RESUMO
Linear-type furocoumarins, 5-[(2"E,6"R)-6"-hydroxy-3",7"-dimethylocta-2",7"-dienyloxy]psoralen and 5-[(2"E,6"S)-6"-hydroxy-3",7"-dimethylocta-2",7"-dienyloxy]psoralen (1) were first isolated from whole plants of Seseli hartvigii together with one new natural product 6-(3'-methyl-2'-oxo-3'-butenyl)-7-methoxycoumarin (2), and four known compounds (tamarin, bergaptol, notoptol, and a mixture of beta-sitosterol and stigmasterol). The structure of 1 was elucidated by extensive spectroscopic analysis and chemical conversion. The modified Mosher's method and HPLC were applied to determine its stereochemistry. Both R- and S-configurations exist in 1; after modification by Mosher's reagent, they were effectively separated, and their ratio was deduced to be 59% and 41%, respectively.
