In Planta, In Vitro and In Silico Studies of Chiral N6-Benzyladenine Derivatives: Discovery of Receptor-Specific S-Enantiomers with Cytokinin or Anticytokinin Activities

N6-(5-Phenylpentan-1-yl)adenine-A New Non-competitive Receptor-Specific Anti-cytokinin

For the first time, N6-(5-phenylpentan-1-yl)adenine, a synthetic adenine derivative with a receptor-specific anticytokinin effect, was obtained. This compound exhibits a pronounced anticytokinin effect, reducing cytokinin-induced expression of the GUS reporter gene when interacting with the cytokinin receptor CRE1/AHK4 of the model plant Arabidopsis thaliana. This effect manifests itself much weaker with the related AHK2 receptor and is not observed at all with the AHK3 receptor. We showed that N6-(5-phenylpentan-1-yl)adenine does not bind to the ligand-binding sites of the Arabidopsis cytokinin receptors, which does not allow it to be classified as a true cytokinin antagonist. Despite the currently unknown mechanism of action, this compound may find its use as a component of plant growth regulators. Like true anticytokinins, it enhances root growth of Arabidopsis seedlings, apparently suppressing the action of endogenous cytokinins on the "root" receptor CRE1/AHK4.

Intramolecular Hydrogen Bonding in N6-Substituted 2-Chloroadenosines: Evidence from NMR Spectroscopy

Two forms were found in the NMR spectra of N⁶-substituted 2-chloroadenosines. The proportion of the mini-form was 11-32% of the main form. It was characterized by a separate set of signals in COSY, ¹⁵N-HMBC and other NMR spectra. We assumed that the mini-form arises due to the formation of an intramolecular hydrogen bond between the N7 atom of purine and the N⁶-CH proton of the substituent. The ¹H,¹⁵N-HMBC spectrum confirmed the presence of a hydrogen bond in the mini-form of the nucleoside and its absence in the main form. Compounds incapable of forming such a hydrogen bond were synthesized. In these compounds, either the N7 atom of the purine or the N⁶-CH proton of the substituent was absent. The mini-form was not found in the NMR spectra of these nucleosides, confirming the importance of the intramolecular hydrogen bond in its formation.

State of art in the chemistry of nucleoside-based Pt(II) complexes

After the fortuitous discovery of the anticancer properties of cisplatin, many Pt(II) complexes have been synthesized, to obtain less toxic leads which could overcome the resistance phenomena. Given the importance of nucleosides and nucleotides as antimetabolites, studying their coordinating properties towards Pt(II) ions is challenging for bioorganic and medicinal chemistry. This review aims to describe the results achieved so far in the aforementioned field, paying particular attention to the synthetic aspects, the chemical-physical characterization, and the biological activities of the nucleoside-based Pt(II) complexes.

Perception, Transduction and Crosstalk of Auxin and Cytokinin Signals

Auxins and cytokinins are considered the most important plant hormones, responsible for fundamental traits of the plant organism [...].