During the past decade, there has been growing interest in the structure, recognition, and function of DNA G-quadruplexes. The best-studied example is the human telomeric quadruplex, which is associated with the inhibition of telomere elongation by telomerase, an enzyme up-regulated in cancer cells.1 Furthermore, a large number of other putative quadruplex forming sequences have been identified in the human genome.2 We have recently identified a quadruplex forming sequence in the promoter of the c-kit oncogene with potential to regulate the expression of the c-kit gene at the transcription level. 3 We have demonstrated that this quadruplex predominantly exists in a parallel conformation in vitro under near physiological conditions. In contrast, the human telomeric quadruplex has been shown to adopt different conformations in the presence of either sodium or potassium. Structural studies have reported that the human telomeric quadruplex can exist as a parallel, 4 antiparallel,5 or even a mixed-type hybrid structure.6 Hitherto, chemists have been addressing the design of small molecule ligands that selectively recognize quadruplex DNA in preference to double-stranded DNA. However, owing to the increasing number of quadruplexes being identified in the human genome, an emerging goal is to elucidate quadruplex recognition by small molecules in order to design ligands that can discriminate between quadruplex sequences and/or quadruplex folds. A number of other classes of macrocyclic molecules have been reported in the literature that have shown good potential to bind quadruplexes.7Herein, we report on the quadruplex binding properties of oxazole-based peptide macrocycles of general structure 1 (Figure 1). In particular, we have studied their interaction with the c-kit quadruplex in comparison to the human telomeric quadruplex. Structural studies on related, biologically active cyclopeptides using molecular modeling and X-ray crystallography studies concluded that macrocycles of structure 1 are generally planar.8 This information together with a consideration of the size complementarity led us to reason that such structures have potential to recognize quadruplexes via interactions with the top tetrad. The macrocycles 1a-d are chiral and functionalized with alkylamines to provide water solubility and potentially also participate in favorable interactions with the DNA scaffold. As part of the study we have investigated the influence of stereochemical variations as well as the importance of the lateral side chains on quadruplex recognition and stabilization.Macrocycles of general structure 1 were synthesized by assembly of three amino acid building blocks (2, Figure 1) It is noteworthy that while ligands 1a-d all bind quadruplex DNA, none of the macrocyles showed detectable binding to double-stranded DNA, even at high ligand concentration (300 μM), thus this class of molecules is highly selective for quadruplex as compared to duplex.The enantiomers 1a,b were found to bind hTelo with comparable dissociation constants (K D...

[reaction: see text] An efficient one-pot sequence comprising a homolytic aromatic substitution followed by an ionic Horner-Wadsworth-Emmons olefination for the preparation of a small library of alpha,beta-unsaturated oxindoles is presented. Microwave-induced heating is used to conduct these reactions. The homolytic aromatic substitution is mediated by the persistent radical effect.

[reaction: see text] Alkoxyamines A, which are readily prepared from commercially available starting materials, undergo efficient thermal radical carboaminoxylations onto various nonactivated alkenes to provide 1,4-functionalized malonates B in good to excellent yields. The experiments are very easy to conduct. The carboaminoxylations can be combined with radical cyclization and fragmentation processes.

The search for small-molecule ligands of biological targets remains a challenge with major implications for both fundamental studies and drug discovery. [1] We are interested in the discovery of small molecules that specifically interact with regulatory nucleic acid elements. Such molecules have the potential to alter the expression of particular genes and thus influence cellular functions.Certain guanine-rich (G-rich) regions in genomic DNA can form four-stranded structures, called G quadruplexes, which have emerged as biologically important elements.[2] Gquadruplex formation has been linked to cancer-related biology, most notably by remodeling of the telomere structure or by the regulation of oncogenic expression.[3] The two key challenges in the design of small-molecule[4] ligands for quadruplex DNA are: 1) to attain specificity for G-quadruplex-forming sequences over duplex DNA and 2) to achieve specificity for a given G-quadruplex structure and/or G-quadruplex-forming sequence. The latter criterion has become more important in the light of the recently revealed prevalence of G-quadruplex-forming sequences in the human genome,[5a,b] and particularly in promoter regions. [5c] Although G quadruplexes all contain G quartets, there is considerable scope for structural variations within the loop and groove regions, [6] suggesting that specificity in the molecular recognition of a quadruplex is attainable. However, the rational design of quadruplexbinding molecules requires a good understanding of the interactions between the ligand and its host. Owing to the paucity of structural data and the dynamic nature of G quadruplexes, combinatorial searches are appealing.Herein, we report on a study that employs a dynamic combinatorial approach to explore the differential recognition of G-quadruplex targets by closely related small molecules. Dynamic combinatorial chemistry (DCC) is a powerful approach for the rapid identification of binders for small molecules and biological targets. [7] Owing to its adaptive nature, small changes in the composition of a dynamic combinatorial library (DCL) upon introduction of a ** This study was supported by the Cancer Research UK, the EU, and EPSRC. We thank the EPSRC Mass Spectrometry Service for mass analysis.

Calpain overactivation has been implicated in a variety of pathological disorders including ischemia/reperfusion injury, cataract formation, and neurodegenerative diseases such as Alzheimer's disease (AD). Herein we describe our efforts leading to the identification of ketoamide-based 2-(3-phenyl-1H-pyrazol-1-yl)nicotinamides as potent and reversible inhibitors of calpain with high selectivity versus related cysteine protease cathepsins, other proteases, and receptors. Broad efficacy in a set of preclinical models relevant to AD suggests that inhibition of calpain represents an attractive approach with potential benefit for the treatment of AD.

Affinität ist Einstellungssache: Mithilfe dynamischer kombinatorischer Chemie wurden die Auswirkungen chemischer Modifizierungen auf die Bindung eines Oxazol‐Peptid‐Makrocyclus an den DNA‐G‐Quadruplex untersucht. Zwei dynamische Molekülbibliotheken, eine mit kationischen und eine mit Kohlenhydratmotiven, wurden an Nucleinsäuren mit verschiedenartigen Strukturen getestet (siehe Schema; die farbigen Formen stehen für Kationen oder Kohlenhydrate).

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Dysregulation of calpains 1 and 2 has been implicated in a variety of pathological disorders including ischemia/reperfusion injuries, kidney diseases, cataract formation, and neurodegenerative diseases such as Alzheimer's disease (AD). 2-(3-Phenyl-1)-pyrazol-1-yl)nicotinamides represent a series of novel and potent calpain inhibitors with high selectivity and efficacy. However, carbonyl reduction leading to the formation of the inactive hydroxyamide was identified as major metabolic liability in monkey and human, a pathway not reflected by routine absorption, distribution, metabolism, and excretion (ADME) assays. Using cytosolic clearance as a tailored ADME assay coupled with hepatocyte metabolism enabled the identification of analogues with enhanced stability against carbonyl reduction. These efforts led to the identification of P1' modified calpain inhibitors with significantly improved pharmacokinetic profile including P1'-methoxyamide as potential candidate compound for non-central nervous system indications.