Protein-triggered supramolecular disassembly: insights based on variations in ligand location in amphiphilic dendrons.

We use monodisperse dendrons that allow control over functional group presentation to investigate the influence of the location of a ligand on protein-induced disassembly and release of encapsulated small molecules. Based on both experiments and molecular dynamics simulations, we demonstrate that ligand location greatly influences release of guest molecules from the dendron-based supramolecular assembly. We show that a ligand moiety grafted to the dendron periphery is more accessible for the target protein in aqueous solution. On the other hand, the ligand moiety placed at the focal point or at the intermediate layer within the dendritic scaffold is less accessible, since it is surrounded by an environment rich in PEG chains, which hinders binding and even influences nonspecific interactions. We also demonstrate that the specific binding between one ligand and the target protein can destabilize the dendritic assembly. Furthermore, if more ligands are available, multivalent interactions are also possible with extravidin, which speed up disassembly and trigger the release of hydrophobic guests.

Small molecule BODIPY dyes as non-fullerene acceptors in bulk heterojunction organic photovoltaics.

A series of acceptor-donor-acceptor molecules containing terminal BODIPY moieties conjugated through the meso position were synthesized. Deep LUMO energy levels and good visible absorption led to their use as acceptors in bulk heterojunction solar cells. Inverted devices were fabricated, reaching efficiencies as high as 1.51%.

Zwitterionic moieties from the Huisgen reaction: a case study with amphiphilic dendritic assemblies.

Supramolecular nano-assemblies that reduce nonspecific interactions with biological macromolecules, such as proteins, are of great importance for various biological applications. Recently, zwitterionic materials have been shown to reduce nonspecific interactions with biomolecules, owing both to their charge neutrality and their ability to form a strong hydration layer around zwitterions via electrostatic interactions. Here, new triazole-based zwitterionic moieties are presented that are incorporated as the hydrophilic functionalities in facially amphiphilic dendrons. The amphiphilic zwitterionic dendrons spontaneously self-assemble in aqueous solutions forming micelle-type aggregates, which were confirmed by DLS, TEM, and fluorescence techniques. The structural and functional characteristics of the zwitterionic dendrons are also compared with the corresponding charge-neutral PEG-based dendrons and anionic carboxylate-based dendrons. Surface-charge measurements, temperature sensitivity and evaluation of interactions of these assemblies with proteins form the bases for these comparisons.

Temperature-sensitive transitions below LCST in amphiphilic dendritic assemblies: host-guest implications.

Oligo(ethylene glycol)-decorated supramolecular assemblies have been of great interest due to their charge-neutral character and thus their propensity to avoid nonspecific interactions. These systems are known to exhibit a macroscopic temperature-sensitive transition, where the assembly phase-separates from the aqueous phase at higher temperatures. While this so-called lower critical solution temperature (LCST) behavior has been well-studied, there have been no studies on the fate of these supramolecular assemblies below this transition temperature. The work here brings to light the presence of a second, sub-LCST transition, observed well below the LCST of oligo(ethylene glycol) (OEG)-based dendrons, where the host-guest properties of the assembly are significantly altered. This sub-LCST transition is accompanied by changes in the guest encapsulation stability and dynamics of host exchange.

A radical cyclization approach to the formal total syntheses of platencin.

Two different strategies leading to formal total syntheses of platencin are described. The first strategy involving Claisen rearrangement and radical cyclization provides a rapid access to the core structure of platencin, and also use minimum protective-group operations. The second strategy, a protecting group-free route, utilizes a 6-exo-trig radical cyclization and aldol condensation as key steps leading to the formal synthesis of platencin.

Application of an enyne metathesis/Diels-Alder cycloaddition sequence: a new versatile approach to the syntheses of C-aryl glycosides and spiro-C-aryl glycosides.

An efficient approach for the synthesis of a variety of C-aryl and spiro-C-aryl glycosides is described. This diversity-oriented strategy employed here relies on a sequential enyne metathesis to generate the 1,3-diene moiety and Diels-Alder reaction with different dienophiles followed by aromatisation. Whereas cross-enyne metathesis with ethylene gas is used to install the 1,3-diene moiety at the anomeric centre for the synthesis of C-aryl glycosides, an intramolecular enyne metathesis on the sugar enyne is performed to generate the 1,3-diene moiety for the synthesis of spiro-C-aryl glycosides. Efforts to extend this strategy to the synthesis of the core structure of natural C-aryl glycoside gilvocarcin are also described. A combination of both C-aryl and spiro-C-aryl glycosides in the same moiety to combine the features thereof has also been accomplished. A tandem enyne metathesis/Diels-Alder reaction/aromatisation has also been attempted to directly access the C-aryl glycosides in one pot albeit in low yield.

A new versatile strategy for C-aryl glycosides.

A versatile strategy involving a sequential intermolecular enyne metathesis of C-alkynyl glycosides with ethylene, Diels-Alder, and aromatization reactions is successfully developed to provide a range of C-aryl glycosides. [reaction: see text]