β-Carboline directed regioselective hydroxylation by employing Cu(OAc)2 and mechanistic investigation by ESI-MS

Ru(II)-Catalyzed regioselective carbene insertion into β-carbolines and isoquinolines

A protocol for carbene insertion into the inert C(sp²)-H bond has been established wherein β-carbolines and isoquinolines are explored as intrinsic directing groups. The Ru(II)-catalyzed strategy employing sulfoxonium ylides as the carbene precursor offers an effective and atom-economical functionalization of substrates of biological interest with only DMSO as the sole by-product. The strategy is scalable to gram scale, and it also showcases a wide range of functional group tolerance. ESI-MS studies assisted in the identification of intermediates and consolidation of a probable mechanistic pathway. Furthermore, investigations revealed that the functionalized molecules not only displayed selective inhibition against cancer cell lines, but also demonstrated promising photophysical properties.

Ru(II)-Catalyzed Regioselective C-N Bond Formation on Benzothiazoles Employing Acyl Azide as an Amidating Agent

A Ru(II)-catalyzed regioselective direct ortho-amidation of 2-aryl benzo[d]thiazoles employing acyl azides as a nitrogen source has been accomplished. This approach utilizes the efficiency of benzothiazole as a directing group and the role of acyl azide as an effective amidating agent toward C-N bond formation, thereby evading the general Curtius rearrangement. The protocol highlights significant functional group tolerance, single-step, and external oxidant-free conditions, with the release of only innocuous molecular nitrogen as the byproduct. The reaction mechanism and the intermediates associated with this selective Ru-catalyzed reaction have been investigated using ESI-MS. The protocol also aided in the construction of ortho-amidated β-carbolines, unveiling another class of fluorescent molecules.

The Role of Sulphonamides and N-Sulphonyl Ketimines/Aldimines as Directing Groups in the Field of C-H Activation

Sulphonamides and N-sulphonyl ketimines/aldimines have turned out to be versatile motifs in the field of synthetic and medicinal chemistry. The field of C-H activation/functionalization flourished remarkably due to their synthetic applicability and directing group plays a remarkable role to achieve regioselectivity in these reactions. The current review summarizes recent tactics by utilizing sulphonamides and N-sulphonyl ketimines/aldimines as directing groups for C-H activation or functionalization. As a directing group, they also facilitate site selectivity and late-stage functionalization of drug molecules in order to construct complex scaffolds of therapeutic importance by C-H activation.

β-Carboline-based molecular hybrids as anticancer agents: a brief sketch

Cancer is a huge burden on the healthcare system and is foremost cause of mortality across the globe. Among various therapeutic strategies, chemotherapy plays an enormous role in overcoming the challenges of treating cancer, especially in late stage detection. However, limitations such as extreme side/adverse effects and drug resistance associated with available drugs have impelled the development of novel chemotherapeutic agents. In this regard, we have reviewed the development of β-carboline-based chemotherapeutic agents reported in last five years. The review mainly emphasizes on the molecular hybrids of β-carbolines with various pharmacophores, their synthetic strategies, and in vitro anticancer evaluation. In addition, the mechanisms of action, in silico studies, structural influence on the potency and selectivity among diverse cancer cell lines have been critically presented. The review updates readers on the diverse molecular hybrids prepared and the governing structural features of high potential molecules that can help in the future development of novel cytotoxic agents.

TCCA-mediated oxidative rearrangement of tetrahydro-β-carbolines: facile access to spirooxindoles and the total synthesis of (±)-coerulescine and (±)-horsfiline

Multi-reactive centered reagents are beneficial in chemical synthesis due to their advantage of minimal material utilization and formation of less by-products. Trichloroisocyanuric acid (TCCA), a reagent with three reactive centers, was employed in the synthesis of spirooxindoles through the oxidative rearrangement of various N-protected tetrahydro-β-carbolines. In this protocol, low equivalents of TCCA were required to access spirooxindoles (up to 99% yield) with a wide substrate scope. Furthermore, the applicability and robustness of this protocol were proven for the gram-scale total synthesis of natural alkaloids such as (±)-coerulescine (1) and (±)-horsfiline (2) in excellent yields.

Three-reactive centered reagent (TCCA) mediated construction of spirooxindoles through an oxidative rearrangement of various N-protected tetrahydro-β-carbolines and total synthesis of natural alkaloids (±)-coerulescine and (±)-horsfiline.

Recent evolution on synthesis strategies and anti-leishmanial activity of β-carboline derivatives - An update

Leishmaniasis is the most widespread pathogenic disease in several countries. Currently, no effective vaccines are available, and the control of Leishmaniasis primarily relies on decade-old chemotherapy. The treatment for the Leishmaniasis is not up to the mark. Current therapy for Leishmaniasis is ancient and requires hospitalization for the administration. These medications are also highly toxic and resistant. β-carboline, a natural indole containing alkaloid, holds a vital position in the field of medicinal chemistry with a diversified pharmacological action. The current review focuses mainly on the anti-leishmanial effects of β-carboline analogs and their synthetic strategies, structural activity relationship studies (SAR). The past ten years alterations unveiled by β-carboline analogs present in phytoconstituents and various derivatives of synthesized analogs with the mechanism of action were briefly shortlisted and illustrated.

The microwave-assisted syntheses and applications of non-fused single-nitrogen-containing heterocycles

Microwave technology has emerged as a great tool for the efficient synthesis of organic compounds and it provides opportunities for chemists to achieve chemical transformations that tend to be challenging using classical approaches. Additionally, N-heterocycles are well-known for their medicinal/biological significance, along with their applications as excellent building blocks in chemical synthesis. The dominance of N-heterocycles in drug molecules and other pharmacological agents makes them attractive scaffolds, which encourages chemists to develop a wide range of strategies towards the greener synthesis and functionalization of these heterocycles. In this regard, we have collated and discussed literature relating to the microwave-assisted synthesis and the modification of non-(benzo)fused single-nitrogen-containing N-heterocycles from the past decade. The role of the microwave technique and its benefits over the conventional approach have also been emphasized in terms of overall reaction efficiency, reaction time, yield, reduced side-product generation, neat and clean reactions, chemo-/regio-/enantio-selectivity, and the use of mild reagents/reaction conditions to achieve the objectives of green and sustainable chemistry.