Block Copolymer Self-assembly: Exploitation of Hydrogen Bonding for Nanoparticle Morphology Control via Incorporation of Triazine Based Comonomers by RAFT Polymerization.

Synthesis of polymeric nanoparticles of controlled non-spherical morphology is of profound interest for a wide variety of potential applications. Self-assembly of amphiphilic diblock copolymers is an attractive bottom-up approach to prepare such nanoparticles. In the present work, RAFT polymerization is employed to synthesize a variety of poly(N,N-dimethylacrylamide)-b-poly[butyl acrylate-stat-GCB] copolymers, where GCB represents vinyl monomer containing triazine based Janus guanine-cytosine nucleobase motifs featuring multiple hydrogen bonding arrays.

Discovery of SARS-CoV-2 Inhibitors Featuring Novel Histidine α-Nitrile Motif.

As COVID-19 infection caused severe public health concerns recently, the development of novel antivirals has become the need of the hour. Main protease (M ) has been an attractive target for antiviral drugs since it plays a vital role in polyprotein processing and virus maturation. Herein we report the discovery of a novel class of inhibitors against the SARS-CoV-2, bearing histidine α-nitrile motif embedded on a simple dipeptide framework.

Carbamate-Protected (BOC and -NB) 2-Aminopyrimidinedione-Based Janus G-C Nucleobase Motifs as Building Blocks for Supramolecular Assembly and Smart Polymers.

In this paper, we report "carbamate protected" 2-aminopyrimidinedione-based Janus G-C nucleobases (2-APD Janus G-C nucleobases) featuring polymerizable groups and self-complementary triple H-bonding motifs DDA and AAD as building blocks for developing smart polymers and self-healing materials. The carbamate-masked H-bonding motif, cleavable under acidic (BOC group) or photocleavable (-nitrobenzyl group) conditions, would facilitate the synthesis of smart polymers by alleviating aggregation during polymerization which in turn would exclude self-assembly-assisted solubility issues. Ready accessibility in excellent yields coupled with the possibility for facile introduction of polymerizable groups would make these building blocks excellent candidates for diverse polymerization applications.

2-Amino-5-methylene-pyrimidine-4,6-dione-based Janus G-C nucleobase as a versatile building block for self-assembly.

This communication reports a nature-inspired Janus G-C nucleobase featuring two recognition sites: DDA (G mimic) and DAA (C mimic), which is capable of forming a linear tape-like supramolecular polymer structure. As demonstrated herein, the amino group of this self-assembling system can be further modified to yield a highly stable quadruple H-bonding system as well as a masked self-assembling system cleavable upon exposure to light.

Histidinal-Based Potent Antimalarial Agents.

Herein we report the synthesis and evaluation of peptide-histidinal conjugated drug scaffolds, which have the potential to target the hemoglobin-degrading proteases falcipain-2/3 from the human malaria parasite. Scaffolds with various substitutions were tested for antimalarial activity, and compounds 8 g, 8 h, and 15 exhibited EC50 values of ∼0.018 μM, ∼0.

Janus Cross-links in Supramolecular Networks.

Thermosets composed of cross-linked polymers demonstrate enhanced thermal, solvent, chemical, and dimensional stability as compared to their non-cross-linked counterparts. However, these often-desirable material properties typically come at the expense of reprocessability, recyclability, and healability. One solution to this challenge comes from the construction of polymers that are reversibly cross-linked.

Three in One: Triple G-C-T Base-Coded Brahma Nucleobase Amino Acid: Synthesis, Peptide Formation, and Structural Features.

This note reports the synthesis and peptide formation of a novel triple G-C-T nucleobase amino acid (NBA) building block featuring three recognition faces: DDA (G mimic), DAA (C mimic), and ADA (T mimic). Readily obtainable in multigram scale in a remarkably easy one-step reaction, this unique NBA building block offers scope for wide ranging applications for nucleic acid recognition and nucleic acid peptide/protein interaction studies.

Triazine-Based Janus G-C Nucleobase as a Building Block for Self-Assembly, Peptide Nucleic Acids, and Smart Polymers.

This communication reports on the utility of a triazine-based self-assembling system, reminiscent of a Janus G-C nucleobase, as a building block for developing (1) supramolecular polymers, (2) peptide nucleic acids (PNAs), and (3) smart polymers. The strategically positioned self-complementary triple H-bonding arrays DDA and AAD facilitate efficient self-assembly, leading to a linear supramolecular polymer.

Novel cilengitide-based cyclic RGD peptides as αvβ integrin inhibitors.

In this letter, we report a series of five new RGD-containing cyclic peptides as potent inhibitors to αvβ integrin protein. We have incorporated various unnatural lipophilic amino acids into the cyclic RGD framework of cilengitide, which is selective for αvβ integrin. All the newly synthesized cyclic peptides were evaluated in vitrosolid phase binding assay and investigated for their bindingbehaviourtowards integrin subtypes.

Correction: Conducting nanofibres of solvatofluorochromic cyclohexanetrione-dithiolylidene-based C symmetric molecule.

Correction for 'Conducting nanofibres of solvatofluorochromic cyclohexanetrione-dithiolylidene-based C3 symmetric molecule' by Kilingaru I. Shivakumar et al., Chem.

Twelve-Armed Hexaphenylbenzene-Based Giant Supramolecular Framework for Entrapping Guest Molecules.

Host-guest chemistry is a functional model in supramolecular chemistry for understanding specific process occurring in biological systems. Herein, we describe a rationally designed giant multiarmed hexaphenylbenzene (HPB)-based supramolecular frameworks which encapsulate a variety of guest molecules in the voids of their crystal lattice through the cooperative interplay of multivalency, noncovalent forces and backbone rigidity. In this connection, pseudo-axially substituted twelve-armed hexaphenylbenzene was synthesized and its molecular entrapping nature was studied by varying number of H-bond donor-acceptor sites in the arms.

Conducting nanofibres of solvatofluorochromic cyclohexanetrione-dithiolylidene-based C symmetric molecule.

We report a novel set of easily tailorable C symmetric molecules with a π-extended core and adorned with different thioalkyl groups, exhibiting solvatofluorochromic and amphoteric redox behaviour. The nearly planar core exhibits intermolecular face-to-face π-stacking, SS and intramolecular SO interactions. Current-sensing atomic force microscopy studies revealed a high conductivity of ∼0.

A modular approach towards functionalized highly stable self-complementary quadruple hydrogen bonded systems.

Self-complementary quadruple hydrogen bonded systems have shown potential as key building blocks for developing various supramolecular polymers. Opportunities for the introduction of multiple functionalities would further augment, in principle, their application potential. Herein, we report a novel modular approach to simultaneously introduce two closely aligned side chains into AADD-type self-complementary quadruple hydrogen-bonding systems.

Mixed-Stack Charge Transfer Crystals of Pillar[5]quinone and Tetrathiafulvalene Exhibiting Ferroelectric Features.

Ferroelectric materials find extensive applications in the fabrication of compact memory devices and ultra-sensitive multifunctional detectors. Face-to-face alternate stacking of electron donors and acceptors effectuate long-range unidirectional ordering of charge-transfer (CT) dipoles, promising tunable ferroelectricity. Herein we report a new TTF-quinone system-an emerald green CT complex consisting pillar[5]quinone (P5Q) and tetrathiafulvalene (TTF).

Coumarin-Appended Stable Fluorescent Self-Complementary Quadruple-Hydrogen-Bonded Molecular Duplexes.

In this paper we report a coumarin-conjugated self-assembling system adorned with valuable features such as high duplex stability and a built-in fluorophore, which would augment its application potential. This system forms a highly stable molecular duplex in a nonpolar solvent (K > 1.9 × 10 M in CDCl).

Three in one: prototropy-free highly stable AADD-type self-complementary quadruple hydrogen-bonded molecular duplexes with a built-in fluorophore.

This communication reports an effective approach for addressing the prototropy-related problems in heterocycle-based AADD-type self-assembling systems by freezing their hydrogen-bonding codes, by utilizing intramolecular bifurcated hydrogen bonding interactions. Using this strategy, we have also developed a hydroquinone-conjugated AADD-type self-assembling system adorned with three valuable features such as prototropy-free dimerization yielding single duplexes, high duplex stability and a built-in fluorophore, which would augment its application potential. The rational approach used herein to arrest prototropic shift may also find application elsewhere, wherein proton shift-mediated structural changes become a detrimental factor.

Triazine-Based Highly Stable AADD-Type Self-Complementary Quadruple Hydrogen-Bonded Systems Devoid of Prototropy.

A new class of 1,3,5-triazine-based quadruple hydrogen-bonded system featuring AADD-type self-complementary arrays has been developed and characterized. This system forms highly stable molecular duplex in non-polar solvent (K >1.9×10  m in CDCl ) without prototropy-related issues, raising its prospects for application in supramolecular polymer science.

Self-assembled vesicles of urea-tethered foldamers as hydrophobic drug carriers.

Molecular self-assembly of nonamphiphilic α,β-hybrid foldamers based on urea-tethered anthranilic acid-proline (Ant-Pro) foldamers is reported. These self-assembled hollow vesicular architectures can take up and release the anticancer hydrophobic drug curcumin.

Angiotensin II analogs comprised of Pro-Amb (γ-turn scaffold) as angiotensin II type 2 (AT(2)) receptor agonists.

We describe herein the design, synthesis and conformational investigation of Pro-Amb (proline-3-amino-2-methoxybenzoic acid) incorporated Angiotensin II and its truncated analogues. Solution-state NMR and CD studies suggest γ-turn-like conformation in Pro-Amb analogs in aqueous solution. Furthermore, Pro-Amb analogs have been shown to act as AT2 receptor agonists.

Novel hybrid nocodazole analogues as tubulin polymerization inhibitors and their antiproliferative activity.

We describe the design, synthesis and SAR profiling of a series of novel combretastatin-nocodazole conjugates as potential anticancer agents. The thiophene ring in the nocodazole moiety was replaced by a substituted phenyl ring from the combretastatin moiety to design novel hybrid analogues. The hydroxyl group at the ortho position in compounds 2, 3 and 4 was used as the conformationally locking tool by anticipated six-membered hydrogen bonding.

Reversal of H-bonding direction by N-sulfonation in a synthetic reverse-turn peptide motif.

This communication depicts an intriguing example of hydrogen-bonding reversal upon introduction of a sulfonamide linkage at the N-terminus of a synthetic reverse-turn peptide motif. The ready availability of two sulfonyl oxygen atoms, as hydrogen-bonding acceptors, combined with the inherent twisted conformation of sulfonamides are seen to act as switches that engage/disengage the hydrogen-bond at the sticky ends/termini.

Conformational modulation of peptides using β-amino benzenesulfonic acid ((S)Ant).

This communication describes the utility of a conformationally restricted aromatic β-amino acid (2-aminobenzenesulfonic acid, (S)Ant) inducing various folding interactions in short peptides. Sandwiching (S)Ant between diverse amino acid residues was shown to form robust folded architectures featuring a variety of H-bonded networks, suggesting its utility in inducing peptide folding.

Synthetic turn mimetics and hairpin nucleators: Quo Vadimus?

Structural mimicry of peptides has witnessed perceptible progress in the last three decades. Reverse turn and β-hairpin units are the smallest secondary structural motifs that are some of the most scrutinized functional cores of peptides and proteins. The practice of mimicking, without altering the function of the bioactive core, ranges from conformational locking of the basic skeleton to total replacement of structural architecture using synthetic analogues.

Conformational modulation of peptide secondary structures using β-aminobenzenesulfonic acid.

This communication describes the influence of β-aminobenzenesulfonic acid ((S)Ant) on the conformational preferences of hetero foldamers. The designed (Aib-(S)Ant-Aib)n and (Aib-(S)Ant-Pro)n oligomers display a well-defined folded conformation featuring intramolecular mixed hydrogen bonding (7/11) and intra-residual (6/5) H-bonding interactions, respectively.