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.
Zuidema
Daniel R
DR
Department of Chemistry, Wake Forest University, 115-A Salem Hall, Winston-Salem, NC 27109, USA.
Jones
Paul B
PB
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