Indole: A Privileged Heterocyclic Moiety in the Management of Cancer

Salicylaldehyde-Cobalt(II)-Catalyzed C-H Alkoxylation of Indoles with Secondary Alcohols

A straight and efficient protocol for the synthesis of hindered indole-ethers via C-H alkoxylation of indoles was developed by a cobalt-catalyzed cross-dehydrogenative coupling reaction with secondary alcohols. The selection of the salicylaldehyde-Co(II) catalyst enables the reaction to proceed under conditions without acid or base addition in the presence of limited alcohols. The protocol has broad substrate scope for both indole and secondary alcohols and exhibits good functional tolerance. The synthetic applications are proven by gram-scale reaction and further diversification of the product. Preliminary mechanistic investigations indicate that the activation of C-H bonds is not the rate-determining step of the reaction.

Synthesis and Anticancer Evaluation of Novel Indole Based Arylsulfonylhydrazides against Human Breast Cancer Cells

A series of novel indole based sulfonohydrazide derivatives (5a-k) containing morpholine heterocyclic ring were synthesized through multistep chemical reactions. The target compounds (5a-k) were prepared by the reaction of substituted phenyl sulfonylhydrazides (2a-k) with morpholine derivative of indole 3-carboxaldehyde. All the target compounds were screened for their anticancer activity in vitro against the estrogen receptor-positive breast cancer line MCF-7 and triple-negative breast cancer cell line, MDA-MB-468. It was found that among all the evaluated compounds, the chemotype 4-chloro-N'-((1-(2-morpholinoethyl)-1H-indol-3-yl)methylene)benzenesulfonohydrazide (5f) showed promising inhibition of both MCF-7 and MDA-MB-468 cancer cells with the respective IC₅₀ values of 13.2 μM and 8.2 μM. Compound 5f was found to be nontoxic against HEK 293 noncancerous cells in the studied concentration range, therefore indicating that such chemotypes inhibit the proliferation of cancerous cells selectively and significantly.

Enantioselective Propargylation of Oxonium Ylide with α-Propargylic-3-Indolymethanol: Access to Chiral Propargylic Indoles

An enantioselective three-component reaction of α-propargylic-3-indolymethanol with diazoindolinone and alcohol under cocatalysis of Rh(II) and chiral phosphoric acid (CPA) has been reported. It proceeds through the regio- and enantiospecific addition of the in situ formed oxonium ylide to the α-propargylic indole iminium ion that is generated from 3-indolyl propargylic alcohol with CPA. This work features an asymmetric counteranion-directed propargylation of oxonium ylide, and provides an efficient access to chiral propargylic indole derivatives with high yields and enantioselectivities.

Access to Polycyclic Indole-3,4-Fused Nine-Membered Ring via Cascade 1,6-Hydride Transfer/Cyclization

A cascade aldimine condensation/1,6-hydride transfer/Mannich-type cyclization of indole-derived phenylenediamine with aldehydes was developed for one-step construction of a polycyclic indole-3,4-fused skeleton. Aldehyde serves as a key to start the whole process, including 1,6-hydride transfer enabled δ-C(sp³)-H activation of the secondary amine. The challenges of construction of medium-sized rings are addressed via hydride transfer chemistry.

Crystal structure and Hirshfeld analysis of diethyl (2E,2'E)-3,3'-[1-(8-phenyl-isoquinolin-1-yl)-1H-indole-2,7-di-yl]diacrylate

In the mol­ecule of title compound, intra­molecular π–π inter­actions between the indole unit and benzene ring help to establish the clip-shaped conformation of the mol­ecule. In the crystal, the mol­ecules are assembled into two-dimensional layers via C—H⋯O hydrogen bonds, π–π and C—H⋯π inter­actions.

The mol­ecule of title compound, C₃₃H₂₈N₂O₄, comprises an indole unit (A), an iso­quinoline moiety (B) and a benzene ring (C). The dihedral angles between these groups are A/B = 57.47 (1), A/C = 18.48 (1) and B/C = 57.97 (1) °. The ethyl acrylate group at the 2-position is nearly co-planar with the indole unit [3.81 (2)°], while that at the 7-position is distinctly non-coplanar [52.64 (1)°]. Intra­molecular π–π inter­actions between the indole unit and benzene ring help to establish the clip-shaped conformation of the mol­ecule. In the crystal, the mol­ecules are assembled into two-dimensional layers via C—H⋯O hydrogen bonds, π–π and C—H⋯π inter­actions. Hirshfeld surface analysis illustrates that the greatest contributions are from H⋯H (63.2%), C⋯H/H⋯C (15.4%) and O⋯H/H⋯O (14.8%) contacts. The terminal C₂H₅ group of one of the ethyl acrylate side chains is disordered over two positions of equal occupancy.

Recent developments in mitogen activated protein kinase inhibitors as potential anticancer agents

The mitogen activated protein kinase (MAPK) belongs to group of kinase that links the extracellular stimuli to intracellular response. The MAPK signalling pathway (RAS-RAF-MEK-ERK) involved in different pathological conditions like cancer, caused due to genetic or any other factor such as physical or environmental. Many studies have been conducted on the pathological view of MAPK cascade and its associated element like RAS, RAF, MEK, ERK or its isoforms, and still the research is going on particularly with respect to its activation, regulation and inhibition. The MAPK signalling pathway has become the area of research to identify new target for the management of cancer. A number of heterocyclics are key to fight with the cancer associated with these enzymes thus give some hope in the management of cancer by inhibiting MAPK cascade. In the present article, we have focussed on MAPK signalling pathway and role of different heterocyclic scaffolds bearing nitrogen, sulphur and oxygen and about their potential to block MAPK signalling pathway. The heterocyclics are gaining importance due to high potency and selectivity with less off-target effects against different targets involved in the MAPK signalling pathway. We have tried to cover recent advancements in the MAPK signalling pathway inhibitors with an aim to get better understanding of the mechanism of action of the compounds. Several compounds in the preclinical and clinical studies have been thoroughly dealt with. In addition to the synthetic compounds, a significant number of natural products containing heterocyclic moieties as MAPK signalling pathway inhibitors have been put together. The structure activity relationship along with docking studies have been discussed to apprehend the mechanistic studies of various compounds that will ultimately help to design and develop more MAPK signalling pathway inhibitors.