Bromopyrrole alkaloids isolated from the Patagonian bryozoan Aspidostoma giganteum

Abstract

Nine new bromopyrrole alkaloids, aspidostomides A–H and aspidazide A (1–9), were isolated from the Patagonian bryozoan Aspidostoma giganteum. Aspidostomides A–H have dibromotyrosine- or bromotryptophan-derived moieties forming either linear amides or pyrroloketopiperazine-type lactams with a bromopyrrole carboxylic acid as a common structural motif. On the other hand, aspidazide A is a rare asymmetric acyl azide formed by an N–N link of two different pyrroloketopiperazine lactams and is the first isolated compound of this class from marine invertebrates. This work is the first report of secondary metabolites isolated from a bryozoan from the Patagonian region. The structures of compounds 1–9 were elucidated by spectroscopic methods and chemical transformations. One of these compounds, aspidostomide E (5), was moderately active against the 786-O renal carcinoma cell line.