Addition of ester enolates to N-alkyl-2-fluoropyridinium salts: total synthesis of (+/-)-20-deoxycamptothecin and (+)-camptothecin

Anticancer Therapeutic Effects of Green Tea Catechins (GTCs) When Integrated with Antioxidant Natural Components

After decades of research and development concerning cancer treatment, cancer is still at large and very much a threat to the global human population. Cancer remedies have been sought from all possible directions, including chemicals, irradiation, nanomaterials, natural compounds, and the like. In this current review, we surveyed the milestones achieved by green tea catechins and what has been accomplished in cancer therapy. Specifically, we have assessed the synergistic anticarcinogenic effects when green tea catechins (GTCs) are combined with other antioxidant-rich natural compounds. Living in an age of inadequacies, combinatorial approaches are gaining momentum, and GTCs have progressed much, yet there are insufficiencies that can be improvised when combined with natural antioxidant compounds. This review highlights that there are not many reports in this specific area and encourages and recommends research attention in this direction. The antioxidant/prooxidant mechanisms of GTCs have also been highlighted. The current scenario and the future of such combinatorial approaches have been addressed, and the lacunae in this aspect have been discussed.

A spotlight on alkaloid nanoformulations for the treatment of lung cancer

Numerous naturally available phytochemicals have potential anti-cancer activities due to their vast structural diversity. Alkaloids have been extensively used in cancer treatment, especially lung cancers, among the plant-based compounds. However, their utilization is limited by their poor solubility, low bioavailability, and inadequacies such as lack of specificity to cancer cells and indiscriminate distribution in the tissues. Incorporating the alkaloids into nanoformulations can overcome the said limitations paving the way for effective delivery of the alkaloids to the site of action in sufficient concentrations, which is crucial in tumor targeting. Our review attempts to assess whether alkaloid nanoformulation can be an effective tool in lung cancer therapy. The mechanism of action of each alkaloid having potential is explored in great detail in the review. In general, Alkaloids suppress oncogenesis by modulating several signaling pathways involved in multiplication, cell cycle, and metastasis, making them significant component of many clinical anti-cancerous agents. The review also explores the future prospects of alkaloid nanoformulation in lung cancer. So, in conclusion, alkaloid based nanoformulation will emerge as a potential gamechanger in treating lung cancer in the near future.

Reassembly and functionalization of N-CF3 pyridinium salts: synthesis of nicotinaldehydes

An unprecedented hydrolyzation-triggered ring opening and recyclization cascade to construct biologically interesting nicotinaldehydes.

Cu(I)-Catalyzed Oxygen and Nitrogen Nucleophiles Triggered Regioselective Synthesis of Furo/Pyrrolo-Annulated Quinolines

Cu(I)-catalyzed intramolecular annulation of o-ethynylquinoline-3-carbaldehydes leads to the synthesis of alkoxy/imidazole-substituted 1,3-dihydrofuro[3,4-b]quinolines via C-O and C-N bond formation. The scope of the reaction was further extended to o-ethynylquinoline-3-carbonitriles for the synthesis of alkoxy-substituted 3H-pyrrolo[3,4-b]quinolines using alcohols as nucleophiles. These reactions are regioselectively favoring the 5-exo-dig cyclizations in all the annulation processes.

Synthesis of N-alkylated 2-pyridones through Pummerer type reactions of activated sulfoxides and 2-fluoropyridine derivatives

N-Alkylated 2-pyridone products were obtained in good to excellent yields through a one-pot procedure involving either normal or interrupted Pummerer reactions between triflic anhydride activated sulfoxides and 2-fluoropyridine derivatives, followed by hydrolysis. This is a rare case that uses 2-fluoropyridine as a nucleophile in Pummerer type reactions.

Anticancer Activity of Natural Compounds from Plant and Marine Environment

This paper describes the substances of plant and marine origin that have anticancer properties. The chemical structure of the molecules of these substances, their properties, mechanisms of action, their structure⁻activity relationships, along with their anticancer properties and their potential as chemotherapeutic drugs are discussed in this paper. This paper presents natural substances from plants, animals, and their aquatic environments. These substances include the vinca alkaloids, mistletoe plant extracts, podophyllotoxin derivatives, taxanes, camptothecin, combretastatin, and others including geniposide, colchicine, artesunate, homoharringtonine, salvicine, ellipticine, roscovitine, maytanasin, tapsigargin, and bruceantin. Compounds (psammaplin, didemnin, dolastin, ecteinascidin, and halichondrin) isolated from the marine plants and animals such as microalgae, cyanobacteria, heterotrophic bacteria, invertebrates (e.g., sponges, tunicates, and soft corals) as well as certain other substances that have been tested on cells and experimental animals and used in human chemotherapy.

Pyridinium salts: from synthesis to reactivity and applications

This review highlights the pyridinium salts in terms of their natural occurrence, synthesis, reactivity, biological properties, and diverse applications.

Synthesis, utility and medicinal importance of 1,2- & 1,4-dihydropyridines

The present review aims to describe various methodologies that have been used for the synthesis of 1,2- & 1,4-dihydropyridines (DHPs) and also highlight their medicinal significance.

Application of the aza-Diels–Alder reaction in the synthesis of natural products

The Diels–Alder reaction that involves a nitrogen atom in the diene or dienophile is termed the aza-Diels–Alder reaction.

Total Synthesis of Camptothecin and Related Natural Products by a Flexible Strategy

A flexible strategy for constructing natural products containing indolizinone or quinolizinone scaffolds and their analogues was developed, which was based on a cascade exo hydroamination followed by spontaneous lactamization. This method was applied in the total synthesis of camptothecin in nine steps in a new ring-forming approach. It was also used to efficiently prepare five biogenetically or structurally related natural alkaloids, including 22-hydroxyacuminatine, oxypalmatine, norketoyobyrine, naucleficine, and nauclefine, as well as 35 natural-product-like molecules. We believe that this method and the small-molecule library prepared with it can open new avenues for studying the bioactivity of camptothecin and Nauclea natural products.

Alstoscholarisines H-J, Indole Alkaloids from Alstonia scholaris: Structural Evaluation and Bioinspired Synthesis of Alstoscholarisine H

Alstoscholarisines H-J (1-3), new monoterpenoid indole alkaloids with an unprecedented skeleton created via the formation of a C-3/N-1 bond, were isolated from Alstonia scholaris. Their structures were established by extensive spectroscopic analyses and the assessment of single-crystal X-ray diffraction data. The total synthesis of alstoscholarisine H was achieved via the regioselective nucleophilic addition of pyridinium through a bioinspired iminium ion intermediate followed by Pictet-Spengler-like cyclization.

Competitive intramolecular C–C vs. C–O bond coupling reactions toward C6 ring-fused 2-pyridone synthesis

This work described a competitive C–C vs. C–O bond forming reaction at the challenging C₆-position of 2-pyridones through Pd catalysis and silver radical cyclization.

Conjugated imines and iminium salts as versatile acceptors of nucleophiles

Growing interests in nitrogen-containing molecules involving bioactive and functional materials have stimulated the recent development of synthetic methodologies where nucleophilic addition reactions to imino carbons are utilized in crucial steps. This article summarizes double nucleophilic addition reactions with alpha,beta-unsaturated aldimines, addition reactions using alkynyl imines, "umpoled" reactions of alpha-imino esters, and the use of iminium salts as reactive electrophiles.

Synthesis and topoisomerase poisoning activity of A-ring and E-ring substituted luotonin A derivatives

A series of A-ring and E-ring analogues of the natural product luotonin A, a known topoisomerase I poison, was evaluated for growth inhibition in human carcinoma and leukemia cell lines. Rational design of structures was based on analogues of the related alkaloid camptothecin, which has been demonstrated to exert cytotoxic effects by the same mechanism of action. When compared to luotonin A, several compounds exhibited an improved topoisomerase I-dependent growth inhibition of a human leukemia cell line.

Novel, efficient total synthesis of natural 20(S)-camptothecin

Enantiopure 20(S)-camptothecin has been prepared from a known hydroxypyridone through a novel approach that involves a Claisen rearrangement, an asymmetric nucleophilic ethylation, a Heck coupling and a Friedländer condensation as the key transformations.

Synthesis of 14-Azacamptothecin, a Water-Soluble Topoisomerase I Poison

14-Azacamptothecin, a potent, water-soluble analogue of the antitumor agent camptothecin, has been prepared by a convergent synthesis. The key condensation of the AB and DE rings with concomitant formation of ring C of 14-aza CPT was carried out in two stages, the latter of which involved a radical cyclization strategy. [structure: see text]

Camptothecin: current perspectives

This review provides a detailed discussion of recent advances in the medicinal chemistry of camptothecin, a potent antitumor antibiotic. Two camptothecin analogues are presently approved for use in the clinic as antitumor agents and several others are in clinical trials. Camptothecin possesses a novel mechanism of action involving the inhibition of DNA relaxation by DNA topoisomerase I, and more specifically the stabilization of a covalent binary complex formed between topoisomerase I and DNA. This review summarizes the current status of studies of the mechanism of action of camptothecin, including topoisomerase I inhibition and additional cellular responses. Modern synthetic approaches to camptothecin and several of the semi-synthetic methods are also discussed. Finally, a systematic evaluation of novel and important analogues of camptothecin and their contribution to the current structure-activity profile are considered.

Combined Directed Ortho Metalation/Cross-Coupling Strategies: Synthesis of the Tetracyclic A/B/C/D Ring Core of the Antitumor Agent Camptothecin

A convergent synthesis of the A/B/C/D ring fragment 5 of camptothecin using a combination of directed ortho metalation and Negishi cross-coupling is described. The key features of the synthetic sequence are an anionic ortho-Fries rearrangement (10 --> 12), a Negishi cross-coupling (7 --> 6), and a terminal modified von Braun reaction (16 --> 5) that leads to tetracyclic derivative 5 in 7 steps and 11% overall yield.