Penienone was isolated from the culture filtrate of Penicillium sp. No.13 and completely inhibited hypocotyl elongation and root growth of lettuce seedlings at a concentration of 300 mg/l. In order to elucidate the active site of penienone, three derivatives were prepared and rested for their inhibitory activity against the growth of lettuce seedlings. The results indicated that hydroxymethyl group in the molecule of penienone was essential to exhibit the remarkable inhibitory activity against the growth of lettuce seedlings.
