ONE STEP PREPARATION OF ALLYL-β-d-DIOSIDES FROM SUSTAINABLE RESOURCES
The allyl group is one of the most useful functionalisation of the anomeric position of saccharides for two main reasons: (1) it can be orthogonally removed through the use of various reagents at any time in the synthesis of oligosaccharides,[1] (2) it can be functionalized to create biologically active neoglycoconjuguates,[2] which is one of our major interests in our laboratory.[3],[4]
To minimize the number of steps in the synthesis of neoglycoconjuguates, we have envisaged a direct preparation of allyl-β-d-diosides from natural disaccharides (Figure 1). Conventional methods for the preparation of such disaccharide units requires three to four steps and often the use of metal salts in large quantities. Anomeric O-alkylation is an efficient but often neglected strategy to prepare simple glycosides.[5],[6] Thus, we have optimized reaction and purification conditions for the chemoselective anomeric O-alkylation of unprotected disaccharides in water. Applying this method to biosourced disaccharides, we were able to prepare allyl-β-d-diosides on multigram scale in a single step in 45% to 55% isolated yields.
Figure 1. Preparation of allyl-β-d-diosides from biosourced disaccharides.
[1] Stick, R. V.; Williams, S. Carbohydrates : The Essential Molecules of Life, Elsevier, Amsterdam,
2009, pp. 35-74.
[2] Toyokuni, T.; Singhal, A. K. Chem. Soc. Rev. 1995, 24, 231-242.
[3] Lubineau, A.; Gavard, O.; Lortat-Jacob, H.; Sarrazin, S.; Bonnaffé, D. Chem. Eur. J. 2004, 10,
4265-4282.
[4] Baleux, F.; Loureiro-Morais, L.; Hersant, Y.; Clayette, P.; Arenzana-Seisdedos, F.; Bonnaffé,
D.; Lortat-Jacob, H. Nat. Chem. Biol. 2009, 5 (10), 743-748.
[5] Schmidt, R. R. Angew. Chem. Int. Ed. Engl. 1986, 25, 212-235.
[6] Lubineau, A.; Escher, S.; Alais, J.; Bonnaffé, D. Tetrahedron Let., 1997, 38, 4087-4090.
|
|
|
