Fray, M. Jonathan; Allen, Paul; Bradley, Paul R.; Challenger, Clare E.; Closier, Michael; Evans, Tim J.; Lewis, Mark L.; Mathias, John P.; Nichols, Carly L.; Po-Ba, Yvonne M.; Snow, Hayley; Stefaniak, Mark H.; Vuong, Hannah V. Heterocycles, 2006 , vol. 67, # 2 p. 489 - 494