Synthesis of carotenoid-monosaccharide conjugates via azide–alkyne click-reaction

Carotenoid pentynoates were coupled to protected and unprotected sugar azides via an azide-alkyne click-reaction using bis-triphenylphosphano-copper(I)-butyrate (C3H7COOCu(PPh3)2) complex. Protected sugars delivered the conjugates with excellent yields, whereas with unprotected ones amphipathic carotenoid-sugar derivatives were obtained in good or moderate yields in a simple way.