The Diels–Alder reaction that involves a nitrogen atom in the diene or dienophile is termed the aza-Diels–Alder reaction.

A single G-quadruplex forming sequence from the human telomere can adopt six distinct topologies that are inter-convertible under physiological conditions. This presents challenges to design ligands that show selectivity and specificity towards a particular conformation. Additional complexity is introduced in differentiating multimeric G-quadruplexes over monomeric species, which would be able to form in the single-stranded 3′ ends of telomeres. A few ligands have been reported that bind to dimeric quadruplexes, but their preclinical pharmacological evaluation is limited. Using multidisciplinary approaches, we identified a novel quinoline core ligand, BMPQ-1, which bound to human telomeric G-quadruplex multimers over monomeric G-quadruplexes with high selectivity, and induced the formation of G-quadruplex DNA along with the related DNA damage response at the telomere. BMPQ-1 reduced tumor cell proliferation with an IC₅₀ of ∼1.0 μM and decreased tumor growth rate in mouse by half. Biophysical analysis using smFRET identified a mixture of multiple conformations coexisting for dimeric G-quadruplexes in solution. Here, we showed that the titration of BMPQ-1 shifted the conformational ensemble of multimeric G-quadruplexes towards (3+1) hybrid-2 topology, which became more pronounced as further G-quadruplex units are added.

LJTP3, a novel small-molecule fluorescent probe, achieves high-sensitivity Hg²⁺ detection in live plants, enabling spatiotemporal subcellular tracking and 3D root imaging of Hg²⁺ distribution.

1. Abstract A novel series of N-nitro urea derivatives 6a-w containing various amino acid ethyl esters were conveniently synthesized via three steps including nitration, carbamic chlorination, and aminolysis reactions. The structures of all compounds prepared have been confirmed by ¹H NMR, IR spectroscopy and elemental analyses, and a part has been identified by ¹³C NMR . The preliminary bioassay indicates that some of the target compounds possesses moderate herbicidal activity against Echinochloa crusgalli and Amaranthus albus. However, some of the title compounds presented high plant growth regulating activity against rice.

2. Keywords: Amino Acid Ethyl Ester; Synthesis × N-Nitro Urea Derivative; Herbicidal Activity