Synthesis of Conformationally Restricted Glycoamino Acids using Fluorinating Agents

We have synthesized five- and six-membered ring, a/b- and a/g-glycoamino acids in our research group, since these compounds could serve as conformationallly restricted hybrid structural subunits for building more complex structures such as heterogeneous foldamers [1]. Starting from azide sugar 1 and applying the DAST reaction we obtained a rearranged, ring contracted structure [2] which was hydrolyzed, acetylated, and oxidized to produce 2. Following this synthesis route with attaching L-glycine through the carboxyl terminus side we prepared the respective a/b-glycoamino acid 3. At the present, we are focusing our attention in synthesizing this a/b-glycoamino acid at a higher scale by using other non-corrosive fluorinating agents. In a different set of reactions, the benzilidene group of compound 1 was hydrolyzed and oxidized selectively with TEMPO yielding 4 after acetylation. Further treatment of this compound incorporating L-glycine afforded the respective a /g-glycoamino acid 5 [1] Horne, W. S.; Gellman, S. H. Acc. Chem. Res. 2008, 41, 1399–1408. [2] Vera-Ayoso, Y.; Borrachero, P.; Cabrera-Escribano, F.; Gomez-Guillen, M.; Caner, J.; Farras, J. Synlett, 2010, 271-275.