Convergent stereoselective synthesis of multiple sulfated GlcNα(1,4)GlcAβ(1,4) dodecasaccharides

In this paper, we describe an effective method for the elongation of a GlcN alpha(1,4)GlcA beta(1,4) sequence using a GlcNTroc alpha(1,4)GlcA disaccharide unit and the synthesis of the N- and/or O-sulfated GlcN alpha(1,4)GlcA beta(1,4) oligosaccharides. N-Troc protection of GlcN alpha(1,4)GlcA units was effective for the synthesis of the GlcN alpha(1,4)GlcA beta(1,4) oligosaccharides in comparison with the azido substituent. The GlcN alpha(1,4)GlcA beta( 1,4) dodecasaccharide was successfully prepared by the direct beta-selective glycosidation of glucuronate in the GlcN alpha(1,4)GlcA beta(1,4)GlcN alpha(1,4)GlcA beta(1,4) tetrasaccharide. In addition, the synthesis of the N- and/or O-sulfated GlcN alpha(1,4)GlcA beta(1,4) oligosaccharides was accomplished by fluorous-assisted deprotection and sulfation. The fluorous-assisted synthetic technology applied to the highly polar sulfated oligosaccharide permits it to be more easily separated from the highly polar reagents, such as SO3 center dot NEt3.