Biotransformation of 3-cyanopyridine to nicotinic acid using whole-cell nitrilase of Gordonia terrae mutant MN12

In the present study, the Gordonia terrae was subjected to chemical mutagenesis using ethyl methane sulfonate (EMS) and methyl methane sulfonate (MMS), N-methyl-N-nitro-N-nitrosoguanidine (MNNG), 5-bromouracil (5-BU) and hydroxylamine with the aim of improving the catalytic efficiency of its nitrilase for conversion of 3-cyanopyridine to nicotinic acid. A mutant MN12 generated with MNNG exhibited increase in nitrilase activity from 0.5 U/mg dcw (dry cell weight) (in the wild G. terrae) to 1.33 U/mg dcw. Further optimizations of culture conditions using response surface methodology enhanced the enzyme production to 1.2-fold. Whole-cell catalysis was adopted for bench-scale synthesis of nicotinic acid, and 100% conversion of 100 mM 3-cyanopyridine was achieved in potassium phosphate buffer (0.1 M, pH 8.0) at 40 °C in 15 min. The whole-cell nitrilase of the mutant MN12 exhibited higher rate of product formation and volumetric productivity, i.e., 24.56 g/h/g dcw and 221 g/L as compared to 8.95 g/h/g dcw and 196.8 g/L of the wild G. terrae. The recovered product was confirmed by HPLC, FTIR and NMR analysis with high purity (> 99.9%). These results indicated that the mutant MN12 of G. terrae as whole-cell nitrilase is a very promising biocatalyst for the large-scale synthesis of nicotinic acid.

Synthetic drives for useful drug molecules through organocatalytic methods

The treatment of various pathological conditions in human beings involves the use of safe and efficacious drug substances. But there are different complications associated with the treatment of various disease states including drug resistance, adverse drug reactions, toxicity, etc. To minimize these problems, there is an urgent need to develop new therapeutics with suitable pharmacokinetic and pharmacodynamic properties. So, the organocatalytic methods are emerged as a potential synthetic tool to accelerate the design of new drug candidates with improved physicochemical and pharmacological properties, selectivity, and efficiency for the treatment of life-threatening diseases. Organocatalytic reactions refer to the chemical reaction that is accelerated by organic catalysts instead of using organometallic catalysts. Organocatalysts are more advantageous in comparison to metallic catalysts because organocatalysts are cost-effective, stable, efficient, non-toxic, readily available, and easy to handle. In addition to this, the organocatalysis method involves an eco-friendly reaction by minimizing the formation of by-products and reducing the chemical hazards. Organocatalysts are categorized into four classes such as Lewis acids, Lewis bases, Bronsted acids, and Bronsted bases. These catalysts are generally involved in various reactions mechanisms such as Aldol reaction, Diels–Alder reactions, Michael Addition and Knoevenagal reactions, etc. The utility of organocatalyst in synthetic chemistry results in the development of medicinally active compounds with diverse structural features.

Methods to Produce Nicotinic Acid with Potential Industrial Applications

Nicotinic acid is a naturally occurring pyridine carboxylic acid, contained in vitamin PP, an essential nutrient for humans and animals, and used as an antipelagic agent. Nicotinic acid can be made from tryptophan by plants and animals but is usually not completely bioavailable. Industrially, nicotinic acid is produced mainly by oxidation of 5-ethyl-2-methylpyridine with nitric acid. One of the by-products of the process is nitrous oxide, a gas that is difficult to recycle and manage, with a greenhouse effect 300 times stronger than CO₂. A new technology for the industrial production of nicotinic acid is undoubtedly necessary to meet the needs of green chemistry and not burden the environment. We carried out a literature review on ecological methods to produce nicotinic acid from commercially available raw materials such as 3-methylpyridine and 5-ethyl-2-methylpyridine, especially focusing on those methods with potential industrial applications.

Type I 'Lighted Metal-free' Photosensitizing Assemblies of Phenazine for Aerobic Oxidative Transformations

Highly photostable supramolecular photosensitizing 'lighted metal-free' assemblies of DPZ-Th have been developed which show strong absorption in the visible region and excellent electron transportation potential from donor to acceptor units. The as-prepared assemblies of DPZ-Th activate aerial oxygen to generate Type I reactive oxygen species (ROS) under visible-light irradiation in mixed aqueous media. Owing to these properties, the as-prepared DPZ-Th assemblies exhibit high photocatalytic activity in catalyzing the aerobic oxidative coupling of benzylamines and synthesis of quinazolines. Various spectroscopic studies support the participation of Type I reactive species in the reaction mechanism. The 'pure' oxygen environment was not needed for carrying out these transformations and all the reactions proceed very well under aerial conditions to furnish the desired products in high yields.

Nickel-Catalyzed [4 + 2] Annulation of Nitriles and Benzylamines by C-H/N-H Activation

Nickel-catalyzed [4 + 2] annulation of benzylamines and nitriles via C-H/N-H bond activation, providing straightforward atom-economic access to a wide variety of multisubstituted quinazolines, is reported. Mechanistic investigation revealed that the in situ formed amidines from the coupling of benzylamines and nitriles direct the nickel catalyst to activate the ortho-C-H bond of the phenyl ring of the benzylamine.