3-Acetyl and 3-decanoyltetramic acids with various substituents at the 5-position and their copper complexes, which possess a tricarbonylmethane structure, were prepared and tested for antimicrobial activity. 3-Decanoyltetramic acid derivatives and their copper complexes inhibited the growth of Bacillus subtilis and Staphylococcus aureus, but did not inhibited the growth of gram-negative bacteria and molds. 3-(1-Iminoethyl)-tetramic acids and their copper complexes were synthesized and tested for inhibitory activity towards chlorophyll development in plants.