Cross metathesis for the synthesis of novel C-sialosides

Cross metathesis of both anomers of C-allyl sialoside (3α/3β) with styrene catalyzed by the second generation Grubbs or Hoveyda-Grubbs catalysts gave the corresponding aryl derivatives (4α/4β) in virtually quantitative yields. The products were hydrogenated to model compounds 5α/5β. Similarly, reaction of the α-anomer 3α with galactose derivative 8 gave the olefin-linked disaccharide mimetic 9. Following hydrogenation and deprotection, the ethylene-bridged Neu5Acα(2→6)Gal analogue 11 could be obtained.