Triplet photosensitization in cyercene A and related pyrones.
Mollusks of the Sacoglossa order contain a variety of polypropionate metabolites that are characterized by a pyrone chromophore, such as cyercene A and 9,10-deoxytridachione. Most often the pyrone is a 2-methoxy-gamma-pyrone but occasionally is a 4-methoxy-alpha-pyrone or hydropyrone. Members of this class of metabolites have been shown to undergo photochemical reactions of biosynthetic importance. An example is the photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione, which has been observed in several mollusks. In this report, a series of gamma-pyrones and their alpha-pyrone analogs were synthesized and analyzed for photosensitizing activity. In all cases studied, the gamma-pyrone was a more efficient triplet sensitizer than the corresponding alpha-pyrone. Included in this set of molecules was the Sacoglossan metabolite cyercene A and its alpha-pyrone isomer. When irradiated in the presence of oxygen, cyercene A produced singlet oxygen at significantly higher rate than the corresponding alpha-pyrone isomer. Furthermore, the photoisomerization of cyercene A was quenched by piperylene with con-committant isomerization of the piperylene indicating that the isomerization proceeded through a triplet excited state. In contrast, the isomerization of the alpha-pyrone analog was not quenched. The implications of these photochemical results in terms of the biosynthesis and biological activity of Sacoglossan polypropionate metabolites are discussed.
Department of Chemistry, Wake Forest University, 115-A Salem Hall, Winston-Salem, NC 27109, USA.
Daniel R
DR
Zuidema
Paul B
PB
Jones
D000818:Animals; D049851:Gastropoda / Q000378:metabolism; D015394:Molecular Structure; D008974:Mollusca / Q000378:metabolism; D018462:Photobiology; D010777:Photochemistry; D011753:Pyrones / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects*; D026082:Singlet Oxygen / Q000378:metabolism
D011753:Pyrones; C501019:cyercene A; D026082:Singlet Oxygen