Synthesis of lactoside glycodendrons using photoaddition and reductive amination methodologies

Carbohydrate-based divalent and tetravalent lactoside glycodendrons were constructed in a convergent manner. The dendrons were synthesized beginning with the photoaddition of hepta-O-acetyl-1-thio-β-lactose, in an anti-Markovnikov manner, to a bis-allyl AB₂ trisaccharide to form a divalent dendron. Following two nearly quantitative deprotection steps, the divalent lactoside was coupled to another AB₂ trisaccharide by reductive amination to afford a tetravalent dendron. These paucivalent compounds were characterized by NMR spectroscopy and mass spectrometry.