The structure of acridone alkaloid atalaphyllidine from the root bark of Atalantia monophylla Correâ (Rutaceae) has been established as 2', 2'-dimethyl-[pyrano 5', 6': 3, 4]-1, 5-dihydroxy acridone via spectroscopic data and chemical reactions. A novel group of compounds characterized by saturated, mono- and di-unsaturated long alkyl chains linked at position 3 of pyrrol-2-aldehyde, pyrrol-2-carboxylic acid, and 2-carbomethoxy moieties, including corresponding carboxylic acids and methyl esters, has been isolated from the marine sponge Oscarella lobularis. Additionally, two chiral neuroleptic agents with stereospecific biological activity are reported: methotrimeprazine (more potent in its (-)-enantiomer) and butaclamol ((+)-enantiomer as potent as fluphenazine). The absolute configuration of (-)-methotrimeprazine is unknown, while that of (+)-butaclamol was determined by X-ray crystal structure analysis. It is now found that the neuroleptic activity of octoclothepin is confined to its (+)-enantiomer, a finding at variance with earlier results.