Cholesterol esters, which can comprise over 75% of total cholesterol in diets rich in organ meats, must first be hydrolyzed by pancreatic cholesterol esterase (EC 3.1.1.13) before being absorbed (1). In its hydrolytic mode, catalysis by the enzyme involves a classical serine esterase mechanism in which the seroxide anion displaces the sterol moiety to give an acyl-enzyme intermediate, followed ...

Sulfur functions in position 8 of the flavin nucleus give rise to new modified flavin derivatives, which should prove useful as probes of the flavin binding domains of flavoproteins. Here, we report on some properties of 8-nor-8-alkylmercaptoflavins and 8-nor-8-mercaptoflavin which are readily formed by nucleophilic displacement by alkylmercaptides or sulfide, with 8-nor-8-chloroflavins as star...

N-(2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)ethyl)-6-fluoronicotinamide ([(18)F]FNEM), a novel prosthetic agent that is thiol-specific, was synthesized using a one-pot two-step strategy: (1) (18)F incorporation by a nucleophilic displacement of trimethylammonium substrate under mild conditions; (2) amidation of the resulting 6-[(18)F]fluoronicotinic acid 2,3,5,6-tetrafluorophenyl ester with N-(2...

Herein, the preparation of neoglycoconjugates bearing mannose-6-phosphate analogues is described by: (a) synthesis of a cyclic sulfate precursor to access the carbohydrate head-group by nucleophilic displacement with an appropriate nucleophile; (b) introduction of spacers on the mannose-6-phosphate analogues via Huisgen's cycloaddition, the Julia reaction, or the thiol-ene reaction under ultras...

Adenosine 5’-( thiophosphate) (AMPS) contains a prochiral phosphorus center. Differentiation of the two diastereotopic oxygens would allow elucidation of the stereochemical course of biological adenylyl transfer reactions. A general method was developed to distinguish between the “pro-R’ and “pro-S’ oxygens. When we converted the AMPS to the isomer A of adenosine S-( 1-thiotriphosphate) (ATP&),...

Employing the oxidative coupling of phenylacetylene with benzaldehyde as a model reaction, a density functional theory (DFT) study combined with extended X-ray absorption fine structure (EXAFS) experiment was carried out to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition. Newly reported DFT method M11-L computed results suggest that the mononuclear zi...