1. Department of Chemistry and the Ineos Oxford Institute for Antimicrobial Research Chemistry Research Laboratory Mansfield Road University of Oxford Oxford OX1 3TA UK
2. CBR Division Defence Science and Technology Laboratory (DSTL) Porton Down Salisbury SP4 0JQ UK
3. Present address: Leicester Institute for Structural and Chemical Biology and School of Chemistry University of Leicester Henry Wellcome Building, Lancaster Road Leicester LE1 7RH UK