The Pterocellins, Novel Bioactive Alkaloids from the Marine Bryozoan <i>Pterocella </i><i>v</i><i>esiculosa</i>

Two new alkaloids, pterocellins A and B, have been isolated from the New Zealand marine bryozoan <i>Pterocella vesiculosa</i>. Structural elucidation was achieved through NMR and mass spectral analysis in conjunction with a single-crystal X-ray diffraction study of pterocellin A. The pterocellins possess a novel heterocyclic skeleton and exhibit potent antitumor activity and antimicrobial activity in vitro but only modest activity in the in vivo hollow fiber assay at the National Cancer Institute.