Regioselective Enzyme-Mediated Glycosylation of Natural Polyhydroxy Compounds. Part 1. Galactosylation of stevioside and steviolbioside

✍ Scribed by Bruno Danieli; Monica Luisetti; Manfred Schubert-Zsilavecz; Werner Likussar; Sabine Steurer; Sergio Riva; Daniela Monti; Josef Reiner

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: German
• Weight: 478 KB
• Volume: 80
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19970800412

✦ Synopsis

Bovine ~-1,4-galactosyltransferase is an efficient catalyst for the regioselective transfer of galactose from UPD-galactose, generated in situ with the UDP-glucose/UDP-glucose-4-epimerase system, to the kaurane glycosides stevioside (1) and steviolbioside (Z), affording the corresponding galactosyl derivatives 3 and 4 in high yields. By a combination of 2 D NMR techniques (COSY, TOCSY, ROESY, HMQC, and HMBC), the structure of the products is established as -galactopyranosyl-(l -+ 4)-~-~-glucopyranosyI-(1 + 2)-fi-o-glucopyranosyl)oxy]kaur-16-en-19-oic acid P-D-ghCOpyranOSyl ester (3) and 13-[(~-~-gaIactopyranosyl-(l + 4)-P-~-glucopyranosyl-(1 + 2)-~-o-glucopyranosyl)oxy]kaur-16-en-19-~~~ acid (4).