1. GSK Via Fiorentina 1 53100 Siena Italy
2. CIC bioGUNE Bizkaia Technology Park, Building 800 48160 Derio Spain
3. Department of Bioorganic SynthesisLeiden University 2333 Leiden The Netherlands
4. Basque Foundation for Science IKERBASQUE 8009 Bilbao Spain
5. Department of Organic Chemistry IIFaculty of Science and TechnologyUniversity of the Basque Country 48940 Leioa Spain