2,5-Diamide-Substituted Five-Membered Heterocycles: Challenging Molecular Synthons

Renewable Polyurethanes from Sustainable Biological Precursors

Due to the depletion of fossil fuels, higher oil prices, and greenhouse gas emissions, the scientific community has been conducting an ongoing search for viable renewable alternatives to petroleum-based products, with the anticipation of increased adaptation in the coming years. New academic and industrial developments have encouraged the utilization of renewable resources for the development of ecofriendly and sustainable materials, and here, we focus on those advances that impact polyurethane (PU) materials. Vegetable oils, algae oils, and polysaccharides are included among the major renewable resources that have supported the development of sustainable PU precursors to date. Renewable feedstocks such as algae have the benefit of requiring only sunshine, carbon dioxide, and trace minerals to generate a sustainable biomass source, offering an improved carbon footprint to lessen environmental impacts. Incorporation of renewable content into commercially viable polymer materials, particularly PUs, has increasing and realistic potential. Biobased polyols can currently be purchased, and the potential to expand into new monomers offers exciting possibilities for new product development. This Review highlights the latest developments in PU chemistry from renewable raw materials, as well as the various biological precursors being employed in the synthesis of thermoset and thermoplastic PUs. We also provide an overview of literature reports that focus on biobased polyols and isocyanates, the two major precursors to PUs.

Methyl Scanning for Mechanochemical Chalcogen-Bonding Cascade Switches

Chalcogen-bonding cascade switching was introduced recently to produce the chemistry tools needed to image physical forces in biological systems. In the original flipper probe, one methyl group appeared to possibly interfere with the cascade switch. In this report, this questionable methyl group is replaced by a hydrogen. The deletion of this methyl group in planarizable push-pull probes was not trivial because it required the synthesis of dithienothiophenes with four different substituents on the four available carbons. The mechanosensitivity of the resulting demethylated flipper probe was nearly identical to that of the original. Thus methyl groups in the switching region are irrelevant for function, whereas those in the twisting region are essential. This result supports the chalcogen-bonding cascade switching concept and, most importantly, removes significant synthetic demands from future probe development.

Halogen and Chalcogen Bond Energies Evaluated Using Electron Density Properties

Halogen (X-bond) and chalcogen bond (Ch-bond) energies for 36 complexes have been obtained at the RI-MP2/def2-TZVP level of theory, involving the heavier halogen and chalcogen atoms (Br, I, Se, Te). We have explored the existence of linear relationships between the interaction energies and the local kinetic energy densities at the bond critical points that characterize the σ-hole interactions (both electronic G(r) and potential V(r) energy densities). Interestingly, we have found strong relationships for halogen and chalcogen bonding energies, especially for the V(r) energy density, thus allowing to estimate the interaction energy without computing the separate monomers. This is also useful to estimate the interaction in monomeric systems (intramolecular X/Ch-bonds), as illustrated using several examples. Remarkably, we have also found a good relationship when in the same representation both halogen and chalcogen atoms are included, thus allowing to use the same empirical correlation for both interactions.

A Chalcogen-Bonding Cascade Switch for Planarizable Push-Pull Probes

Planarizable push-pull probes have been introduced to demonstrate physical forces in biology. However, the donors and acceptors needed to polarize mechanically planarized probes are incompatible with their twisted resting state. The objective of this study was to overcome this "flipper dilemma" with chalcogen-bonding cascade switches that turn on donors and acceptors only in response to mechanical planarization of the probe. This concept is explored by molecular dynamics simulations as well as chemical double-mutant cycle analysis. Cascade switched flipper probes turn out to excel with chemical stability, red shifts adding up to high significance, and focused mechanosensitivity. Most important, however, is the introduction of a new, general and fundamental concept that operates with non-trivial supramolecular chemistry, solves an important practical problem and opens a wide chemical space.

Crystal structure of diethyl 2-amino-5-{4-[bis-(4-methyl-phen-yl)amino]-benzamido}-thio-phene-3,4-di-carboxyl-ate

In the title compound, C31H31N3O5S, the regioselective substitution of the thio-phene is confirmed with the amine and the amide at the 2- and 5-positions, respectively. In the mol-ecule, the thio-phene ring is twisted by 12.82 (3)° with respect to the aromatic ring of the benzamido group. Intra-molecular N-H⋯O hydrogen bonds are present involving the N atoms of the primary amine and the amide groups, forming S(6) ring motifs. In the crystal, centrosymmetrically related mol-ecules are linked by pairs of N-H⋯O hydrogen bonds involving the amide carbonyl O atoms and the primary amine N atoms to form dimers of R 2 2(16) ring motif.

Lynamicin D an antimicrobial natural product affects splicing by inducing the expression of SR protein kinase 1

The first total synthesis of the antimicrobial natural product lynamicin D has been developed using a Suzuki coupling to construct the bisindole pyrrole skeleton. An evaluation of the biological activity of lynamicin D reveals that it has a minor effect on cell viability but it can modulate splicing of pre-mRNAs. We provide evidence that this effect is mainly due to the ability of lynamicin D to alter the levels of SRPK1, the key kinase involved in both constitutive and alternative splicing.

Application of Ynamides in the Synthesis of 2-(Tosylamido)- and 2,5-Bis(tosylamido)thiophenes

A step-economic and metal-catalyst-free synthesis of 2-(tosylamido)- and 2,5-bis(tosylamido)-thiophenes from nonsymmetrical 1,3-butadiynamides and symmetrical 1,3-butadiyne-1,4-diamides is reported. The reaction proceeds in the presence of Na2S·9H2O (2-3 equiv) under mild reaction conditions (50 °C) and is facilitated by polarized carbon-carbon triple bonds in ynamides. This new approach to thiophenes based on the chemistry of ynamides was applied to the synthesis of a bis(tosylamido)-capped terthiophene having a string of N,S-heteroatoms embedded in a highly π-conjugated molecular frame.