1. Department of Chemistry Inorganic Chemistry University of Basel Spitalstrasse 51 4056 Basel Switzerland
2. Department of Chemistry Inorganic Chemistry University of Warwick Coventry CV4 7AL UK
3. Institute of Organic Chemistry and Biochemistry Centre of Novel Antivirals and Antineoplastics Academy of Sciences 16610 Prague Czech Republic
4. Centre of Novel Antivirals and Antineoplastics Vertex Pharmaceuticals Inc. 02210 Boston MA USA