HIGHLY OXYGENATED COUMARINS FROM PELARGONIUM SIDOIDES

The range of natural simple coumarins is extended by discovery of the highly oxygenated representatives 6,8-dihydroxy-7-methoxycoumarin, 6,7 ,8-trihydroxycoumarin, 6,8-dihydroxy-5,7-dimethoxycoumarin, and 7-acet oxy-5,6-dimethoxycoumarin. They are accompanied in the roots of Pelarg onium sidoides by the widely occurring scopoletin, associated with the uncommon analogues 5,6,7-trimethoxycoumarin, 7-hydroxy-5,6-dimethoxyc oumarin (umckalin), and 5,6,7,8-tetramethoxycoumarin (artelin), these being reported from a plant source for the second time. The structures of these compounds were established from chemical and spectroscopic s tudies. Differentiation between oxygenation patterns is discussed on t he basis of chemical shift data.