Process Development of a Novel Azetidinyl Ketolide Antibiotic

Synthetic Strategies, Reactivity and Applications of 1,5-Naphthyridines

This review covers the synthesis and reactivity of 1,5-naphthyridine derivatives published in the last 18 years. These heterocycles present a significant importance in the field of medicinal chemistry because many of them exhibit a great variety of biological activities. First, the published strategies related to the synthesis of 1,5-naphthyridines are presented followed by the reactivity of these compounds with electrophilic or nucleophilic reagents, in oxidations, reductions, cross-coupling reactions, modification of side chains or formation of metal complexes. Finally, some properties and applications of these heterocycles studied during this period are examined.

Deprotection of N-Boc Groups under Continuous-Flow High-Temperature Conditions

The scope of thermolytic, N-Boc deprotection was studied on 26 compounds from the Pfizer compound library, representing a diverse set of structural moieties. Among these compounds, 12 substrates resulted in clean (≥95% product) deprotection, and an additional three compounds gave ≥90% product. The thermal de-Boc conditions were found to be compatible with a large number of functional groups. A combination of computational modeling, statistical analysis, and kinetic model fitting was used to support an initial, slow, and concerted proton transfer with release of isobutylene, followed by a rapid decarboxylation. A strong correlation was found to exist between the electrophilicity of the N-Boc carbonyl group and the reaction rate.

Nature nurtures the design of new semi-synthetic macrolide antibiotics

Erythromycin and its analogs are used to treat respiratory tract and other infections. The broad use of these antibiotics during the last 5 decades has led to resistance that can range from 20% to over 70% in certain parts of the world. Efforts to find macrolides that were active against macrolide-resistant strains led to the development of erythromycin analogs with alkyl-aryl side chains that mimicked the sugar side chain of 16-membered macrolides, such as tylosin. Further modifications were made to improve the potency of these molecules by removal of the cladinose sugar to obtain a smaller molecule, a modification that was learned from an older macrolide, pikromycin. A keto group was introduced after removal of the cladinose sugar to make the new ketolide subclass. Only one ketolide, telithromycin, received marketing authorization but because of severe adverse events, it is no longer widely used. Failure to identify the structure-relationship responsible for this clinical toxicity led to discontinuation of many ketolides that were in development. One that did complete clinical development, cethromycin, did not meet clinical efficacy criteria and therefore did not receive marketing approval. Work on developing new macrolides was re-initiated after showing that inhibition of nicotinic acetylcholine receptors by the imidazolyl-pyridine moiety on the side chain of telithromycin was likely responsible for the severe adverse events. Solithromycin is a fourth-generation macrolide that has a fluorine at the 2-position, and an alkyl-aryl side chain that is different from telithromycin. Solithromycin interacts at three sites on the bacterial ribosome, has activity against strains resistant to older macrolides (including telithromycin), and is mostly bactericidal. Pharmaceutical scientists involved in the development of macrolide antibiotics have learned from the teachings of Professor Satoshi Omura and progress in this field was not possible without his endeavors.

Synthesis and biological evaluation of negative allosteric modulators of the Kv11.1(hERG) channel

We synthesized and evaluated a series of compounds for their allosteric modulation at the Kv11.1 (hERG) channel. Most compounds were negative allosteric modulators of [(3)H]dofetilide binding to the channel, in particular 7f, 7h-j and 7p. Compounds 7f and 7p were the most potent negative allosteric modulators amongst all ligands, significantly increasing the dissociation rate of dofetilide in the radioligand kinetic binding assay, while remarkably reducing the affinities of dofetilide and astemizole in a competitive displacement assay. Additionally, both 7f and 7p displayed peculiar displacement characteristics with Hill coefficients significantly distinct from unity as shown by e.g., dofetilide, further indicative of their allosteric effects on dofetilide binding. Our findings in this investigation yielded several promising negative allosteric modulators for future functional and clinical research with respect to their antiarrhythmic propensities, either alone or in combination with known Kv11.1 blockers.