New coumarins from Pterocaulon polystachyum

Aerial parts of Pterocaulon polystachyum from Chaco province, Argentina, af forded the known coumarins ayapin, isoscopoletin, prenyletin, prenyletin me thyl ether, virgatenol, obtusinin, 5-methoxy-6,7-methylenedioxycoumarin, 5- (3,3-dimethylallyloxy)-6,7-methylenedioxycoumarin, 5-(2,3-dihydroxy-3-methy lbutanoxy)-6,7-methylenedioxycoumarin, haplopinol methyl ether, 6-(1,1-dime thyl-2-propenyl)-7-hydroxycoumarin and demethylnieshoutin; the last two are new as natural products while the five new coumarins from the collection w ere isovirgatenol, 3'-deoxyobtusinin, 6-methoxy-7-(2'-hydroxyethoxy)-coumar in, 5-(2 -hydroxyethoxy)-6,7-methylenedioxycoumarin and a substance tentati vely identified as 5-hydroxy-6,7-methylenedioxy-8-(3,3-dimethylallyl)-couma rin.