Design and Synthesis of Dimeric Heparinoid Mimetics

Abstract

Synthetic oligosaccharide constructs exhibiting tailored and well-defined heparan sulfate (HS) like sequences offer the potential to modulate dynamic HS-dependent biomolecular recognition processes. We report an efficient strategy for the generation of HS-like fragments [GlcA-beta-(1,4)-GlcNAc] and related dimerized (gemini) disaccharides (4a and 4b) via n-pentenyl glycoside formation. When a convergent synthetic approach was utilized, construction of target molecules was achieved through a combination of chemoselective protection/deprotection protocols, imidate and n-pentenyl glycosylations, and functional group manipulations followed by ozonolysis and reductive amination. For example, glycosylation of a 2-azido glycoside (25) with a trichloroacetimidate glucuronic acid donor (13), using a catalytic amount of TMSOTf, furnished heparin-like disaccharides (28a and 28b) that were equipped with an n-pentenyl tether at the anomeric end. In turn, heparinoid-like gemini disaccharides (4a and 4b) were produced by selective transformation of the olefinic unit in the n-pentenyl glycoside to the four-carbon aldehyde followed by reductive amination with ethylenediamine. The described synthetic approach provides access to structural variants of small heparinoid oligomers as versatile building blocks for generating novel HS mimetic pharmacotherapeutics, diagnostic reagents, and biomaterials.