A versatile approach to the synthesis of glycans containing mannuronic acid residues

Reported herein is a new method for a highly effective synthesis of beta-glycosides from mannuronic acid donors equipped with the 3-O-picoloyl group. The stereocontrol of glycosylations was achieved by means of the H-bond-mediated aglycone delivery (HAD). The method was utilized for the synthesis of a tetrasaccharide linked via beta-(1 -> 3)-mannuronic linkages. We have also investigated 3,6-lactonized glycosyl donors that provided moderate to high beta-manno stereoselectivity in glycosylations. A method to achieve complete alpha-manno stereoselectivity with mannuronic acid donors equipped with 3-O-benzoyl group is also reported.