Preparation of pyridopyrazines through tandem Pd-catalyzed C-N/C-C coupling reactions of Ugi adducts.

A Pd-catalyzed selective tandem cyclization of the Ugi adduct via Buchwald-Hartwig/C-H bond functionalization reactions has been reported. This sequence offers an interesting approach for synthesizing a wide range of pyrido[1,2-a]pyrazine-3,6-dione scaffolds under mild reaction conditions in moderate to excellent yields. The scope and limitations of the protocol are discussed.

Development and synthesis of a novel salen-type ligand based on phenylalanine for Mizoroki-Heck, and S-arylation cross-coupling reactions.

In this article, we introduced a novel salen-type ligand precursor and applied it in the Pd-catalyzed Mizoroki-Heck and Cu-catalyzed S-arylation cross-coupling reactions. For the preparation of this structure, (DL)-phenyl alanine was employed as a starting material. These ligand precursor and related catalytic system can be readily synthesised. Various aryl halides (-I, -Br) and alkenes were applied successfully in this protocol to give the corresponding Mizoroki-Heck cross-coupling and S-arylated products in high to excellent yields.

Hydrodynamic volume of trehalose and its water uptake mechanism.

Trehalose ability to preserve water in biology has spawned research on this special disaccharide and its solutions. Trehalose unlike any other disaccharide, tend to mix with almost any amount of water. In water, Trehalose forms a hydrodynamic volume with bound waters (both coordination water and semicircular heterogeneities), capable of perturbing the very nature of normal bulk water. Switching of the two major conformational forms, defined by their helicities (i, i-H2O with lower helicity and ii, ii-H2O with higher helicity), were closely examined, using DFT/B3LYP- 6-311 + G** level of theory, along with molecular dynamic (MD) calculations in aqueous media. Patterns in radial distribution functions (RDF) confirmed semicircular heterogeneities, including spines of water (rows of slow water molecules), in Trehalose hydration shell. Dynamics of Trehalose conformational switch and its coordination water are coupled to dynamics of these spines of water, which are themselves coupled to dynamics of the rest of Trehalose hydration shell waters. Like seamless cogwheels such energy cascade links the upstream slow dynamics of spines to the downstream collective bulk water dynamics. This lubricates Trehalose conformational switch through coordination water uptake, for which we proposed a mechanism here. We show how the coupling between Trehalose and bound waters in its hydrodynamic volume encompass both function and dynamic of the molecule and its hydration shell. Further simulations are needed to see how this ability is related to the evading and percolating nature of cryoprotectant water, also reported for the self-coordinating jelly behavior of biological water.