Stereoselective .alpha.-glycosylation of nitro sugar evernitrose: synthesis of the terminal AB unit of everninomicin antibiotics

• Published in: Journal of organic chemistry Vol. 56; no. 25; pp. 7144 - 7149
• Main Authors: Juetten, Peter, Scharf, Hans Dieter, Raabe, Gerhard
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.12.1991; Amer Chemical Soc
• Subjects: Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides; Carbohydrates. Nucleosides and nucleotides; Chemistry; Chemistry, Organic; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Heterocyclic compounds; Organic chemistry; Organic compounds; Physical Sciences; Physics; Preparations and properties; Science & Technology; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; OLIGOSACCHARIDES; ORTHOSOMYCINS; DICHLOROISOEVERNINIC ACID; STEREOCHEMISTRY; FRAGMENT; CURAMYCIN-A; DAUNORUBICIN; Nitro compound; Aldose; Molecular structure; Halophenols; Glycosylation; Branched compound; Experimental study; X ray diffraction; Disaccharide; Chemical reduction; Stereoselectivity; Aminoglycoside; Benzenic compound; Glycoside; Organic compounds; Crystalline structure
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo00025a034

The stereoselective alpha-glycosylation of branched-chain nitro sugar evernitrose (17, 2,3,6-trideoxy-3-C-methyl-4-O-methyl-3-nitro-alpha-L-arabino-hexopyranose) is described. 1-O-p-Nitrobenzoyl derivatives 18-beta and 18-alpha were prepared as glycosyl donors starting from evernitrose 17 and its methyl glycoside 12, respectively. Glycosylation of 18 and 4-O-benzoyl-2,6-dideoxy-D-arabino-hexopyranoside 15 in CH2Cl2 in the presence of TMS triflate promoter at -78-degrees-C gave the alpha-linked disaccharide 19 exclusively. Alkaline treatment of the protected glycoside 19 led to disaccharide 20. Curacin derivative 7 and 18-alpha were coupled again by using TMS triflate in CH2Cl2 at -78-degrees-C to give crystalline alpha-linked disaccharide 23 exclusively in 73% yield. Hydrogenolytic cleavage of the phenolic benzyl ether completed the synthesis of the terminal AB unit of everninomicins 8. The structure and stereochemistry of everninonitrose methyl glycoside 8 have been tentatively deduced from the H-1 NMR spectrum and confirmed by single-crystal X-ray analysis. Reduction of 8 with Al/Hg in aqueous ethanol afforded everninosamine methyl glycoside 9, the terminal AB unit of antibiotic 13-384 component 5 (5).