Prakash T. Parvatkar

Recent developments in the synthesis of five- and six-membered heterocycles using molecular iodine

Heterocyclic scaffolds represent the key structural subunits of many biologically active compounds. Over the last few years iodine-mediated reactions have been extensively studied due to their low cost and eco-friendliness. This Review covers advances in the field of iodine-mediated synthesis of heterocyclic compounds since 2006, especially with an emphasis on mechanisms of ring formation. In this article, syntheses of different heterocycles are classified based on the manipulation of functional groups.

An expeditious I2-catalyzed entry into 6H-indolo[2,3-b]quinoline system of cryptotackieine.

A synthesis of a series of novel 6H-indolo[2,3-b]quinolines with different substituents on the quinoline ring is described. The method involves reaction of indole-3-carboxyaldehyde with aryl amines in the presence of a catalytic amount of iodine in refluxing diphenyl ether to yield indolo[2,3-b]quinolines in one-pot. The present approach provides a new route for the synthesis of polycyclic structures related to an alkaloid cryptotackieine (neocryptolepine).

Isolation, Biological Activities and Synthesis of Indoloquinoline Alkaloids: Cryptolepine, Isocryptolepine and Neocryptolepine

The tetracyclic heteroaromatic compounds cryptolepine, isocryptolepine and neocryptolepine are all naturally occurring indoloquinoline alkaloids isolated from the shrub Cryptolepis sanguinolenta and are important due to their wide spectrum of biological properties. This review describes the isolation, brief biological activities and various synthetic methodologies developed during recent years for the preparation of this important class of alkaloids, with special emphasis on preparation and properties of cryptolepine 1, isocryptolepine 2 and neocryptolepine 3.

Next Generation Biofilm Inhibitors for Pseudomonas aeruginosa: Synthesis and Rational Design Approaches

The bacterial biofilms and the emergence of multiple drug resistance have become a major threat for current medical treatment of nosocomial infections. It has been estimated that about 65-80% of microbial infections in the developed countries are associated with biofilms. Given the prominence of biofilms in infectious diseases, increasing efforts toward the development of small molecules that will modulate bacterial biofilm development and maintenance is on the rise. Till date, marine natural products have shown a tremendous potential as pharma leads and also given new skeletons which would be used as biofilm/QS inhibitors. Medically relevant biofilm forming bacteria such as Pseudomonas aeruginosa which is most frequently isolated bacteria in nosocomial infection is believed to be a model organism for biofilm studies. Hence, in this review, we have highlighted the development of small molecules that inhibit and/or disperse bacterial biofilms of P. aeruginosa in particular. Additionally, the rational design approaches as well as synthetic methodologies along with biological studies has been accounted in this article.

Iodine catalyzed one-pot synthesis of chloro-substituted linear and angular indoloquinolines and in vitro antiproliferative activity study of different indoloquinolines

This article describes a facile one-pot synthesis of different chloro-substituted linear and angular indoloquinolines using iodine as a catalyst and in vitro antiproliferative activity of these chloro-substituted indoloquinolines (3e and 3f) and some indolo[2,3-b]quinolines (3a–d) against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells. Anti-proliferative assay against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells indicated methyl-substituted 6H-indolo[2,3-b]quinoline 3c to be the most active and the parent 6H-indolo[2,3-b]quinoline 3a to be the least active, while the other compounds including the different chloro derivatives exhibited only intermediate activity.

Recent Developments towards the Synthesis of Varitriol: an Antitumour Agent from Marine Derived Fungus Emericella variecolor

Marine natural product is recognized as a fruitful source of drug development due to their rare structural entities and diverse biological activities, and consequently, publicized number of metabolites as new medicines. Although extensive progress has been made in identifying novel bioactive molecules from marine source, great endeavor are still needed to explore these molecules for medicinal applications. Marine fungi are one of the important source of natural products, exhibiting a wide range of biological activities. (+)-Varitriol, isolated from the marine fungus Emericella variecolor, has shown 100-fold increased potency over the mean toxicity towards variety of cancer cell lines. Hence (+)-varitriol, an antitumour marine natural product has been a fascinating target for total synthesis over the last decade. The intense search for developing new approaches coupled with its biological activity has resulted in a wealth of methods towards the synthesis of this molecule. But, unfortunately only limited analogues have been synthesized and evaluated for their biological activities. Thus, there are still demands to modify aromatic part as well as sugar moiety of varitriol, which could provide the opportunity for further SAR studies to discover potential lead anticancer agents. This review describes the different strategies developed for the synthesis of varitriol and its analogues in various laboratories around the world covering literature from 2002 till date. The construction of challenging fashionable furanoside ring as well as substituted styrene derivatives are crucial steps in most of the reported synthetic endeavors.