Selective syntheses using cyclodextrins as catalysts.

Proteases as catalysts for enzymic syntheses of opioid peptides.

Two alternative pathways leading to protease-mediated syntheses of Leu- and Met-enkephalin are described. Each peptide bond of the opiate peptides was formed by either papain, or alpha-chymotrypsin catalysis. N alpha-t-Butyloxycarbonyl amino acids and peptides or their esters served as carboxyl components, whereas amino acid and peptide phenylhydrazides were used as acceptor nucleophiles. After...

Chiral Aminophosphines as Catalysts for Enantioselective Double-Michael Indoline Syntheses

The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines c...

Bulky diarylammonium arenesulfonates as selective esterification catalysts.

More environmentally benign alternatives to current chemical processes, especially large-scale, fundamental reactions such as ester condensations, are highly desirable for many reactions. Bulky diarylammonium pentafluorobenzenesulfonates and tosylates serve as extremely active dehydration catalysts for the ester condensation reaction of carboxylic acids with equimolar amounts of sterically dema...

Cyclodextrins used as excipients

Cyclodextrins as catalysts for the removal of cholesterol from macrophage foam cells.

Low concentrations of cyclodextrins (< 1.0 mM) added to serum act catalytically, accelerating the exchange of cholesterol between cells and lipoproteins. J774 macrophages incubated with serum and 2-hydroxypropyl-beta-cyclodextrin (< or = 1 mM) released fivefold more labeled cholesterol than with serum alone. Increased efflux was not accompanied by a change in cell cholesterol mass; thus, cyclod...