1. Organic Chemistry Laboratory, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki, Helsinki, Finland, Finnish Institute for Verification of the Chemical Weapons Convention, P.O. Box 55, FIN-00014, University of Helsinki, Finland, and Institute for Preventive Medicine, Nutrition and Cancer, Department of Clinical Chemistry, P.O. Box 60, FIN-00014 University of Helsinki, Helsinki, Finland