Abstract
The desired compound (10) was synthesized from crude stachyose (1). Compound 1, separated from tubers of Stachys sieboldi MIQ., was heated with aqueous acetic acid to yield manninotriose, which was isolated as a crystalline β-undecaacetate (2). Treatment of 2 with saturated hydrogen bromide in acetic acid afforded a crystalline acetobromomanninotriose (3). Methyl glycosidation of 3 followed by deacetylation gave methyl β-manninotrioside (4) as a white powder. Selective tritylation and subsequent acetylation of 4 afforded a crystalline methyl nona-O-acetyl-6"-O-trityl-β-manninotrioside (6). Stirring of 6 with acetobromogalactose in nitromethane in the presence of silver perchlorate and Drierite yielded the acetate (9) in 42% yield. Deacetylation of 9 gave 10 as a white powder. Methylation of 10 by Hakomori's method gave a crystalline fully methyl ether (11). The structure of 10 was confirmed by GC and GC-MS analyses of acid hydrolysates of 11. β-Galactosidase from jack bean meal hydrolyzed 10 to D-galactose and methyl β-manninotrioside.
