Identification of (1H)-pyrroles as histone deacetylase inhibitors with antitumoral activity

Synthesis of Pyrrole-2-Carboxylic Acid from Cellulose- and Chitin-Based Feedstocks Discovered by the Automated Route Search

The shift towards sustainable feedstocks for platform chemicals requires new routes to access functional molecules that contain heteroatoms, but there are limited bio-derived feedstocks that lead to heteroatoms in platform chemicals. Combining renewable molecules of different origins could be a solution to optimize the use of atoms from renewable sources. However, the lack of retrosynthetic tools makes it challenging to examine the extensive reaction networks of various platform molecules focusing on multiple bio-based feedstocks. In this study, a protocol was developed to identify potential transformation pathways that allow for the use of feedstocks from different origins. By analyzing existing knowledge on chemical reactions in large databases, several promising synthetic routes were shortlisted, with the reaction of D-glucosamine and pyruvic acid being the most interesting to make pyrrole-2-carboxylic acid (PCA). The optimized synthetic conditions resulted in 50 % yield of PCA, with insights gained from temperature variant NMR studies. The use of substrates obtained from two different bio-feedstock bases, namely cellulose and chitin, allowed for the establishment of a PCA-based chemical space.

Synthetic Conjugates of Ursodeoxycholic Acid Inhibit Cystogenesis in Experimental Models of Polycystic Liver Disease

BACKGROUND AND AIMS

Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of symptomatic biliary cysts. Current surgical and pharmacological approaches are ineffective, and liver transplantation represents the only curative option. Ursodeoxycholic acid (UDCA) and histone deacetylase 6 inhibitors (HDAC6is) have arisen as promising therapeutic strategies, but with partial benefits.

APPROACH AND RESULTS

Here, we tested an approach based on the design, synthesis, and validation of a family of UDCA synthetic conjugates with selective HDAC6i capacity (UDCA-HDAC6i). Four UDCA-HDAC6i conjugates presented selective HDAC6i activity, UDCA-HDAC6i #1 being the most promising candidate. UDCA orientation within the UDCA-HDAC6i structure was determinant for HDAC6i activity and selectivity. Treatment of polycystic rats with UDCA-HDAC6i #1 reduced their hepatomegaly and cystogenesis, increased UDCA concentration, and inhibited HDAC6 activity in liver. In cystic cholangiocytes UDCA-HDAC6i #1 restored primary cilium length and exhibited potent antiproliferative activity. UDCA-HDAC6i #1 was actively transported into cells through BA and organic cation transporters.

CONCLUSIONS

These UDCA-HDAC6i conjugates open a therapeutic avenue for PLDs.

Synthesis of 2-Benzylidene-3-Pyrrolines and Their Synthetic Transformation

A series of benzylidene-3-pyrrolines were prepared from chalcone derivatives, arylacetylene and sulfonamide via a three-step sequence without the isolation of intermediates. Typically, the reaction of 1,3-di-p-tolylprop-2-en-1-one with lithium phenylacetylide was followed by substitution with tosylamide and then silver-catalyzed 5-exo-dig cyclization to give N-tosyl-2-benzylidene-3,5-di-p-tolyl-2,5-dihydro-1H-pyrrole with a 86% yield. Furthermore, transformation to the corresponding substituted 3-pyrrolin-2-one and pyrrole by m-chloroperbenzoic acid (mcpba)-oxidation and acid-catalyzed aromatization, respectively, was investigated.

Copper-catalyzed carbene insertion and ester migration for the synthesis of polysubstituted pyrroles

A mild synthetic protocol to access 2-ester pyrroles through Cu(OTf)₂-catalysed carbene insertion/ester migration/cyclization of enaminones and α-diazo compounds is reported.

Application of 1,3-Dipolar Reactions between Azomethine Ylides and Alkenes to the Synthesis of Catalysts and Biologically Active Compounds

The (3+2) cycloaddition between azomethine ylides and alkenes is an efficient, convergent and stereocontrolled method for the synthesis of unnatural pyrrolidine and proline scaffolds. In this review, the application of this reaction to the synthesis of enantiopure organometallic ligands for asymmetric catalysis is presented first. These new EhuPhos ligands can participate in a second generation of 1,3-dipolar reactions that generate an offspring of unnatural proline derivatives that behave as efficient organocatalysts. These densely substituted unnatural l-proline derivatives exhibit distinct features, different to those described for natural l-proline and its derivatives. Finally, several examples of biologically active proline derivatives obtained by means of (3+2) cycloadditions involving azomethine ylides are presented. These applications show the character of privileged structures of these polysubstituted pyrrolidine rings.

An efficient and facile access to highly functionalized pyrrole derivatives

A straightforward and one-pot synthesis of pyrrolo[3,4-c]pyrrole-1,3-diones via Ag(I)-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with N-alkyl maleimide, followed by readily complete oxidation with DDQ, has been successfully developed. Further transformation with alkylamine/sodium alkoxide alcohol solution conveniently afforded novel polysubstituted pyrroles in good to excellent yields. This methodology for highly functionalized pyrroles performed well over a broad scope of substrates. It is conceivable that this efficient construction method for privileged pyrrole scaffolds could deliver more active compounds for medicinal chemistry research.

Bromodomain inhibition shows antitumoral activity in mice and human luminal breast cancer

BET bromodomain inhibitors, which have an antitumoral effect against various solid cancer tumor types, have not been studied in detail in luminal breast cancer, despite the prevalence of this subtype of mammary malignancy. Here we demonstrate that the BET bromodomain inhibitor JQ1 exerts growth-inhibitory activity in human luminal breast cancer cell lines associated with a depletion of the C-MYC oncogene, but does not alter the expression levels of the BRD4 bromodomain protein. Interestingly, expression microarray analyses indicate that, upon JQ1 administration, the antitumoral phenotype also involves downregulation of relevant breast cancer oncogenes such as the Breast Carcinoma-Amplified Sequence 1 (BCAS1) and the PDZ Domain-Containing 1 (PDZK1). We have also applied these in vitro findings in an in vivo model by studying a transgenic mouse model representing the luminal B subtype of breast cancer, the MMTV-PyMT, in which the mouse mammary tumor virus promoter is used to drive the expression of the polyoma virus middle T-antigen to the mammary gland. We have observed that the use of the BET bromodomain inhibitor for the treatment of established breast neoplasms developed in the MMTV-PyMT model shows antitumor potential. Most importantly, if JQ1 is given before the expected time of tumor detection in the MMTV-PyMT mice, it retards the onset of the disease and increases the survival of these animals. Thus, our findings indicate that the use of bromodomain inhibitors is of great potential in the treatment of luminal breast cancer and merits further investigation.

Synthesis of 11C-labeled Kendine 91, a histone deacetylase inhibitor

In the present paper, the synthesis of (11)C-labeled Kendine 91 (a HDAC inhibitor which has shown in vitro and in vivo activity in HCT 116 and MOLT 4 human cancer cell lines) is described for the first time. The radiosynthesis has been approached by reaction of the non-radioactive precursor 6-((3-(4-hydroxyphenyl)-5-phenyl-1H-pyrrole-2-carboxamide))hexanehydroxamic acid with [(11)C]CH(3)I in basic media. Despite the presence of more than one reactive site in the chemical structure of the precursor, acceptable radiochemical yield (8.2±2.1%, decay corrected to the end of bombardment), specific activity (28.2±9.4 GBq/μmol) and radiochemical purity values (>95%) were obtained in reasonably short preparation times (~40 min). Despite the moderate radiochemical yield, final radioactivity and radioactivity concentration values (1.8±0.3 GBq and 180 MBq/ml, respectively) should be sufficient for putative in vivo studies in animals.

Antitumor activity of a small-molecule inhibitor of the histone kinase Haspin

The approval of histone deacetylase inhibitors for treatment of lymphoma subtypes has positioned histone modifications as potential targets for the development of new classes of anticancer drugs. Histones also undergo phosphorylation events, and Haspin is a protein kinase the only known target of which is phosphorylation of histone H3 at Thr3 residue (H3T3ph), which is necessary for mitosis progression. Mitotic kinases can be blocked by small drugs and several clinical trials are underway with these agents. As occurs with Aurora kinase inhibitors, Haspin might be an optimal candidate for the pharmacological development of these compounds. A high-throughput screening for Haspin inhibitors identified the CHR-6494 compound as being one promising such agent. We demonstrate that CHR-6494 reduces H3T3ph levels in a dose-dependent manner and causes a mitotic catastrophe characterized by metaphase misalignment, spindle abnormalities and centrosome amplification. From the cellular standpoint, the identified small-molecule Haspin inhibitor causes arrest in G2/M and subsequently apoptosis. Importantly, ex vivo assays also demonstrate its anti-angiogenetic features; in vivo, it shows antitumor potential in xenografted nude mice without any observed toxicity. Thus, CHR-6494 is a first-in-class Haspin inhibitor with a wide spectrum of anticancer effects that merits further preclinical research as a new member of the family of mitotic kinase inhibitors.

A structure-based virtual screening approach toward the discovery of histone deacetylase inhibitors: identification of promising zinc-chelating groups

The inhibitors of histone deacetylases (HDACs) have drawn a great deal of attention due to their promising potential as small-molecule therapeutics for the treatment of cancer. By means of virtual screening with docking simulations under consideration of the effects of ligand solvation, we were able to identify six novel HDAC inhibitors with IC(50) values ranging from 1 to 100 muM. These newly identified inhibitors are structurally diverse and have various chelating groups for the active site zinc ion, including N-[1,3,4]thiadiazol-2-yl sulfonamide, N-thiazol-2-yl sulfonamide, and hydroxamic acid moieties. The former two groups are included in many drugs in current clinical use and have not yet been reported as HDAC inhibitors. Therefore, they can be considered as new inhibitor scaffolds for the development of anticancer drugs by structure-activity relationship studies to improve the inhibitory activities against HDACs. Interactions with the HDAC1 active site residues responsible for stabilizing these new inhibitors are addressed in detail.