THE DIMETHYLMALEOYL GROUP AS AMINO PROTECTIVE GROUP - APPLICATION TO THE SYNTHESIS OF GLUCOSAMINE-CONTAINING OLIGOSACCHARIDES

Glucosamine was readily transformed into N-dimethylmaleoyl (DMM) prote cted derivative 1 which furnished trichloroacetimidate 4 as glycosyl d onor. Reaction with various accepters (5a-g) in the presence of TMSOTf as the catalyst afforded the corresponding beta-glycosides 6a-g gener ally in high yields. Cleavage of the DMM group was readily accomplishe d by treatment with aqueous NaOH and then with HCl (pH 5). Starting fr om 1 also DMM group containing glycosyl accepters 9 and 14a-c were syn thesized. They furnished with trichloroacetimidates 12 and 4 as glycos yl donors beta(1-4)- and beta(1-3)-linked disaccharides 13 and 15a-c, respectively. From 18 as galactosyl donor and 14a as acceptor beta(1-3 )-linked disaccharide 19 was obtained in high yield, which is a versat ile building block for the important Gal beta(1-3)GlcNAc unit. 19 was transformed into trichloroacetimidate 21; glycosylation with 5e as acc eptor gave trisaccharide 22 which furnished on partial deprotection Ga l beta(1-3)GlcNAc beta(1-4)Glc derivative 24. Thus, the wide applicabi lity of DMM as amino protective group in oligosaccharide synthesis is exhibited.