Transition metal-mediated synthesis of oxazoles

Among the synthetic methods for the formation of the oxazole ring, transition metal-mediated protocols are the most attractive in terms of selectivity, efficiency and mildness of reaction conditions. In this review we discuss methods for the preparation of oxazoles using transition metal complexes highlighting the key bonds being formed. This reveals critical gaps in the existing literature for the construction of this biologically significant ring system highlighting exciting opportunities for further research

Copper-catalysed C-H functionalisation gives access to 2-aminobenzimidazoles

This paper describes the development, optimisation and exemplification of a copper-catalysed C–H functionalisation to form pharmaceutically relevant 2-aminobenzimidazoles from aryl-guanidines. High throughput screening was used as a tool to identify a catalytically active copper source, DoE was used for reaction optimisation and a range of aryl-guanidines were prepared and exposed to the optimum conditions to afford a range of 2-aminobenzimidazoles in moderate to good yields. The methodology has been applied to the synthesis of Emedastine, a marketed anti-histamine pharmaceutical compound, with the key cyclisation step performed on a gram-scale

The linker domain of the SNARE protein SNAP25 acts as a flexible molecular spacer that ensures efficient S-acylation

S-Acylation of the SNARE protein SNAP25 (synaptosomeassociated protein of 25 kDa) is mediated by a subset of Golgi zinc finger DHHC-type palmitoyltransferase (zDHHC) enzymes, particularly zDHHC17. The ankyrin repeat domain of zDHHC17 interacts with a short linear motif known as the zDHHC ankyrin repeat- binding motif (zDABM) in SNAP25 ( 112VVASQP 117), which is downstream of its S-acylated, cysteine-rich domain ( 85CGLCVCPC 92). Here, we investigated the importance of a flexible linker region (amino acids 93-111, referred to hereafter as the “mini-linker” region) that separates the zDABM and S-acylated cysteines in SNAP25. Shortening the mini-linker did not affect the SNAP25-zDHHC17 interaction but blocked S-acylation. Insertion of additional flexible glycine-serine repeats had no effect on S-acylation, but extended and rigid alanine-proline repeats perturbed it. A SNAP25 mutant in which the mini-linker region was substituted with a flexible glycine-serine linker of the same length underwent efficient S-acylation. Furthermore, this mutant displayed the same intracellular localization as WT SNAP25, indicating that the amino acid composition of the mini-linker is not important for SNAP25 localization. Using the results of previous peptide array experiments, we generated a SNAP25 mutant predicted to have a higher-affinity zDABM. This mutant interacted with zDHHC17 more strongly but was S-acylated with reduced efficiency in HEK293T cells, implying that a lower-affinity interaction of the SNAP25 zDABM with zDHHC17 is optimal for S-acylation efficiency. These results show that amino acids 93-111 in SNAP25 act as a flexible molecular spacer that ensures efficient coupling of the SNAP25-zDHHC17 interaction and S-acylation of SNAP25

Microwave-assisted synthesis of 3-aminobenzo[b]thiophene scaffolds for the preparation of kinase inhibitors

Microwave irradiation of 2-halobenzonitriles and methyl thioglycolate in the presence of triethylamine in DMSO at 130 °C provides rapid access to 3-aminobenzo[b]thiophenes in 58–96% yield. This transformation has been applied in the synthesis of the thieno[2,3-b]pyridine core motif of LIMK1 inhibitors, the benzo[4,5]thieno[3,2-e][1,4]diazepin-5(2H)-one scaffold of MK2 inhibitors and a benzo[4,5]thieno[3,2-d]pyrimidin-4-one inhibitor of the PIM kinases

C–H arylation of heterocyclic N oxides through in-situ diazotisation of anilines without added promoters : a green and selective coupling process

A green and selective method for the generation of bi-aryl compounds through C—H arylation of heterocyclic N-oxides is presented in which the addition of ascorbic acid as a promoter is not required for either the generation of an aryldiazonium species or the subsequent arylation. Reaction conditions were optimized through Multivariate Data Analysis, including Orthogonal Projections to Latent Structures (OPLS) and Design of Experiments (DoE) methodologies resulting in further sustainability improvements, and were then applied to a range of substrates to establish the scope and limitations of the process. The reaction was studied using in-situ infra-red spectroscopy and a mechanism is presented that accounts for the available data from this and previous studies. The reaction was also per-formed on a multigram scale, with calorimetry studies to support further scale-up of this promoter-free transformation

Advancements in the development of non-BET bromodomain chemical probes

The bromodomain and extra terminal (BET) family of bromodomain‐containing proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of high‐quality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 non‐BET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new non‐BET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the non‐BET bromodomains as tractable therapeutic targets

Solution phase, solid state, and theoretical investigations on the MacMillan imidazolidinone

A combination of soln. phase NMR, X-ray crystallog. studies, and DFT calcns. provide a consistent structural conformation for iminium ions derived from the MacMillan imidazolidinone

Oxidation of primary amines to ketones

A simple method for the oxidn. of primary amines to the corresponding ketones in the presence of both moisture and air is described. Treatment of an amine with benzoyl peroxide in the presence of Cs2CO3, followed by warming of the hydroxylamine product to 50-70° leads directly to the ketone. The method is shown to be effective for both benzylic and aliph. substrates. [on SciFinder(R)

Stereoselective synthesis of alkylidene phthalides

The N,O-diacylhydroxylamine derivative 4 has been prepared and its reactivity with nucleophiles investigated. On reaction with lithium enolates of cyclic or acyclic ketones, 4 is converted stereoselectively to the corresponding alkylidene phthalide. The stereochemical outcome of the transformation can be modified by changing the polarity of the reaction medium and the products isomerized under acidic conditions

Small molecules and their roles in effective pre-clinical target validation

As demonstrated in multiple historical analyses, there are two main causes of clinical attrition; firstly drugs are not efficacious, and secondly they cause unacceptable toxicity, both of which can be the result of poor pre-clinical target validation. Target validation, one of the early stages of a drug discovery program, is the process of (in) validating a drug target to ensure it is significant to the intended disease, and unlikely to drive undesired toxicity. Target validation is vital in preventing late stage failures in the clinic and, if done effectively, can save pharmaceutical companies a great deal of time and money. As such, target validation is treated extremely seriously, as demonstrated by the formation of public - private partnerships, such as Open Targets, aimed to provide evidence of biological validity and the possible likelihood of pharmacological intervention. Central to the variety of molecular tools available for use in target validation are high quality small molecules called chemical probes