Ganesh M. Shelke

Biochemistry and genetics of ACC deaminase: a weapon to “stress ethylene” produced in plants

1-aminocyclopropane-1-carboxylate deaminase (ACCD), a pyridoxal phosphate-dependent enzyme, is widespread in diverse bacterial and fungal species. Owing to ACCD activity, certain plant associated bacteria help plant to grow under biotic and abiotic stresses by decreasing the level of “stress ethylene” which is inhibitory to plant growth. ACCD breaks down ACC, an immediate precursor of ethylene, to ammonia and α-ketobutyrate, which can be further metabolized by bacteria for their growth. ACC deaminase is an inducible enzyme whose synthesis is induced in the presence of its substrate ACC. This enzyme encoded by gene AcdS is under tight regulation and regulated differentially under different environmental conditions. Regulatory elements of gene AcdS are comprised of the regulatory gene encoding LRP protein and other regulatory elements which are activated differentially under aerobic and anaerobic conditions. The role of some additional regulatory genes such as AcdB or LysR may also be required for expression of AcdS. Phylogenetic analysis of AcdS has revealed that distribution of this gene among different bacteria might have resulted from vertical gene transfer with occasional horizontal gene transfer (HGT). Application of bacterial AcdS gene has been extended by developing transgenic plants with ACCD gene which showed increased tolerance to biotic and abiotic stresses in plants. Moreover, distribution of ACCD gene or its homologs in a wide range of species belonging to all three domains indicate an alternative role of ACCD in the physiology of an organism. Therefore, this review is an attempt to explore current knowledge of bacterial ACC deaminase mediated physiological effects in plants, mode of enzyme action, genetics, distribution among different species, ecological role of ACCD and, future research avenues to develop transgenic plants expressing foreign AcdS gene to cope with biotic and abiotic stressors. Systemic identification of regulatory circuits would be highly valuable to express the gene under diverse environmental conditions.

A simple and efficient synthesis of 2,3-diarylnaphthofurans using sequential hydroarylation/Heck oxyarylation.

An efficient and simple strategy has been developed for the synthesis of 2,3-diarylnaphthofurans using sequential hydroarylation of naphthols and alkynes in the presence of In(OTf)3 under microwave irradiation followed by one-pot Heck-oxyarylation of generated 1-substituted-α-hydroxy styrenes.

Access to Substituted Dihydrothiopyrano[2,3-b]indoles via Sequential Rearrangements During S-Alkylation and Au-Catalyzed Hydroarylation on Indoline-2-thiones.

An efficient methodology for the synthesis of indole-fused dihydrothiopyrans has been developed from indoline-2-thiones. The protocol involves the synthesis of conjugated ene-yne-substituted indole-sulfides, a gold(III)-catalyzed rearrangement of the ene-yne side chain followed by intramolecular hydroarylation via C3-H functionalization of the indole core. This new synthesis of functionalized tricyclic indole derivatives through sequential rearrangements is quite general in nature.

Selective Synthesis of Bis(indolyl)methanes Under Solvent Free Condition Using Glucopyranosylamine Derived cis-Dioxo Mo(VI) Complex as an Efficient Catalyst

Abstractcis-Dioxomolybdenum(VI) complex of 4,6-O-ethylidene-β-d-glucopyranosylamine derived ligand has been used as an efficient catalyst in the selective synthesis of a series of bis(indolyl)methanes (BIMs) by condensing indole derivatives with carbonyl compounds. The adopted synthetic procedure is green in nature as solvent free reactions have been carried out using naturally occurring d-glucose derived ligands. Total 15 BIMs have been synthesised including four new ones, which have been characterized by mp, FTIR, NMR and mass spectroscopy. The catalyst has afforded good to excellent yield of BIMs in short reaction time and the former has been recycled five times without any significant loss in it’s catalytic efficiency.Graphical Abstract

Synthesis of 3-alkenylated indole and bis(indol-3-yl) derivatives catalyzed by sulfonic acid-functionalized ionic liquid under ultrasound irradiation

ABSTRACT A simple and efficient protocol has been developed for the synthesis of 3-alkenylated indoles and bis(indol-3-yl) derivatives by sulfonic acid-functionalized ionic liquid-catalyzed reaction of indole with 1,3-diketones/3-ketoesters under solvent-free ultrasound irradiation. Good to excellent yields (68–94%) are obtained in ultrasonication. The product of reaction is dependent on the substituent at C-2 position of indole. The catalyst is reusable and recyclable up to four cycles without significant loss of its catalytic activity. Compared with conventional heating, sound wave activation has the considerable advantages such as shorter reaction time, easy work-up, higher yields, and mild conditions. GRAPHICAL ABSTRACT