Highly stereoselective synthesis of α,β-linked, nonreducing disaccharides related to tunicamycin

✍ Scribed by Wojciech Karpiesiuk; Anna Banaszek

• Book ID: 102997621
• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 860 KB
• Volume: 261
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(94)84021-0

✦ Synopsis

3,4,6-Tri-O-benzoyl-2-(benzoyloxyimino)-2-deoxy-alpha-D-arabino-++ +hexopyranosy l bromide (2) reacts with the O-protected 2-deoxy-2-phthalimido-beta-D-galactosamines 3 and 4 in the presence of silver triflate and sym-collidine at -78 degrees C, to give alpha,beta-(1-->1)-linked disaccharides 6a and 7a with an excellent selectivity. The 2-oxyimino function was stereospecifically converted into a 2-acetamido group by use of the LiBH4-Me3SiCl-THF reductive species, furnishing, after acetylation, the alpha-D-GlcNAc-(1-->1)-beta-D-GalNPhth nonsymmetrical, trehalose type disaccharides 13 and 14 related to tunicamycin (1, part A). Similarly, alpha-D-GlcNAc-(1-->1)-beta-D-GlcNPhth (15) was prepared, starting from 2 and 5. The factors governing the stereoselectivity of the glycosylation reactions were determined.