biological evaluation, and molecular modeling studies of TIBO-like cyclic sulfones as non-nucleoside HIV-1 reverse transcriptase inhibitors

TIBO- and TBO-like sulfone derivatives 1 and 2 were designed, synthesized, and tested for their ability to block the replication cycle of HIV-1 in infected cells. The anti-HIV-1 activities of sulfones 3, which were intermediates in the syntheses of 1 and 2, were also evaluated. Surprisingly, the sulfone analogues of TIBO R82913 (compounds 1) were inactive, whereas interesting results were obtained for truncated derivatives 2. Compound 2 w was the most potent among this series in cell-based assays (EC50=0.07 microM, CC50>200 microM, SI>2857). It was twofold less potent than R82913, but more selective. An X-ray crystallographic analysis was carried out to establish the absolute configuration of 2 w and its enantiomer 2 x, which were obtained by semipreparative HPLC of 2 v, one of the most potent racemates. Compounds 1-3 were proven to target HIV-1 RT. In fact, representative derivatives inhibited recombinant HIV-1 RT in vitro at concentrations similar to those active in cell-based assays. 3D QSAR studies and docking simulations were developed on TIBO- and TBO-like sulfone derivatives to rationalize their anti-HIV-1 potencies and to predict the activity of novel untested sulfone derivatives. Predictive 3D QSAR models were obtained with a receptor-based alignment by docking of TIBO- and TBO-like derivatives into the NNBS of RT.     

Synthesis and biological evaluation of N-acylhydrazones as inhibitors of MurC and MurD ligases

The Mur ligases have an essential role in the intracellular biosynthesis of bacterial peptidoglycan, and they represent attractive targets for the design of novel antibacterials. A series of compounds with an N-acylhydrazone scaffold were synthesized and screened for inhibition of the MurC and MurD enzymes from Escherichia coli. Compounds with micromolar inhibitory activities against both MurC and MurD were identified, and some of them also showed antibacterial activity.     

Synthesis and biological evaluation of boronic acid containing cis-stilbenes as apoptotic tubulin polymerization inhibitors

A series of boronic acid containing cis-stilbenes as potent inhibitors of tubulin polymerization was synthesized by the introduction of boronic acid as an acceptor-type functional group into the aromatic ring B of the combretastatin framework. High cell-growth inhibition was observed with boron compounds 13 c and 13 d, in which a hydroxy group on the aromatic ring B of combretastatin A-4 was replaced with boronic acid; IC50 values toward B-16 and 1-87 cell lines are 0.48-2.1 microM. Compounds 13 c and 13 d exhibited significant inhibitory activity toward tubulin polymerization (IC50=21-22 microM). The carboxylic acid derivative 17, which can be considered as a mimic of boronic acid 13 c, did not show significant inhibition of cell growth or tubulin polymerization. According to the FACScan analysis using Jurkat cells, apoptosis was induced after incubation for 8 h with 13 c at a concentration of >10(-8) M. Growth inhibitory experiments against a panel of 39 human cancer cell lines revealed 13 c to inhibit growth differently than combretastatin A-4; the correlation coefficient (r) between the two compounds was 0.553 in the COMPARE analysis.     

Asymmetric Synthesis and Biological Evaluation of Glycosidic Prodrugs for a Selective Cancer Therapy

A severe limitation in cancer therapy is the often insufficient differentiation between malign and benign tissue using known chemotherapeutics. One approach to decrease side effects is antibody‐directed enzyme prodrug therapy (ADEPT). We have developed new glycosidic prodrugs such as (?)‐(1S)‐ 26 b based on the antibiotic (+)‐duocarmycin SA ((+)‐ 1 ) with a QIC₅₀ value of 3500 (QIC₅₀=IC₅₀ of prodrug/IC₅₀ of prodrug+enzyme) and an IC₅₀ value for the corresponding drug (prodrug+enzyme) of 16 pM . The asymmetric synthesis of the precursor (?)‐(1S)‐ 19 was performed by arylation of the enantiomerically pure epoxide (+)‐(S)‐ 29 (≥98 % ee).     

Inhibition of Golgi mannosidase II with mannostatin A analogues: synthesis, biological evaluation, and structure-activity relationship studies

Mannostatin and aminocyclopentitetrol analogues with various substitutions at the amino function were synthesized. These compounds were tested as inhibitors of human Golgi and lysosomal alpha-mannosidases. Modification of the amine of mannostatin had only marginal effects, whereas similar modifications of aminocyclopentitetrol led to significantly improved inhibitors. Ab initio calculations and molecular docking studies were employed to rationalize the results. It was found that mannostatin and aminocyclopentitretrol could bind to Golgi alpha-mannosidase II in a similar mode to that of the known inhibitor swainsonine. However, due to the flexibility of the five-membered rings of these compounds, additional low-energy binding modes could be adopted. These binding modes may be relevant for the improved activities of the benzyl-substituted compounds. The thiomethyl moiety of mannostatin was predicted to make favorable hydrophobic interactions with Arg228 and Tyr727 that would possibly account for its greater inhibitory activity.     

Design,Synthesis, and in vitro Biological Evaluation of 3,5‐Dimethylisoxazole Derivatives as BRD4 Inhibitors

BRD4 has been identified as a potential target for blocking proliferation in a variety of cancer cell lines. In this study, 3,5‐dimethylisoxazole derivatives were designed and synthesized with excellent stability in liver microsomes as potent BRD4 inhibitors, and were evaluated for their BRD4 inhibitory activities in vitro. Gratifyingly, compound 11 h [3‐((1‐(2,4‐difluorophenyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)‐6‐(3,5‐dimethylisoxazol‐4‐yl)‐4‐phenyl‐3,4‐dihydroquinazolin‐2(1H)‐one] exhibited robust potency for BRD4(1) and BRD4(2) inhibition with IC₅₀ values of 27.0 and 180 nm , respectively. Docking studies were performed to illustrate the strategy of modification and analyze the conformation in detail. Furthermore, compound 11 h was found to potently inhibit cell proliferation in the BRD4‐sensitive cell lines HL‐60 and MV4‐11, with IC₅₀ values of 0.120 and 0.09 μm , respectively. Compound 11 h was further demonstrated to downregulate c‐Myc levels in HL‐60 cells. In summary, these results suggest that compound 11 h is most likely a potential BRD4 inhibitor and is a lead compound for further investigations.     

Design,Synthesis, and Biological Evaluation of Pyrazoline‐Based Hydroxamic Acid Derivatives as Aminopeptidase N (APN) Inhibitors

Aminopeptidase N (APN) has been recognized as a target for anticancer treatment due to its overexpression on diverse malignant tumor cells and association with cancer invasion, metastasis and angiogenesis. Herein we describe the synthesis, biological evaluation, and structure–activity relationship study of two new series of pyrazoline analogues as APN inhibitors. Among these compounds, 5‐(2‐(2‐(hydroxyamino)‐2‐oxoethoxy)phenyl)‐3‐phenyl‐4,5‐dihydro‐1H‐pyrazole‐1‐carboxamide (compound 13 e ) showed the best APN inhibition with an IC₅₀ value of 0.16±0.02 μm , which is more than one order of magnitude lower than that of bestatin (IC₅₀=9.4±0.5 μm ). Moreover, compound 13 e was found to inhibit the proliferation of diverse carcinoma cells and to show potent anti‐angiogenesis activity. At the same concentration, compound 13 e presents significantly higher anti‐angiogenesis activity than bestatin in human umbilical vein endothelial cells (HUVECs) capillary tube formation assays. The putative binding mode of 13 e in the active site of APN is also discussed.