title: Photochemistry of mycolactone A/B, the causative toxin of Buruli ulcer.
abstract: Photochemistry of mycolactone A/B and related unsaturated fatty acid esters is reported. On exposure to visible light, mycolactone A/B gave a mixture of four photomycolactones. Pentaenoates and tetraenoates, representing the unsaturated fatty acid portion of mycolactone A/B, were found to show the reactivity profile parallel with that of mycolactone A/B. The structure of the four photomycolactones was elucidated via (1) structure determination of the four photoproducts in the tetraenoate series; (2) their transformation to the photoproducts in the pentaenoate and then mycolactone series. Triplet quenchers did not affect the photochemical transformation, thereby indicating an event at the singlet state. A concerted, photochemically allowed [4πs + 2πa] cycloaddition was suggested to account for the observed result. This study provided the structurally defined and homogeneous material, which allowed demonstration that photomycolactones exhibit significantly reduced cytotoxicity, compared with mycolactone A/B.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Yalan
authors.initials: Y
authors.lastname: Xing
authors.forename: Sudhir M
authors.initials: SM
authors.lastname: Hande
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kishi
mesh_terms: D054312:Buruli Ulcer / Q000139:chemically induced*; D006801:Humans; D018942:Macrolides / Q000737:chemistry* / Q000633:toxicity*; D015394:Molecular Structure; D055668:Photochemical Processes; D013237:Stereoisomerism
chemical_list: D018942:Macrolides; C451488:mycolactone A; C451489:mycolactone B