Nisamycin, a new manumycin group antibiotic from Streptomyces sp. K106. I. Taxonomy, fermentation, isolation, physico-chemical and biological properties

Simultaneous Covalent Modification of K-Ras(G12D) and K-Ras(G12C) with Tunable Oxirane Electrophiles

Owing to their remarkable pharmaceutical properties compared to those of noncovalent inhibitors, the development of targeted covalent inhibitors (TCIs) has emerged as a powerful method for cancer treatment. The K-Ras mutant, which is prevalent in multiple cancers, has been confirmed to be a crucial drug target in the treatment of various malignancies. However, although the K-Ras(G12D) mutation is present in up to 33% of K-Ras mutations, no covalent inhibitors targeting K-Ras(G12D) have been developed to date. The relatively weak nucleophilicity of the acquired aspartic acid (12D) residue in K-Ras may be the reason for this. Herein, we present the first compound capable of covalently engaging both K-Ras(G12D) and K-Ras(G12C) mutants. Proteome profiling revealed that this compound effectively conjugates with G12C and G12D residues, modulating the protein functions in situ. These findings offer a unique pathway for the development of novel dual covalent inhibitors.

Design and introduction of quaternary ammonium hydroxide-functionalized graphene oxide quantum dots as a pseudo-homogeneous catalyst for epoxidation of α,β-unsaturated ketones

In present work, design and synthesis of a novel pseudo-homogeneous catalyst is described. For this purpose, amine-functionalized graphene oxide quantum dots (N-GOQDs) were prepared from graphene oxide (GO) by a facile one-step oxidative fragmentation approach. The prepared N-GOQDs were then modified with quaternary ammonium hydroxide groups. Various characterization techniques clearly revealed that the quaternary ammonium hydroxide-functionalized GOQDs (N-GOQDs/OH^-) have been successfully synthesized. TEM image revealed that the GOQDs particles are almost regularly spherical in shape and mono-dispersed with particle sizes < 10 nm. The efficiency of the synthesized N-GOQDs/OH^- as a pseudo-homogeneous catalyst in epoxidation of α,β-unsaturated ketones in the presence of aqueous H₂O₂ as an oxidant at room temperature was investigated. The corresponding epoxide products were obtained in good to high yields. This procedure has the advantages of a green oxidant, high yields, involvement of non-toxic reagents and reusability of the catalyst without discernible loss in activity.

Peroxide- and transition metal-free electrochemical synthesis of α,β-epoxy ketones

A novel electrochemical method for the synthesis of α,β-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,β-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,β-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.