1. Institut de recherches cliniques de Montréal (IRCM), Bio-organic Chemistry Laboratory, 110 avenue des Pins Ouest, Montréal, Québec, Canada H2W 1R7, Department of Chemistry and Department of Biochemistry, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec, Canada H3C 3J7, and Bio-Méga Research Division, Boehringer Ingelheim (Canada) Ltd., 2100 rue Cunard, Laval, Québec, Canada H7S 2G5