Syntheses, Enantioselective Separations of Photocyclodienes and their Prevalence in Ringed Seal

Persistent halogenated xenobiotics such as chlorinated cyclodienes are known to be subject to atmospheric longrange transports into Arctic and Antarctic regions [Arctic Monitoring and Assessment Programme (AMAP) 2004]. As a consequence, chlordane, a complex mixture of various chemically similar components, has been detected in biota of these remote areas. Among the major constituents of this mixture are cisand trans-chlordane, trans-nonachlor and heptachlor. The chlordane components are metabolized in almost all organisms into two persistent epoxides, oxychlordane and heptachlorepoxide. This biotic transformation pathway has been documented in many publications. However, much less effort has been devoted to the photoconversion products of the cyclodiene pesticides, which are being formed during the aerial transport. This may be surprising, because of their higher toxicities and stabilities in the environment in comparison with the parent compounds1. For example, as compared to heptachlor, its abiotic photoconversion product photoheptachlor was found to be 47 times more toxic to bluegill, 19 times to rat, 4 times to housefly, and 264 times to goldfish. It is also much more toxic to bluegill (4 times) and rat (16 times than heptachlorepoxide).