1,4,5-Trisubstituted Imidazole-Based p53-MDM2/MDMX Antagonists with Aliphatic Linkers for Conjugation with Biological Carriers.

The tumor suppressor protein p53, the "guardian of the genome", is inactivated in nearly all cancer types by mutations in the TP53 gene or by overexpression of its negative regulators, oncoproteins MDM2/MDMX. Recovery of p53 function by disrupting the p53-MDM2/MDMX interaction using small-molecule antagonists could provide an efficient nongenotoxic anticancer therapy. Here we present the syntheses, activities, and crystal structures of the p53-MDM2/MDMX inhibitors based on the 1,4,5-trisubstituted imidazole scaffold which are appended with aliphatic linkers that enable coupling to bioactive carriers. The compounds have favorable properties at both biochemical and cellular levels. The most effective compound 19 is a tight binder of MDM2 and activates p53 in cancer cells that express the wild-type p53, leading to cell cycle arrest and growth inhibition. Crystal structures reveal that compound 19 induces MDM2 dimerization via the aliphatic linker. This unique dimerization-binding mode opens new prospects for the optimization of the p53-MDM2/MDMX inhibitors and conjugation with bioactive carriers.

Leuckart-Wallach Route Toward Isocyanides and Some Applications.

Isocyanide-based multicomponent reactions (IMCR) are among the most important chemical reactions to efficiently generate molecular diversity and have found widespread use in industry and academia. Generally, isocyanides are synthesized in 1-2 steps starting from primary amines. Here, we provide experimental detail on an alternative approach toward formamides and, thus, isocyanides via the Leuckart-Wallach reaction in an improved variation. The resulting >50 synthesized and characterized formamides are useful starting materials for IMCR, as well as other chemistries. The advantage of using the Leuckart-Wallach pathway to formamides and isocyanides is the lower price, on average, of the starting materials, as well as their differential and complementary structural diversity, as compared to the primary amine pathway.

MCR synthesis of a tetracyclic tetrazole scaffold.

Scaffold diversity is key in the ongoing exercise of discovery of novel bioactive compounds using high throughput screening (HTS). Based on the Ugi tetrazole synthesis we have designed novel bi- and tri-cyclic scaffolds featuring interesting pharmacophore properties. The compounds of the scaffold (B) are synthesizable in large diversity and numbers in two steps using (hetero)phenylethylamines, HN3, oxo components and iscyanoacetaldehyde(dimethylacetale). The chemistry is amenable to parallel synthesis and is used to enhance and fill the screening decks of the European Lead factory (ELF). Here, we are reporting full experimental details, scope and limitations of the reaction, cheminformatic analysis and the 3D structures of selected compounds.

A universal isocyanide for diverse heterocycle syntheses.

Novel scaffolds are of uttermost importance for the discovery of functional material. Three different heterocyclic scaffolds easily accessible from isocyanoacetaldehyde dimethylacetal 1 by multicomponent reaction (MCR) are described. They can be efficiently synthesized by a Ugi tetrazole multicomponent reaction of 1. We discuss the synthesis, 3D structures, and other physicochemical properties.

Discovery of highly potent p53-MDM2 antagonists and structural basis for anti-acute myeloid leukemia activities.

The inhibition of p53-MDM2 interaction is a promising new approach to non-genotoxic cancer treatment. A potential application for drugs blocking the p53-MDM2 interaction is acute myeloid leukemia (AML) due to the occurrence of wild type p53 (wt p53) in the majority of patients. Although there are very promising preclinical results of several p53-MDM2 antagonists in early development, none of the compounds have yet proven the utility as a next generation anticancer agent. Herein we report the design, synthesis and optimization of YH239-EE (ethyl ester of the free carboxylic acid compound YH239), a potent p53-MDM2 antagonizing and apoptosis-inducing agent characterized by a number of leukemia cell lines as well as patient-derived AML blast samples. The structural basis of the interaction between MDM2 (the p53 receptor) and YH239 is elucidated by a co-crystal structure. YH239-EE acts as a prodrug and is the most potent compound that induces apoptosis in AML cells and patient samples. The observed superior activity compared to reference compounds provides the preclinical basis for further investigation and progression of YH239-EE.

Transient protein states in designing inhibitors of the MDM2-p53 interaction.

Reactivation of p53 by release of the functional protein from its inhibition by MDM2 provides an efficient, nongenotoxic approach to a wide variety of cancers. We present the cocrystal structures of two complexes of MDM2 with inhibitors based on 6-chloroindole scaffolds. Both molecules bound to a distinct conformational state of MDM2 with nM-µM affinities. In contrast to other structurally characterized antagonists, which mimic three amino acids of p53 (Phe19, Trp23, and Leu26), the compounds induced an additional hydrophobic pocket on the MDM2 surface and unveiled a four-point binding mode. The enlarged interaction interface of the inhibitors resulted in extension of small molecules binding toward the "lid" segment of MDM2 (residues 19-23)--a nascent element that interferes with p53 binding. As supported by protein engineering and molecular dynamics studies, employing these unstable elements of MDM2 provides an efficient and yet unexplored alternative in development of MDM2-p53 association inhibitors.

Various cyclization scaffolds by a truly Ugi 4-CR.

Efficient access to a large chemical space based on new scaffolds with defined 3D conformations and highly variable in the side chains is needed to find novel functional materials. Four heterocyclic scaffolds based on a four component Ugi reaction of α-amino acids, oxo components, isocyanides and primary or secondary amines suitably functionalized are described. A handful of examples are described for each scaffold.

Tricycles by a new Ugi variation and Pictet-Spengler reaction in one pot.

Subsequent mild cyclization of aromatic substrates by Pictet-Spengler condensation stereoselectively gave new tricyclic compounds. Examples are described in decent yields over two steps in one pot, and a crystal structure is also presented to support the proposed structures.

Multicomponent synthesis of diverse 1,4-benzodiazepine scaffolds.

The 1,4-benzodiazepine (BDZ) scaffold is of particular interest in drug design due to a balanced ensemble of beneficial physicochemical properties including a semirigid and compact diazepine ring with spatial placements of several substituents, combined with low number of rotatable bonds, hydrogen bond donors and acceptors, and intermediate lipophilicity. As an alternative to traditional multistep sequential syntheses, we designed routes employing one-pot MCRs to accelerate access diverse BDZ scaffolds in two or three steps.

P53 mdm2 inhibitors.

The protein-protein interaction (PPI) between p53 and its negative regulator MDM2 comprises one of the most important and intensely studied PPI's involved in preventing the initiation of cancer. The interaction between p53 and MDM2 is conformation-based and is tightly regulated on multiple levels. Due to the Angstrom level structural insight there is a reasonable understanding of the structural requirements needed for a molecule to bind to MDM2 and successfully inhibit the p53/MDM2 interaction. The current review summarizes the binding characteristics of the different disclosed small molecules for inhibition of MDM2 with a co-crystal structure. Synthetic access to these compounds as well as their derivatives are described in detail.

Enabling large-scale design, synthesis and validation of small molecule protein-protein antagonists.

Although there is no shortage of potential drug targets, there are only a handful known low-molecular-weight inhibitors of protein-protein interactions (PPIs). One problem is that current efforts are dominated by low-yield high-throughput screening, whose rigid framework is not suitable for the diverse chemotypes present in PPIs. Here, we developed a novel pharmacophore-based interactive screening technology that builds on the role anchor residues, or deeply buried hot spots, have in PPIs, and redesigns these entry points with anchor-biased virtual multicomponent reactions, delivering tens of millions of readily synthesizable novel compounds. Application of this approach to the MDM2/p53 cancer target led to high hit rates, resulting in a large and diverse set of confirmed inhibitors, and co-crystal structures validate the designed compounds. Our unique open-access technology promises to expand chemical space and the exploration of the human interactome by leveraging in-house small-scale assays and user-friendly chemistry to rationally design ligands for PPIs with known structure.

The p53-MDM2/MDMX axis - A chemotype perspective.

The protein-protein interaction (PPI) of the tumor suppressor p53 and its negative regulator MDM2 consists of the most intense studied PPI with a group of small molecular weight antagonists described and many more disclosed in patent literature. Due to the Å-level structural insight into p53 interaction with MDM2 there is a reasonable understanding of the requirements of the molecules to bind. In contrast and despite the very close homology and 3-D similarity no potent MDMX antagonist has been disclosed up to date. The current review summarizes the different disclosed chemotypes for MDM2 including a discussion of the cocrystal structures. Structures and approaches to reconstitute functional p53 from mutated p53 are presented. Finally new screening methods and recent biotech deals based on p53 are discussed.

(-)-Bacillamide C: the convergent approach.

The newly discovered natural product bacillamide C and several derivatives were convergently synthesized for the first time and in only three steps. The key transformation constitutes a thiazole Ugi multicomponent reaction. These compounds will serve to elucidate chemical biology and SAR of this potent anti-algae natural product and shows the synthetic pathway to related natural products.