Morindone, an Anthraquinone, Intercalates DNA Sans Toxicity: a Spectroscopic and Molecular Modeling Perspective

For the first time, interaction between non-toxic anthraquinone morindone with both natural and synthetic DNA duplexes has been demonstrated in this paper. Detailed analyses of the binding of morindone with DNA via UV?Cvis, FTIR, and circular dichroism spectroscopies were carried out. In addition, bioinformatics tools have been employed to scrutinize the binding of the dye with DNA in silico. Results represent morindone to be a better binder with a score of ?5.79 compared to EtBr (known mutagenic intercalator) recorded at ?5.02. Further interaction is accentuated by the microscope-assisted evidence of nuclear specific staining of tissues by morindone. The electrophoretic analysis reveals the efficacy endowed within morindone dye in rendering protection to DNA exposed to H₂O₂ damage and thereby conferring it safe to the nucleic acid. As DNA is often the target for majority of anticancer and antibiotic drugs, study on the interaction between molecules like morindone and DNA has relevance and implications in several biological applications including cancer therapy. Thus, we propose that morindone can also be harnessed as a diagnostic probe for DNA structure in addition to DNA-directed therapeutics.     

Light‐Triggered Capture and Release of DNA and Proteins by Host–Guest Binding and Electrostatic Interaction

The development of an effective and general delivery method that can be applied to a large variety of structurally diverse biomolecules remains a bottleneck in modern drug therapy. Herein, we present a supramolecular system for the dynamic trapping and light‐stimulated release of both DNA and proteins. Self‐assembled ternary complexes act as nanoscale carriers, comprising vesicles of amphiphilic cyclodextrin, the target biomolecules and linker molecules with an azobenzene unit and a charged functionality. The non‐covalent linker binds to the cyclodextrin by host–guest complexation with the azobenzene. Proteins or DNA are then bound to the functionalized vesicles through multivalent electrostatic attraction. The photoresponse of the host–guest complex allows a light‐induced switch from the multivalent state that can bind the biomolecules to the low‐affinity state of the free linker, thereby providing external control over the cargo release. The major advantage of this delivery approach is the wide variety of targets that can be addressed by multivalent electrostatic interaction, which we demonstrate on four types of DNA and six different proteins.     

Enantioselective Michael addition of aldehydes to nitroolefins catalyzed by pyrrolidine-HOBt

The oxytriazole catalyst “pyrrolidine-HOBt” developed for asymmetric Michael addition of cyclohexanone to nitroolefins is now evaluated for the asymmetric Michael addition of aldehydes to nitroolefins under similar reaction conditions. The results of this study indicate that, the oxytriazole catalyst “pyrrolidine-HOBt” is equally effective in promoting the Michael addition of aldehydes to nitroolefins on employing benzoic acid as an additive. The desired products, γ-nitrocarbonyl compounds were obtained in good yields and high enantioselectivities.     

1,3,5‐Triaza‐7‐phosphaadamantane (PTA) Derived Caged Phosphines for Palladium‐Catalyzed Selective Functionalization of Nucleosides and Heteroarenes

Phosphines have, in combination with transition metals, played a pivotal role in the rapid development of efficient catalytic processes. Caged phosphines constitute a class of three‐dimensional scaffolds providing unique control over steric and electronic properties. The versatility of the caged phosphine ligands has been demonstrated elegantly by the groups of Verkade, Gonzalvi as well as Stradiotto. Our research group has also been working extensively for the past several years in the development of 1,3,5‐triaza‐7‐phosphaadamantane‐based caged ligands and in this personal note we have summarized these applications pertaining to the modification of biologically useful nucleosides and heteroarenes.     

Efforts towards the synthesis of microsporin B: ready access to both the enantiomers of the key amino acid fragment

Both the isomers methyl-(2S,8R)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate and methyl-(2S,8S)-2-((tert-butoxycarbonyl)amino)-8-hydroxydecanoate of an unusual amino acid residue and the key fragment of microsporin B are prepared. The key steps include cross metathesis and enzymatic kinetic resolution. In addition, a linear tetrapeptide with desired components towards total synthesis is also reported.     

A short and efficient synthesis of honokiol via Claisen rearrangement

A concise and efficient total synthesis of honokiol, a biphenyl-type neolignan is accomplished in six steps using readily available and cost-effective reagents. The synthetic route involves mainly the Grignard reaction, iodine mediated aromatization, and Claisen rearrangement as key steps. A predominant formation of honokiol (1a) was observed in the Claisen rearrangement under microwave irradiation whereas the isohonokiol (1b) was formed as a major product under conventional conditions.