TRANSFORMATION OF TERPENE PIQUEROL A TO HYDROQUINONE AND PHENOLIC DERIVATIVES - EFFECT OF THESE COMPOUNDS ON WEEDS

Piquerol A (Ia), an allelopathic terpene from Piqueria trinervia (Aste raceae) was chemically transformed into its diacetate (Ib), benzylic a lcohol (II), dialkyl hydroquinone derivative (IIIa and IIIb), and phen olics (IVa and V). The structures of these derivatives were determined by spectral analysis. Piquerol derivatives were found to act as power ful radicle growth inhibitors of the weed Amarantus hypochondriacus. O rder of inhibition was Ib > IIIa > Ia > IVa > II. The first three comp ounds were also radicle growth inhibitors of the weed Echinocloa crusg alli.