1. Department
of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles E. Young Drive, Los Angeles, California 90095-1569, United States
2. Chemistry
Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
3. Department
of Chemistry, Columbia University, Havemeyer Hall, 3000 Broadway, New York, New York 10027, United States
4. Novartis Institutes for BioMedical Research, Inc., 250 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
5. Laboratory
for Bioorganic Chemistry, Sloan-Kettering Institute for Cancer Research, 1275 York Avenue, New York, New York 10065, United States