Synthetic α,β-(1→4)-Glucan oligosaccharides as models for heparan sulfate. Part II

Article abstract of DOI:10.1080/07328309608005439

α,β-(1→4)-Glucan oligosaccharides were prepared as models for heparan sulfate with the simplifying assumptions that carboxyl-reduction and sulfation of heparan sulfate does not decrease the SMC antiproliferative activity and that N-sulfates in glucosamines can be replaced by O-sulfates. The target saccharides were synthesized using maltosyl building blocks. Glycosylation of methyl 2,3,6-tri-O-benzyl-α-D-glucopyranoside (1) with hepta-O-acetyl-α-maltosyl bromide (2) furnished trisaccharide 3 which was deprotected to α-D-Glc-(1→4)-β-D-Glc-(1→4)-α-D-Glc(1→OCH ₃) (5) or, alternatively, converted to the trisaccharide glycosyl acceptor (8) with one free hydroxyl function (4″-OH). Further silver triflate mediated glycosylation with glucosyl or maltosyl bromide followed by deblocking gave the tetrasaccharide β-D-Glc-(1→4)-α-D-Glc-(1→4)-β-D-Glc-(1→4)- α-D-Glc-(1→OCH₃) (11) and the pentasaccharide [α-D-Glc-(1→4)-β-D-Glc-(1→4)] ₂-α-D-Glc-(1→KDCH₃) (14). The trisaccharides 3, 4, 6, and 8 as well as pentasaccharide 12 were fully characterized by ¹H, 3, 8 and 12 also by ¹³C NMR spectroscopy Assignments were possible using 1D TOCSY, in some cases supplemented by 2D T-ROESY, ¹H,¹H 2D COSY, and ¹H-detected one-bond and multiple-bond ¹H,¹³C 2D COSY experiments.