1. S. Faham and D. C. Rees, Division of Chemistry and Chemical Engineering 147-75CH, California Institute of Technology, Pasadena, CA 91125, USA.
2. R. E. Hileman, J. R. Fromm, R. J. Linhardt, Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Iowa, Iowa City, IA 52242, USA.