Potential application of native lipases in the resolution of (RS) - phenylethylamine

Reactions of acid anhydrides—II : Reactions of ketones with mixed sulphonic-carboxylic anhydride, isopropenyl acetate, and acetic anhydride

N-(2-Hydroxyphenyl)acetamide is an intermediate for the complete natural synthesis of antimalarial drugs. Chemoselective monoacetylation of the amino group of 2-aminophenol to N-(2-hydroxyphenyl)acetamide was carried out by employing Novozym 435 as the catalyst. Different acyl donors such as vinyl acetate, vinyl butyrate, acetic anhydride, and ethyl acetate were studied. The effect of various parameters such as different acyl donors, speed of agitation, solvent, catalyst loading, mole ratio, and temperature was studied. Vinyl acetate was found to be the best acyl donor among the studied acyl donors since it leads to an irreversible reaction. It is a kinetically controlled synthesis since vinyl acetate was used as the activated acyl donor. The substrate to acyl donor ratio was 1:3. The mechanism for the given reaction system was predicted based on the observations of Lineweaver–Burk plots. It was observed that the reaction followed a ternary complex model with inhibition by vinyl acetate, and kinetic constants were estimated using the Polymath 6.0 software. Under the final optimized conditions, the conversion for the reaction was found to be 74.6% in 10 h.

Distribution of acetyl groups alters the properties of acetylated starch.

A comparative study on the acetylation of wood by reaction with vinyl acetate and acetic anhydride

Between 721.7 and 636.4 K, vinyl acetate undergoes thermal decomposition according to the rate equation log (k/s–1)= 10.43 – 182.4/2.303 RT(R= 8.312 J mol–1 K–1). Approximately 95% of reaction is decarbonylation to give acetone, with decomposition to ketene and acetaldehyde being the minor component. The latter reaction is an analogue of acetic anhydride pyrolysis which takes place at least 106 times faster per β-hydrogen at 600 K. This very large rate difference parallels that between β-keto-acids and βγ-alkenoic acids and contrasts markedly with pyrolysis of alkyl acetates and alkyl vinyl ethers, which occurs at closely similar rates. The contrasting behaviour most probably reflects differences in the principal bond-breaking step of the reaction, which for vinyl acetate and acetic anhydride (and also the acids) is breaking of the β–X–H bond so that the nucleophilicity of the attacking group assumes major importance; for esters and vinyl ethers this is not the most important step so their reaction rates are similar. The relative reactivities to the acids support an alternative view that both vinyl acetate and acetic anhydride pyrolyse via their enol forms. The greater understanding of the factors affecting gas-phase elimination rates permits prediction of the relative rates of compounds not yet studied. Pyrolysis of 1,2-diacetoxyethane gave non-first-order plots, with rate acceleration due to formation of the more reactive vinyl acetate. The β-acetoxy-group (OCOMe) increased the rate of elimination (per β-hydrogen at 600 K)ca. 7-fold, which compares with factors of 388 and 144 for COMe and CO2Me respectively, and a reduction of 3.6-fold by OMe.

In this study, the reactivity of wood components with acetic anhydride or vinyl acetate was studied. It was found that the reactivity of wood components was virgin wood flour > holocellulose >> a-cellulose. Acetylation of Turkish pine or cedar wood flour with acetic anhydride was significantly improved in the presence of potassium carbonate at 100°C. Maximum of about 20 and 18% weight percentage gain (WPG) values were obtained with Turkish pine ( Pinus brutia ) and cedar ( Cedrus libani ) wood flour after 3 h reaction at 100°C, respectively. The two modification methods and the effect of wood components on vinyl acetate (VA) or acetic anhydride (AA) modification, were characterised by infrared analysis in detail. As an apparent advantage of this new method, acetaldehyde was formed as by-product which is non-acidic was removed easily after the reaction due to low the boiling point of acetaldehyde [b.p. (760 mm Hg) = 21°C]. Key words : Acetic anhydride, vinyl acetate, holocellulose, α-cellulose, FTIR, chemical modification

A new, concise, and efficient route towards both antipodes of N‐(β‐hydroxypropyl)indoles is described. The key step is an enantioselective lipase‐mediated acetylation of racemic indolic alcohols [1‐(1H‐indol‐1‐yl)propan‐2‐ol, 1‐(2‐methyl‐1H‐indol‐1‐yl)propan‐2‐ol, and 1‐(5‐bromo‐1H‐indol‐1‐yl)propan‐2‐ol] with enol esters (vinyl acetate and isopropenyl acetate) as acyl group donors, performed under kinetically controlled conditions. A substantial influence of enzyme type, acyl group donor, and organic solvent on conversion rates and enantioselectivity of the enzymatic kinetic resolutions (EKRs) of the respective racemates was examined in detail. The best results in terms of enantioselectivity were obtained for the resolutions performed with native lipase from Pseudomonas fluorescens (PFL, Amano AK) in diisopropyl ether (DIPE) or tert‐butyl methyl ether (TBME) solution. To support the assignment of the absolute configurations of EKR products, chemical correlations with enantiomerically enriched analytical standards and single‐crystal X‐ray diffraction analysis were applied.

Chemical modifications of Scots pine (Pinus sylvestris) wood flour were performed with vinyl acetate (VA) and acetic anhydride (AA) in the presence of potassium carbonate as a catalyst. Scots pine wood flour samples were successfully acetylated with VA (19 wt% gain) and AA (24 wt% gain). The effect of chemical modification of the Scots pine wood flour with AA and VA on the mechanical properties of wood high-density polyethylene composites (WPC) was determined. It was observed that acetylation of wood flour allowed a significant increase in both the mechanical properties and the thermal stability of the WPCs. It was concluded that acetylation of lignocellulosic fibers improves thermal stability, dispersion in the polymer matrix, and compatibility with the polymer matrix.

Comparative determination of the grafting distribution and viscoelastic properties of wood blocks acetylated by vinyl acetate or acetic anhydride

Enzymatic synthesis of phenethyl ester from phenethyl alcohol with acyl donors.

In-vitro and In-silico study on the acylation reaction of (-)-isopulegol and l-menthol with lipase from Rhizomucor miehei have been done. In this study, the acylation reaction was conducted by using two kinds of acyl source, acetic anhydride and vinyl acetate. The reaction was performed at 50°C and mole ratio of (-)-isopulegol:l-menthol:acetic acid anhydride or vinyl acetate was 1:1:3. In-vitro study, shows that lipase from Rhizomucor miehei have catalyzed the acylation reaction in a good way, whereas acetic anhydride was more effectively as acyl source than vinyl acetate. The selectivity product of (-)-isopulegyl acetate and l-menthyl acetate after reaction in 24 h are 34,58% and 21,52% respectively. In-silico study gives the results which correlated with in-vitro study, in case of determination the suitable of acyl source. There are verified by the value of Kd which represent the interaction between (-)-isopulegol, l-menthol or acyl source as ligand with lipase as macromolecule. This work also gives the prediction of mechanism reaction model from in-silico study

Acetic anhydride and vinyl acetate differentially modify the supramolecular structure of starch.

Lipases from different sources and two mycelium-bound lipases, in a free or immobilized form, in ginger starch film were screened as biocatalysts in the reaction of (R,S)-1-phenylethanol (1) with vinyl acetate and other acylating agents. The effect of various reaction parameters in the resolution of (1) catalyzed by lipase from Burkholderia cepacia (BCL) immobilized in ginger starch film was evaluated (acyl donor type, alcohol:acyl donor molar ratio, temperature and organic solvent). The catalytic efficiency of BCL immobilized in polymeric blends of ginger starch and polyethylene oxide (PEO), in different compositions, was also studied. Vinyl acetate and iso-propenyl acetate furnished the highest conversion (9%) and enantiomeric excess (> 99%) of the (R)-ester. The alcohol:acyl donor molar ratio and temperature optimum were 1:1 and 28 ºC, respectively. The mixture of n-hexane/glycerol (9:1 v:v) was the most adequate for this reaction (conversion 23%, E > 200). The ginger starch/PEO (7:3 m/m) blend was successfully reused six times consecutively.

Zeolite Catalysts as Solid Solvents in Fine Chemicals Synthesis: 2. Competitive Adsorption of the Reactants and Products in the Friedel–Crafts Acetylations of Anisole and Toluene

Naringin, one of the citrus flavonoids and known as a natural antioxidant, has limited bioavailability owing to its low stability and solubility. However, naringin esters formed via acylation have recently been reported to possess improved physical and chemical properties. The development of these compounds has a great potential in the food, cosmetic and pharmaceutical industries, but low conversion and productivity are barriers to industrial applications. This study aimed to improve the conversion of naringin acetate, which is formed via the enzymatic reaction between naringin and an acyl donor. An optimal reaction condition was determined by evaluating the effect of various variables (enzyme type, enzyme concentration, acyl donor, molar ratio of reactants, reaction temperature, and solvent) on the synthesis of naringin acetate. The optimal condition was as follows: 3 g/L of Lipozyme TL IM, molar ratio of 1:5 (naringin:acyl donor), reaction temperature of 40 °C, and acetonitrile as the reaction solvent. Under this condition, the maximum conversion to naringin acetate from acetic anhydride and vinyl acetate was achieved at approximately 98.5% (8 h) and 97.5% (24 h), respectively. Compared to the previously reported values, a high conversion was achieved within a short time, confirming the commercial potential of the process.