Facilitating structural elucidation of carbohydrates using selective TBDPS protection of primary hydroxyl groups and in situ "isotagging" of sugars in the NMR tube

WCC 12

Katherine J. Mackenzie, kmackenz@uci.edu1, Alpay Dermenci2, Omid Khakshoor3, Lupe Mejorado4, James S. Nowick, jsnowick@uci.edu1, Scott Rychnovsky, srychnov@uci.edu5, and AJ. Shaka1. (1) Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, (2) Department of Chemistry, Yale University, (3) Department of Chemistry, Stanford University, (4) Auspex Pharmaceuticals, (5) Department of Chemistry, UC Irvine, 1102 NS 2, Department of Chemistry, Irvine, CA 92697
The highly reactive compound trichloroacetyl isocyanate (TAI) replaces carbohydrate hydroxyl groups with carbamate groups, causing the proximal ring proton signals of TAI-reacted carbohydrates to be dispersed and shifted downfield. This allows for identification of ring protons as primary or secondary, assisting in structural elucidation of the carbohydrate. The reaction produces no side products and can be performed in an NMR tube. Furthermore, TAI can be enriched with 13C and 15N and used to “isotag” carbohydrates, allowing for multidimensional NMR analyses. Because it is so reactive, TAI is incompatible with many common solvents. Selectively protecting the primary hydroxyls with tert-butyldiphenylsilyl (TBDPS) allows for dissolution of small carbohydrates in CDCl3. TAI reacts with the remaining hydroxyl groups without displacing TBDPS, and the 1H-NMR spectrum shows peak dispersion characteristic of a TAI-reacted carbohydrate without overlapping of TBDPS and carbohydrate peaks.
 

The Merck Index Women in Chemistry
2:30 PM-4:30 PM, Monday, August 17, 2009 Walter E. Washington Convention Center -- Hall D, Poster

Women Chemists Committee

The 238th ACS National Meeting, Washington, DC, August 16-20, 2009