Single-Component Globular Systems Capable of Plastic or Elastic Deformation and Structural Transitions

Elastic and plastic bending, as well as temperature-induced reversible and irreversible structural transformations, are revealed in single-molecule bicyclic phosphates. These bending properties are rare for globular systems. Structure–property analyses by single-crystal X-ray diffraction and calculations rationalize the observed behaviors. Collectively, this work identifies this class of molecules as promising candidates for flexible ferroelectric materials

Single-Component Globular Systems Capable of Plastic or Elastic Deformation and Structural Transitions

Elastic and plastic bending, as well as temperature-induced reversible and irreversible structural transformations, are revealed in single-molecule bicyclic phosphates. These bending properties are rare for globular systems. Structure–property analyses by single-crystal X-ray diffraction and calculations rationalize the observed behaviors. Collectively, this work identifies this class of molecules as promising candidates for flexible ferroelectric materials

Interstrand Cross-Links Generated by Abasic Sites in Duplex DNA

Abasic sites which are generated by hydrolysis of the glycosidic bonds connecting the heterocyclic nucleobases to the deoxyribose backbone represent the most common form of damage suffered by genomic DNA. Interestingly, an early report suggested that abasic sites can generate interstrand cross-links in duplex DNA, but the structure of these lesions has remained uncertain. The widespread occurrence of abasic sites in cellular DNA, along with the potent biological activities associated with cross-links, make it important to characterize interstrand cross-links derived from abasic sites in duplex DNA. Here, the results of gel electrophoretic and nanospray mass spectroscopic analyses of various DNA duplexes containing a single abasic site provide evidence that the aldehyde group of the DNA abasic site generates an interstrand cross-link via imine formation with the exocyclic N2-amino group of a guanine residue on the opposing strand in 5‘-d(CAp) sequences (where Ap is an abasic site)

Ferroelectricity and Uniaxial Negative Thermal Expansion in a Purely Organic Multifunctional Material

The coexistence of ferroelectricity and negative thermal expansion (NTE) in a material is rare and has yet to be observed in a purely organic single-component system. Here, we report the bifunctional characteristics of 2-(4-(trifluoromethyl)­phenyl)-1H-phenanthro [9,10-d] imidazole, a single-component system, exhibiting uniaxial ferroelectricity and anisotropic NTE properties in its various crystal forms. This purely organic material exists in trimorphic and hydrated forms. While one of the two polar forms retains its ferroelectric phase up to ∼497 K, the other exhibits a reversible large NTE below room temperature (RT), and a third centric form divests these properties. Further, the noncentric hydrated form also experiences NTE below RT. The mechanisms of ferroelectricity and NTE in this material are elucidated based on the analyses of their single-crystal X-ray structures. The interconversion of the trimorphs is demonstrated via thermal analyses. The experimental value of the in-crystal spontaneous polarization (4.6 μC/cm2) agrees well with that estimated from the periodic theoretical calculations. Given its promising figures of merit for ferroelectricity including a low coercive field (5.8 kV/cm), unusual thermal behavior, switching from NTE to positive thermal expansion, and a minimal volumetric change, this lightweight material is expected to find potential applications in nonexpansive organic electronics

Ferroelectricity and Uniaxial Negative Thermal Expansion in a Purely Organic Multifunctional Material

The coexistence of ferroelectricity and negative thermal expansion (NTE) in a material is rare and has yet to be observed in a purely organic single-component system. Here, we report the bifunctional characteristics of 2-(4-(trifluoromethyl)­phenyl)-1H-phenanthro [9,10-d] imidazole, a single-component system, exhibiting uniaxial ferroelectricity and anisotropic NTE properties in its various crystal forms. This purely organic material exists in trimorphic and hydrated forms. While one of the two polar forms retains its ferroelectric phase up to ∼497 K, the other exhibits a reversible large NTE below room temperature (RT), and a third centric form divests these properties. Further, the noncentric hydrated form also experiences NTE below RT. The mechanisms of ferroelectricity and NTE in this material are elucidated based on the analyses of their single-crystal X-ray structures. The interconversion of the trimorphs is demonstrated via thermal analyses. The experimental value of the in-crystal spontaneous polarization (4.6 μC/cm2) agrees well with that estimated from the periodic theoretical calculations. Given its promising figures of merit for ferroelectricity including a low coercive field (5.8 kV/cm), unusual thermal behavior, switching from NTE to positive thermal expansion, and a minimal volumetric change, this lightweight material is expected to find potential applications in nonexpansive organic electronics

One-Pot Cascade Annulation-Triggered Synthesis of N‑6-Substituted Norcryptotackieine Alkaloids and Evaluation of Their Antileishmanial Activities

Norcryptotackieine or 6H-indolo­[2,3-b]­quinoline is an indoloquinoline class of alkaloid isolated from Cryptolepis sanguinolenta that is traditionally used for antimalarial therapy. Additional structural tuning can extend the therapeutic potency of these indoloquinolines as antileishmanial drug leads. Synthesis of N-6-functionalized norcryptotackieines suffers from the necessity of complex pre-synthesized starting materials, restricted scope of functionalization, or tedious processes. Consequently, a straightforward synthetic procedure for accessing non-natural N-6-functionalized 6H-indolo­[2,3-b]­quinolines with potent antileishmanial activities is highly sought-after. Herein, we report a two-step one-pot synthesis of N-6-functionalized norcryptotackieine through a Pd-catalyzed double annulation reaction of commercially available amphipathic amines, 2-iodobenzyl cyanide, and differently functionalized 2-bromobenzaldehydes. The reported procedure allows a broad flexibility of substitution at the N-6 position and access to diversified scaffolds, including two natural products norcryptotackieine and neocryptolepine. Interestingly, 6d showed potent antileishmanial activities by causing disruption in the cytoskeletal structure and apoptotic-mediated death of parasites. Together, our work manifests the shortest route to N-6-substituted norcryptotackieine-derived antileishmanial agents

Accessing Benzimidazoles via a Ring Distortion Strategy: An Oxone Mediated Tandem Reaction of 2‑Aminobenzylamines

An exceptional oxone mediated tandem transformation of 2-aminobenzylamines to 2-substituted benzimidazoles is reported. It occurs at room temperature with aromatic, heteroaromatic, and aliphatic aldehydes. In this reaction initial condensation of 2-aminobenzylamine with appropriate aldehydes afforded a tetrahydro­quinazoline intermediate which underwent oxone-mediated ring distortion to afford the desired compounds in moderate to excellent yields

DNA Damage by Fasicularin

Fasicularin is a structurally novel thiocyanate-containing alkaloid isolated from the ascidian Nephteis fasicularis. Early biological experiments suggested that this compound's cytotoxic properties may stem from its ability to damage cellular DNA. Sequence gel analysis reveals that treatment of a 5‘-32P-labeled DNA duplex with fasicularin in pH 7.0 buffer causes strand cleavage selectively at guanine residues. Further experiments indicate that production of these base-labile lesions in DNA involves alkylation of guanine residues by a fasicularin-derived aziridinium ion. This work reveals fasicularin as the first natural product found to generate a DNA-alkylating aziridinium ion via a mechanism analogous to the clinically used anticancer drugs mechlorethamine, melphalan, and chlorambucil

Targeting aloe active compounds to <i>c-KIT</i> promoter G-quadruplex and comparative study of their anti proliferative property

Small molecules targeting G-quadruplex of oncogene promoter is considered as a promising anticancer therapeutics approach. Natural aloe compounds aloe emodin, and its glycoside derivative aloe emodin-8-glucoside and aloin have anticancer activity and also have potential DNA binding ability. These three compounds have promising binding ability towards quadruplex structures particularly c-KIT G-quadruplex. Here, this study demonstrates complete biophysical study of these compounds to c-KIT quadruplex structure. Aloe emodin showed highest binding stabilization with c-KIT which has been proved by absorbance, fluorescence, dye displacement, ITC and SPR studies. Moreover, comparative study of these compounds with HCT 116 cells line also agreed to their anti proliferative property which may be helpful to establish these aloe compounds as potential anticancer drugs. This study comprises a complete biophysical study along with their anti proliferative property and demonstrates aloe emodin as a potent c-KIT binding molecule. Communicated by Ramaswamy H. Sarma</p