New nitrogenous constituents from the South African marine Ascidian Pseudodistoma sp.

Cytotoxicity-guided fractionation of an extract of the South African marine ascidian Pseudodistoma sp. provided pseudodistamine (1), a new bis alkyl amine, two new aliphatic amines 2 and 3, and a new β-carboline alkaloid 4. The structures of compounds 1–4 were elucidated by spectroscopic methods and by comparison with spectral data from structurally related compounds. The absolute stereochemistry of 1 was assigned by Mosherʹs ester analyses, while the stereochemistry of 2 and 3 was established by degradation and derivatization studies. Compound 2 demonstrated cytotoxic activity against four different human tumor cell lines, with an IC50 of approximately 6.0 μg/mL.