Chemical investigation of the marine ascidian Didemnum chartaceum from the Indian Ocean has resulted in the isolation of four new alkaloids of the recently reported lamellarin class. The structure of lamellarin E (2) was determined by spectroscopic and X-ray crystallographic methods. The structures of lamellarins F-H (3-5) were elucidated by interpretation of NMR spectral data, which relied heavily upon 1JC-H and 2-3JC-H correlation experiments. Isolation of lamellarins E-H from D. chartaceum indicates that lamellarins A-D, isolated from the prosobranch mollusc Lamellaria sp., were most likely sequestered from an ascidian in the diet of this mollusc. © 1988, American Chemical Society. All rights reserved.