Six new guanidine compounds, named minalemines A-F 2, were isolated from the marine tunicate Didemnun rodriguesi by careful HPLC separation. Their structures were elucidated by MS, 1D- and 2D-NMR spectral analysis, and chemical degradation. These compounds incorporate one agmatine (Agma) and one homoagmatine (Hagma) terminal unit with their guanidine groups free and the primary amino groups linked through a peptidic bond to L-Leu and a very rare fl-N-carboxymethyl amino acid (Ncma) bearing a saturated long chain. The saturated chains of minalemines A-C are homologs (C7, C8, and C9 respectively). Minalemines D-F are the sulfamic acid derivatives of minalemines A-C and constitute the first examples of such a functional group in a marine organism.