Reactions of solid-supported reagents and solid supports with alcohols and phenols through their hydroxyl functional group

Design, Synthesis and Evaluation of Novel 3/4-((Substituted benzamidophenoxy) methyl)-N-hydroxybenzamides/propenamides as Histone Deacetylase Inhibitors and Antitumor Agents

BACKGROUND

Histone Deacetylase (HDAC) inhibitors represent an extensive class of targeted anticancer agents. Among the most explored structure moieties, hydroxybenzamides and hydroxypropenamides have been demonstrated to have potential HDAC inhibitory effects. Several compounds of these structural classes have been approved for clinical uses to treat different types of cancer, such as givinostat (ITF2357) and belinostat (PXD-101).

AIMS

This study aims at developing novel HDAC inhibitors bearing N-hydroxybenzamides and Nhydroxypropenamides scaffolds with potential cytotoxicity against different cancer cell lines.

METHODS

Two new series of N-hydroxybenzamides and N-hydroxypropenamides analogues (4a-j, 6a-j) designed based on the structural features of nexturastat A, AR-42, and PXD-101, were synthesized and evaluated for HDAC inhibitory potency as well as cytotoxicity against three human cancer cell lines (SW620 (colorectal adenocarcinoma), PC3 (prostate adenocarcinoma), and NCI-H23 (adenocarcinoma, non-small cell lung cancer). Molecular simulations were finally carried out to gain more insight into the structure-activity relationships.

RESULTS

It was found that the N-hydroxypropenamides (6a-e) displayed very good HDAC inhibitory potency and cytotoxicity. Various compounds, e.g. 6a-e, especially compound 6e, were up to 5-fold more potent than suberanilohydroxamic acid (SAHA) in terms of cytotoxicity. These compounds also comparably inhibited HDACs with IC50 values in the sub-micromolar range. Docking experiments showed that these compounds bound to HDAC2 at the enzyme active binding site with the same binding mode of SAHA, but with higher binding affinities.

CONCLUSIONS

The two series of N-hydroxybenzamides and N-hydroxypropenamides designed and synthesized were potential HDAC inhibitors and antitumor agents. Further development of these compounds should be warranted.

Make room for iodine: systematic pore tuning of multivariate metal–organic frameworks for the catalytic oxidation of hydroquinones using hypervalent iodine

A multivariate approach has been to to establish the right balance between iodine loading and pore size for catalytic oxidative dearomatizations in MIL-53 (Al) and UiO-66 (Zr) MOFs.

Subtle Mitsunobu couplings under super-heating: the role of high-throughput continuous flow and microwave strategies

Fragile Mitsunobu reaction can efficiently be performed under super-heating.

Intramolecular monomer-on-monomer (MoM) Mitsunobu cyclization for the synthesis of benzofused thiadiazepine-dioxides

The utilization of a monomer-on-monomer (MoM) intramolecular Mitsunobu cyclization reaction employing norbornenyl-tagged (Nb-tagged) reagents is reported for the synthesis of benzofused thiadiazepine-dioxides. Facile purification was achieved via ring-opening metathesis (ROM) polymerization initiated by one of three metathesis catalyst methods: (i) free metathesis catalyst, (ii) surface-initiated catalyst-armed silica, or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles.

Small-Molecule Library Synthesis on Silicon-Functionalized SynPhase Lanterns

Silicon-functionalized SynPhase Lanterns are useful for the combinatorial synthesis of small-molecule libraries. Lanterns bearing an alkyl tethered diisopropylarylsilane are first activated with triflic acid to afford the corresponding diisopropylsilyl triflate, which is then reacted with a library scaffold bearing a free alcohol. Once the scaffold has been loaded onto the solid phase, a variety of transformations can be run, including amine cappings, cross-coupling reactions and amide bond formation. These reactions can yield a variety of products when run sequentially using split-pool synthesis strategies. Upon completion of the solid-phase transformations, the small-molecules are released from the Lanterns using HF/pyridine. Using the techniques described within, libraries can be made ranging from a few compounds to >10,000 members in a highly efficient manner.

Solid-phase, multicomponent reactions of methyleneaziridines: synthesis of 1,3-disubstituted propanones

[reaction: see text] Polymer-supported methyleneaziridines undergo ring opening by Grignard reagents under copper catalysis to yield metalloenamines which are alkylated in situ to yield ketimines. Filtration and washing of these Merrifield resin-bound intermediates prior to hydrolysis provides the corresponding 1,3-disubstituted propanones in a high state of purity without recourse to column chromatography.

Synthesis of 3-(Aryl)alkenyl-β-lactams by an Efficient Application of Olefin Cross-Metathesis on Solid Support

[reaction: see text] An efficient cross-metathesis on solid support for the synthesis of beta-lactam analogues of cholesterol absorption inhibitors is described. The applied strategy allows the introduction of diversity in positions 3 and 4 of the beta-lactam ring with excellent 3,4-trans selectivity and complete E selectivity at the C-3 side chain.

Focused Libraries of 16-Substituted Estrone Derivatives and Modified E-Ring Steroids: Inhibitors of 17ß-Hydroxysteroid Dehydrogenase Type 1

17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1), an oxidoreductase which has a preferential reductive activity using NADPH as cofactor, converts estrone to estradiol and is expressed in many steroidogenic tissues including breast and in malignant breast cells. As estradiol stimulates the growth and development of hormone-dependent breast cancer, inhibition of the final step of its synthesis is an attractive target for the treatment of this disease. The parallel synthesis of novel focused libraries of 16-substituted estrone derivatives and modified E-ring pyrazole steroids as new potent 17beta-HSD1 inhibitors is described. Substituted 3-O-sulfamoylated estrone derivatives were used as templates and were immobilised on 2-chlorotrityl chloride resin to give resin-bound scaffolds with a multi-detachable linker. Novel focused libraries of 16-substituted estrone derivatives and new modified E-ring steroids were assembled from these immobilised templates using solid-phase organic synthesis and solution-phase methodologies. Among the derivatives synthesised, the most potent 17beta-HSD1 inhibitors were 25 and 26 with IC50 values in T-47D human breast cancer cells of 27 and 165 nm, respectively. Parallel synthesis resulting in a library of C5'-linked amides from the pyrazole E-ring led to the identification of 62 with an IC50 value of 700 nM. These potent inhibitors of 17beta-HSD1 have a 2-ethyl substituent which will decrease their estrogenic potential. Several novel 17beta-HSD1 inhibitors emerged from these libraries and these provide direction for further template exploration in this area. A new efficient diastereoselective synthesis of 25 has also been developed to facilitate supply for in vivo evaluation, and an X-ray crystal structure of this inhibitor is presented.

The design of a potent inhibitor of the hepatitis C virus NS3 protease:BILN 2061?From the NMR tube to the clinic

The virally encoded serine protease NS3/NS4A is essential to the life cycle of the hepatitis C virus (HCV), an important human pathogen causing chronic hepatitis, cirrhosis of the liver, and hepatocellular carcinoma. Until very recently, the design of inhibitors for the HCV NS3 protease was limited to large peptidomimetic compounds with poor pharmacokinetic properties, making drug discovery an extremely challenging endeavor. In our quest for the discovery of a small-molecule lead that could block replication of the hepatitis C virus by binding to the HCV NS3 protease, the critical protein-polypeptide interactions between the virally encoded NS3 serine protease and its polyprotein substrate were investigated. Lead optimization of a substrate-based hexapeptide, guided by structural data, led to the understanding of the molecular dynamics and electronic effects that modulate the affinity of peptidomimetic ligands for the active site of this enzyme. Macrocyclic beta-strand scaffolds were designed that allowed the discovery of potent, highly selective, and orally bioavailable compounds. These molecules were the first HCV NS3 protease inhibitors reported that inhibit replication of HCV subgenomic RNA in a cell-based replicon assay at low nanomolar concentrations. Optimization of their biopharmaceutical properties led to the discovery of the clinical candidate BILN 2061. Oral administration of BILN 2061 to patients infected with the hepatitis C genotype 1 virus resulted in an impressive reduction of viral RNA levels, establishing proof-of-concept for HCV NS3 protease inhibitors as therapeutic agents in humans.