1. Department
of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
2. Organisch
Chemisches Institut, Universität Heidelberg, Im Neuenheimer
Feld 270, D-69120 Heidelberg, Germany
3. Department
of Chemistry, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States
4. Department
of Chemistry, Keene State College, Keene, New Hampshire 03435, United States