ABSTRACT
An investigation into the sensitivity of reaction conditions to a highly utilized protocol has been reported, wherein the mono-Boc functionalization of prolinol could be controlled for the exclusive synthesis of either N-Boc, O-Boc, or oxazolidinone derivatives. Mechanistic investigation revealed that the elementary steps could possibly be controlled by (a) a requisite base to recognize the differently acidic sites (NH and OH) for the formation of the conjugate base, which reacts with the electrophile, and (b) the difference in nucleophilicity of the conjugate basic sites. Herein, a successful chemoselective functionalization of the nucleophilic sites of prolinol by employing a suitable base is reported. This has been achieved by exploiting the relative acidity difference of NH and OH along with the reversed nucleophilicity of the corresponding conjugate bases N- and O-. This protocol has also been used for the synthesis of several O-functionalized prolinol derived organocatalysts, few of which have been newly reported.
ABSTRACT
Herein, organocatalytically achieved polarity reversal of cationic bromine is presented. The proven bromocation source N-bromosuccinimide (NBS) was converted to a superior bromoanion reagent by H/Br exchange with a secondary amine, substantiated with spectroscopic and computational evidence. The concept has further been used in a successfully accelerated organocatalyzed dibromination of olefins in a non-hazardous, commercially viable process with a wide range of substrate scope. The reactivity of key entities observed through NMR kinetics and reaction acceleration using only 10â mol % of catalyst account for its major success. The nucleophilicity of the bromoanion was found to be superior in comparison to other nucleophiles such as MeOH and H2 O also the protocol dominates over the competing allylic bromination reaction.
ABSTRACT
Enterobacter ludwigii is an oral growing bacteria responsible for teeth blackening. It can form biofilm. The exopolysaccharide (EPS) cluster associated with biofilm formation was isolated using ethanol precipitation and the formaldehyde-sodium hydroxide method. The chemical characterization of EPS was done using UV spectroscopy, Fourier transforms infrared spectroscopy, and gas chromatography-mass spectrometry. Energy-dispersive X-ray spectroscopy (EDS) analysis of EPS has revealed the presence of carbon > boron > nitrogen > phosphorous > calcium > sulfur > iron > potassium > magnesium. The carbon content was quite high (72.72-77.63%) in the EPS due to polysaccharide composition. The study showed the presence of different monosaccharides glucose (16.91%), galactose (4.25%), mannose (4.04%), and xylose (8.06%) as the major components of EPS. It appears such as thin filaments with three-dimensional structure, compact, irregular lumps and stacked flakes of polysaccharides. The EPS was also examined using different 1D, 2D Nuclear Magnetic Resonance (NMR) spectroscopy techniques (1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC) with different deuterated solvents (Protic and aprotic solvents for exchangeable protons), which showed eight distinguished monomers (seven confirmed by HSQC spectrum and one from 1H spectrum). Semi-crystalline nature and thermal stability were confirmed by X-ray diffractogram and differential scanning calorimetry analysis, respectively. The EPS further shows antioxidant potential in a concentration-dependent manner. It can form a stable emulsion against different edible oil that makes it promising alternative for use in food, and pharmaceutical industries. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03279-z.
