ANOMERIZATION AND ANOMERIC EFFECT IN URONIC ACIDS

1,2-Cis-glycosyl residues often form components of a wide variety of natural glycosides, many of which display significant biological roles and therapeutic potential. Synthesis approaches can be compromised when it comes to preparing 1,2-cis glycosides and some give a mixture of anomers.

The Murphy group have synthesized α-glycosides, particularly glucuronides and galacturonides through the use of a chelation induced anomerization ^1-2. High α-selectivites are possible, particularly for uronic acids, which could be due to a stronger anomeric effect in such saccharide derivatives. This highly stereoselective method is an accessible, direct route to the corresponding 1,2-cis glycoside, and if developed further could possibly be used to convert 1,2-trans glycosides to 1,2-cis glycosides.

The synthesis of a range of hemi acetals of glucuronic acids A will be presented and the anomeric effects in such compounds (α:β ratios) will be discussed and compared with corresponding glucosides B. Attempts to correlate this data with stereoselectivities obtained in chelation induced anomerisation reactions will be presented.

Acknowledgment: The authors are grateful to Science Foundation Ireland for funding (Grant No. 12/IA/1398)

References

1. Pilgrim, W.; Murphy, P. V., J. Org. Chem. 2010, 75, 6747-6755

2. Pilgrim, W.; Murphy, P.V., Org. Lett. 2009, 11, 939-942