Cyclo-(l-tryptophyl-l-phenylalanyl), a plant growth regulator produced by the fungus Penicillium sp.

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-phenylalanine.