Further Studies on the Chemistry of the Flustra Alkaloids from the Bryozoan Flustra foliacea

Since 1980, over a dozen novel brominated alkaloids, named flustramines, have been isolated from Scandinavian and Canadian collections of the marine bryozoan Flustra foliacea. This paper describes the reisolation of the known compound dihydroflustramine C (1) and the isolation of 11 new flustramines (2-4, 6-13), including two dimers (12, 13) that may be isolation artifacts. Together these compounds, some with an unexpected aryl substitution pattern, reveal an intricate network of metabolites present in the extracts of the bryozoan. The structures of these metabolites were solved using a variety of spectroscopic techniques and chemical derivatization and modification. This work also led to the recognition of an unusual rearrangement reaction that occurred slowly over a number of years.