Efficient Synthesis of NewC-Functionalized Macrocyclic Polyamines

The multivalent G-quadruplex (G4)-ligands MultiTASQs allow for versatile click chemistry-based investigations

Chemical biology hinges on multivalent molecular tools that can specifically interrogate and/or manipulate cellular circuitries from the inside. The success of many of these approaches relies on molecular tools that make it possible to visualize biological targets in cells and then isolate them for identification purposes. To this end, click chemistry has become in just a few years a vital tool in offering practically convenient solutions to address highly complicated biological questions. We report here on two clickable molecular tools, the biomimetic G-quadruplex (G4) ligands MultiTASQ and ^azMultiTASQ, which benefit from the versatility of two types of bioorthogonal chemistry, CuAAC and SPAAC (the discovery of which was very recently awarded the Nobel Prize of chemistry). These two MultiTASQs are used here to both visualize G4s in and identify G4s from human cells. To this end, we developed click chemo-precipitation of G-quadruplexes (G4-click-CP) and in situ G4 click imaging protocols, which provide unique insights into G4 biology in a straightforward and reliable manner.

Click-Chemistry-Based Biomimetic Ligands Efficiently Capture G-Quadruplexes In Vitro and Help Localize Them at DNA Damage Sites in Human Cells

Interrogating G-quadruplex (G4) biology at its deepest roots in human cells relies on the design, synthesis, and use of ever smarter molecular tools. Here, we demonstrate the versatility of biomimetic G4 ligands referred to as TASQ (template assembled synthetic G-quartet) in which a biotin handle was incorporated for G4-focused chemical biology investigations. We have rethought the biotinylated TASQ design to make it readily chemically accessible via an efficient click-chemistry-based strategy. The resulting biotinylated, triazole-assembled TASQ, or BioTriazoTASQ, was thus shown to efficiently isolate both DNA and RNA G4s from solution by affinity purification protocols, for identification purposes. Its versatility was then further demonstrated by optical imaging that provided unique mechanistic insights into the actual strategic relevance of G4-targeting strategies, showing that ligand-stabilized G4 sites colocalize with and, thus, are responsible for DNA damage foci in human cells.

Biomimetic, Smart, and Multivalent Ligands for G-Quadruplex Isolation and Bioorthogonal Imaging

G-quadruplexes (G4s) continue to gather wide attention in the field of chemical biology as their prevalence in the human genome and transcriptome strongly suggests that they play key regulatory roles in cell biology. G4-specific, cell-permeable small molecules (G4-ligands) innovatively permit the interrogation of cellular circuitries in order to assess to what extent G4s influence cell fate and functions. Here, we report on multivalent, biomimetic G4-ligands referred to as TASQs that enable both the isolation and visualization of G4s in human cells. Two biotinylated TASQs, BioTASQ and BioCyTASQ, are indeed efficient molecular tools to isolate G4s from mixtures of nucleic acids through simple affinity capture protocols and to image G4s in cells via a biotin/avidin pretargeted imaging system first applied here to G4s, found to be a reliable alternative to in situ click chemistry.

A New pH-Dependent Macrocyclic Rhodamine B-Based Fluorescent Probe for Copper Detection in White Wine

For efficiently measuring copper (II) ions in the acidic media of white wine, a new chemosensor based on rhodamine B coupled to a tetraazamacrocyclic ring (13aneN₄CH₂NH₂) was designed and synthesized by a one-pot reaction using ethanol as a green solvent. The obtained chemosensor was characterized via NMR, UV and fluorescent spectra. It was marked with no color emission under neutral pH conditions, with a pink color emission under acidic conditions, and a magenta color emission under acidic conditions where copper (II) ions were present. The sensitivity towards copper (II) ions was tested and verified over Ca²⁺, Ag⁺, Zn²⁺, Mg²⁺, Co²⁺, Ni²⁺, Fe²⁺, Pb²⁺, Cd²⁺, Fe³⁺, and Mn²⁺, with a detection limit of 4.38 × 10^-8 M in the fluorescence spectrum.

Straightforward synthesis of bis-tetraazacycloalkanes: towards new potential CXCR4 antagonists?

We report herein an efficient and general method for the synthesis of new bismacrocyclic compounds, structural analogues of biscyclam AMD3100, in which the two macrocycles are linked together through carbon atoms of the cycles.

C-Functionalized chiral dioxocyclam and cyclam derivatives with 1,2,3-triazole units: synthesis, complexation properties and crystal structures of copper(ii) complexes

NewC-functionalized dioxocyclam and cyclam derivatives with 1,2,3-triazoles attached to carbon atoms within the skeleton were designed as valuable bifunctional chelators for molecular imaging.

Reinforced cyclam derivatives functionalized on the bridging unit

The introduction of one or two nitriles on the bridge of reinforced cyclams paves the way for the synthesis of new bifunctional chelating agents. X-ray structures of the chelators and of two copper complexes are reported.

Helical self-assembly of 2-(1,4,7,10-tetraazacyclododecan-1-yl)cyclohexan-1-ol (cycyclen)

The title macrocyclic amino alcohol compound, C(14)H(30)N(4)O, is investigated as a solid-state synthon for the design of a self-assembled tubular structure. It crystallizes in a helical column constructed by stereospecific O-H···N and N-H···N interactions. The hydrogen-bonding interactions, dependent upon macrocyclic ring helicity and molecular conformation, link R,R and S,S enantiomers in a head-to-tail fashion, forming a continuous hydrophilic inner core.

DOTAGA-anhydride: a valuable building block for the preparation of DOTA-like chelating agents

A DOTA derivative that contains an anhydride group was readily synthesized by reacting DOTAGA with acetic anhydride and its reactivity was investigated. Opening the anhydride with propylamine led to the selective formation of one of two possible regioisomers. The structure of the obtained isomer was unambiguously determined by 1D and 2D NMR experiments, including COSY, HMBC, and NOESY techniques. This bifunctional chelating agent offers a convenient and attractive approach for labeling biomolecules and, more generally, for the synthesis of a large range of DOTA derivatives. The scope of the reaction was extended to prepare DOTA-like compounds that contained various functional groups, such as isothiocyanate, thiol, ester, and amino acid moieties. This versatile building block was also used for the synthesis of a bimodal tag for SPECT or PET/optical imaging.