In the scope of a research program aiming to perform the synthesis and pharmacological evaluation of novel possible antitumour prototype compounds, we report in this paper the synthesis of new peptidyl derivatives from 4-thiazolidone nucleus. The synthesis reactions have been performed based in peptide synthesis as strategies. The characterisation of this new class of compounds was performed with IR and (1)H-NMR spectroscopy. In vivo, antitumour activity tests showed that some of these compounds were able to inhibit significantly sarcoma S-180 tumour growth in mice, revealing itself as a new potential class of drugs in cancer chemotherapy.