Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and ...

We have identified a novel tRNA methyltransferase in Saccharomyces cerevisiae that we designate Trm9. This enzyme, the product of the YML014w gene, catalyzes the esterification of modified uridine nucleotides, resulting in the formation of 5-methylcarbonylmethyluridine in tRNA(Arg3) and 5-methylcarbonylmethyl-2-thiouridine in tRNA(Glu). In intact yeast cells, disruption of the TRM9 gene results...

In the course of light adaptation in the retina, the visual pigment, rhodopsin, which is located in the visual cell outer segment, releases vitamin A aldehyde (2, 3). The aldehyde is then enzymatically reduced to vitamin A (3) by reduced triphosphopyridine nucleotide (4) in the outer segment. The vitamin A is subsequently converted to vitamin A ester by the particulate matter of retinal tissue ...

alpha-Chymotrypsin exhibits photoswitchable activities in an organic solvent after covalent modification of the protein backbone with thiophenefulgide active ester (2). The thiophenefulgide-modified alpha-chymotrypsin exhibits reversible photoisomerizable properties between states (3)-E and (3)-C. The modified alpha-chymotrypsin, where nine lysine residues are substituted by thiophenefulgide un...

Esterifications of carboxylic acids with equimolar amount of alcohols could be efficiently catalyzed by ZrOCl(2) x 8H(2)O. Acrylate esters were obtained in good yields under solvent-free conditions at ambient temperature. The esterification of other carboxylic acids with alcohols also proceeded at ambient temperature or at 50 oC to afford esters in high yields. If the esterification was perform...

Sugar fatty acid esters are practical importance and have a variety of applications that include surfactants and as an emulsifying agent. In this study, we report glucose stearate synthesis using lipase-Fe3O4 nanoparticles catalyst. The influence of various reaction factors, such as silica gel concentration, molar ratio of sugar/acid, reaction temperature and speed of agitation on esterificatio...

The bimolecular reaction of carboxylic acids with diazoalkanes to form esters is among the mildest and most efficient of organic transformations but is seldom used in synthesis beyond the important case of methyl esterification. This is largely a consequence of the inaccessibility and poor stability of higher diazoalkanes as substrates. In this work we describe a new method for the synthesis of...

barium salts of dibenzylidene cystines 8a-c were obtained from the reaction of lcystine with benzaldehyde or its derivatives in the presence of barium hydroxide. their reduction with zinc and hydrochloric acid in methanol yielded the narylmethylcysteines ?9a-c?. these can, in turn, be converted by esterification into the methyl esters ?10 a-c. ?reaction of n, n'-carbonyl diimidazole (im co...

The methyl, ethyl, propyl and butyl esters of the fatty acids of Thevetia peruviana seed oil were successfully prepared by the batch-esterification procedures. Various acid catalyst and various molar ratios of fatty acid to alcohol were investigated. H3PO4 was found to be ineffective to catalyze the esterification of the free fatty acid. HCl gas and conc. H2SO4 both proved very effective in cat...

Based on starch and series of alkyl benzene sulfonic acid as the materials, a novel carbon-based solid acid catalyst is synthesized using hydrothermal method. This catalyst exhibits much higher catalytic activity in the reaction of esterification of Mono-fatty alcohol polyoxyethylene maleate esters with 1,4-butanediol. The structure of carbon-based solid acid catalyst was charactered by IR and ...