Expedient synthesis of trifunctional oligoethyleneglycol-amine linkers and their use in the preparation of PEG-based branched platforms

We designed a convergent synthesis pathway that provides access to trifunctional oligoethyleneglycol-amine (OEG-amine) linkers. By applying the reductive coupling of a primary azide to bifunctional OEG-azide precursors, the corresponding symmetrical dialkylamine bearing two homo-functional end chain groups and a central nitrogen was obtained. These building blocks bear minimal structural perturbation compared to the native OEG backbone which makes them attractive for biomedical applications. The NMR investigations of the mechanism process reveal the formation of nitrile and imine intermediates which can react with the reduced free amine form. Additionally, these trifunctional OEG-amine linkers were employed in a coupling reaction to afford branched multifunctional PEG dendrons which are molecularly defined. These discrete PEG-based dendrons (n = 16, 18 and 36) could be useful for numerous applications where multivalency is required.

Carbohydrates as potentially versatile core subcarriers for multivalent immunogens

Synthetic multivalent glycoclusters that carry carbohydrate antigen epitopes have been recognized as promising candidates for the development of carbohydrate based vaccines. Here we describe a convergent strategy for the synthesis of conjugation-ready multivalent glycoclusters using sugars as versatile core subcarriers. d-Glucose and gentiobiose were converted into poly-alkyne functionalized cores which were then decorated with an azide bearing model ligand d-glucose using click chemistry, to form structurally well-defined tetra- and heptavalent glycoclusters. Each cluster was conjugated to a model protein bovine serum albumin (BSA) by squaric acid chemistry. Carbohydrate clusters can be prepared in a variety of sizes and spatial arrangements by altering the structure and configuration of the core, depending on the mono-, or oligosaccharides used for their assembly. It is suggested that the use of carbohydrate as core subcarriers provides an opportunity to tailor the size and topology of antigens and modify multivalent presentation of immunogens in a way to optimize cluster effect for stronger immunoreactivity.

Synthesis, antiviral, cytotoxic and cytostatic evaluation of N 1-(phosphonoalkyl)uracil derivatives

Abstract

A series of N¹-(phosphonoalkyl)uracils was prepared in a two-step reaction sequence from ω-aminoalkylphosphonates and (E)-3-ethoxyacryloyl isocyanate followed by the uracil ring closure. Under standard conditions (NCS; NBS; I₂/CAN) all N¹-(phosphonoalkyl)uracils were transformed into the respective 5-halogeno derivatives to be later benzoylated at N3. All compounds were evaluated in vitro for activity against a broad variety of DNA and RNA viruses. One compound was slightly active against human cytomegalovirus in HEL cell cultures (EC₅₀ = 45 μM) while another showed weak activity against varicella-zoster virus (TK⁺ VZV strain OKA and TK⁻ VZV strain 07-1) with EC₅₀ = 43 and 53 µM, respectively. In addition, several compounds exhibited noticeable inhibitory effects on the proliferation of human cervical carcinoma cells (HeLa) at a concentration lower than 200 μM.

Graphical abstract

Phosphonoxins III: synthesis of α-aminophosphonate analogs of antifungal polyoxins with anti-Giardia activity

A synthesis of α-aminophosphonate analogs of polyoxins, termed phosphonoxin C1, C2, and C3, has been achieved. The key step was the addition of lithium dimethyl phosphite to the aldehyde of a protected threose derivative. α-Hydroxyphosphonate analogs C4 and C5 were also obtained by taking advantage of an unprecedented conversion of an azide to hydroxyl during treatment with hydrogen on palladium on carbon. The resulting phosphonoxin C5 inhibited the growth of an intestinal protozoan, Giardia lamblia, at low micromolar concentration.

Assembly of dithiocarbamate-anchored monolayers on gold surfaces in aqueous solutions

Dithiocarbamates (DTCs) can be formed by the in situ condensation of polar alkylamines with CS 2, and assembled into dithiocarbamate-anchored monolayers (DAMs) on Au substrates in aqueous solutions. Primary and secondary amines can both be used to prepare DTCs, but have significant differences in their reactivities and product stabilities. Ultraviolet absorption spectroscopy provides a convenient method for monitoring in situ DTC formation as well as the formation of potential byproducts. The kinetics of DAM assembly on Au substrates as measured by second harmonic generation (SHG) indicated first-order rate processes and saturation coverages similar to those of alkanethiols on Au. However, the rate of adsorption did not change with DTC concentration in a manner expected of Langmuir kinetics, and is attributed to the competitive adsorption of alkylammonium counterions to the freshly oxidized Au substrate. These analyses establish a practical range of conditions for preparing DAMs from polar amines using in situ DTC formation.