Cyclo-(L-tryptophyl-L-phenylalanyl) was isolated from an unidentified Penicillium sp. The absolute configuration of the compound was confirmed to be S, S at C-11 and C-14 by means of the comparison of the CD spectrum with that of the synthetic compound synthesized from L-tryptophan and L-phenylalanine. Cyclo-(L-try-L-Phe) and its components, L-tryptophan and L-phenylalanine, exhibited different biological activities against the tested plants of pine and tea pollen, lettuce, cress and rice seeds. Therefore, the biological activities of cyclo-(L-Trp-L-Phe) result from the intact compound and not the-degradation to L-tryptophan and L-phenylaianine.
