title: Combinatorial synthesis of deoxyhexasaccharides related to the landomycin A sugar moiety, based on an orthogonal deprotection strategy.
abstract: In this report, we describe the stereoselective synthesis of a combinatorial library comprised of 16 deoxyhexasaccharides that are related to a landomycin A sugar moiety, based on an orthogonal deprotection strategy. The use of an olivosyl donor containing a benzyl ether at the C3 position and benzoyl ester at the C4 position, and the olivosyl donor, a naphthylmethyl ether, and a p-nitrobenzylethyl or benzyl sulfonyl ester enabled the synthesis of a set of four diolivosyl units containing a hydroxyl group at the C3 or C4 position by a simple glycosylation and deprotection procedure. Using a phenylthio 2,3,6-trideoxyglycoside, alpha-selective glycosidation proceeded without anomerization of the 2,6-dideoxy-beta-glycosides. In addition, alkylhydroquinone and levulinoyl groups were found to be an effective set of orthogonal protecting groups for the anomeric position and a hydroxyl group. The coupling of all combinations of trisaccharide units in a beta-selective manner was accomplished by activation of the glycosyl imidate with I(2) and Et(3)SiH. No cleavage of the acid-labile 2,3,6-trideoxyglycoside was observed under the conditions used for the reactions. Finally, all of the protected hexasaccharides were deprotected by hydrolysis of the esters, microwave (MW) assisted cleavage of the 2-trimethylsilylethoxymethoxy (SEM) ether, and a Birch reduction.
authors.affiliation: Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-S1-35 Ookayama, Meguro, Tokyo 152-8552, Japan. thiroshi@apc.titech.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
authors.forename: Sho
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yoshizawa
authors.forename: Motoki
authors.initials: M
authors.lastname: Takagi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shin-ya
authors.forename: Takashi
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000617:Aminoglycosides / Q000138:chemical synthesis*; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000737:chemistry; D020650:Combinatorial Chemistry Techniques / Q000379:methods; D006027:Glycosides / Q000737:chemistry; D006031:Glycosylation; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D006027:Glycosides; D009844:Oligosaccharides; C064648:landomycin A