Protobruceols: New 6-C-Monoterpenyl-5,7-Oxygenated Coumarins From Eriostemon Brucei

摘要

Six novel coumarins have been isolated from the aerial parts ofEriostemon bruceivar.cinereus.Five had the same tricyclic nucleus (+)-2-methyl-5-hydroxy-2H-benzo-1,2b:3,4b#x2032;-dipyran-8-one and varied only in the C-2 substituent,viz.4-methylpent-3-enyl (protobruceol-1), 4-hydroxy-4-methylpent-2(E)-enyl (protobruceol-II), 4-hydroperoxy-4-methylpent-2(E)-enyl (protobruceol-II hydroperoxide), 3-hydroxy-4-methylpent-4-enyl (protobruceol-III), 3-hydroperoxy-4-methylpent-4-enyl (protobruceol-III hydroperoxide). A sixth coumarin was characterised as the linear annellated isomer of protobruceol-II, (+)-2-methyl-2-(4-hydroxy-4-methylpent-2(E)-enyl)-5-hydroxy-2H-benzo-1,2b:5,4b#x2032;-dipyran-8-one (protobruceol-IV)