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Synthesis 2005(11): 1783-1788  
DOI: 10.1055/s-2005-869957
PAPER
© Georg Thieme Verlag Stuttgart · New York

Preparative Route to Per-O-acetylated N-Acetyl- and N-(tert-Butoxycarbonyl)neuraminyl-α-(2→3)-galactosyl Disaccharide Glycosyl Donors by Regioselective Acetolysis of Sialyl-α-(2→3′)-lactose

Andrei A. Shermana, Olga N. Yudinaa, Bozhena S. Komarovaa, Yury E. Tsvetkova, Stefano Iacobellib, Nikolay E. Nifantiev*a
a N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prospect 47, 119991 Moscow, Russia
Fax: +7(095)1358784; e-Mail: nen@ioc.ac.ru;
b Department of Oncology and Neurosciences, Sections of Medical Oncology and Pathology, University ‘G. D’Annunzio’, Chieti 66100, Italy
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Publication History

Received 16 February 2005
Publication Date:
20 June 2005 (online)

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Abstract

Per-O-acetylated N-acetylneuraminyl-α-(2→3)-galactopyranose was prepared in three steps in good overall yield from sialyl-α-(2→3′)-lactose by regioselective cleavage of the galactosyl-β-(1→4)-glucose linkage by acetolysis and then readily converted into the corresponding disaccharide 1-trichloroacetimidate or ethyl thioglycoside, valuable synthetic blocks for the preparation of complex sialylated oligosaccharides. The N-acetyl group in the disaccharide thioglycoside was replaced by an N-Boc one via intermediate formation of a mixed N-Ac-N-Boc imide followed by chemoselective de-N-acetylation with hydrazine hydrate in DMF. An example of application of the disaccharide thioglycoside for the preparation of a spacer-armed hexasaccharide SLex is described.

Key words

carbohydrates - oligosaccharide - cleavage - acetals - glycosides - regioselectivity