1. a Millennium Pharmaceuticals Inc. , 75 Sidney Street, Cambridge, MA, 02139, USA
2. b Department of Chemistry , American University of Sharjah , P.O. Box 26666, Sharjah, United Arab Emirates
3. c Department of Chemistry , McGill University , Montreal, H3A 2K6, Quebec, Canada
4. d Department of Chemistry , San Jose State University , One Washington Square, San Jose, CA, 95192-0101, USA