title: Application of lipase-catalyzed regioselective esterification in the preparation of digitonin derivatives.
abstract: The oligosaccharide chain of the monodesmosidic haemolytic saponin digitonin (1) undergoes an efficient and regioselective acylation in organic solvent by use of Novozym 435 (lipase B from Candida antarctica supported on acrylic resin) in the presence of an activated ester. With vinyl acetate, acetylation occurs at C-6 OH of glucose(II) and C-4 OH of xylose to afford the previously unreported diacetyl derivative 2 and the monoacetyl derivatives 3 and 4. With vinyl laurate only the monolauryl derivative 5 is formed. The structures of these acylated digitonins have been established using modern 2D NMR techniques, which allowed complete assignments of all proton resonances. The hemolytic activity of derivatives 2-5 is significantly reduced compared to that of digitonin.
authors.affiliation: Dipartimento di Chimica Organica e Industriale, Università degli Studi di Milano, Centro CNR di Studio per le Sostanze Organiche Naturali, via Venezian 21, 20133 Milano, Italy. danieli@icil64.cilea.it
authors.forename: B
authors.initials: B
authors.lastname: Danieli
authors.forename: M
authors.initials: M
authors.lastname: Luisetti
authors.forename: S
authors.initials: S
authors.lastname: Steurer
authors.forename: A
authors.initials: A
authors.lastname: Michelitsch
authors.forename: W
authors.initials: W
authors.lastname: Likussar
authors.forename: S
authors.initials: S
authors.lastname: Riva
authors.forename: J
authors.initials: J
authors.lastname: Reiner
authors.forename: M
authors.initials: M
authors.lastname: Schubert-Zsilavecz
mesh_terms: D000818:Animals; D002175:Candida / Q000201:enzymology; D002240:Carbohydrate Sequence; D002417:Cattle; D004072:Digitonin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000494:pharmacology; D004952:Esters; D006461:Hemolysis; D066298:In Vitro Techniques; D008049:Lipase; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data
chemical_list: D004952:Esters; D008049:Lipase; D004072:Digitonin