Variation in the alkaloids among indo-pacific Leucetta sponges

Nine different Indo-Pacific collections of calcareous Leucetta sp. sponges were investigated for variation in their alkaloid constituents. These alkaloids consisted of 2-amino imidazoles such as dorimidazole A (1) and a polyunsaturated fatty amino alcohol (PUFAA), leucettamol A (3). The nine Leucetta species were divided into five different groups based on taxonomy. Significantly, six specimens contained leucettamol A (3), while the other three contained imidazoles, and these two classes of alkaloids did not occur in the same sponge sample. We recently found a Fijian Leucetta sponge that was a source of spirocyclopentimidazolidins, including spirocalcaridine A (4). We now show that another Fijian collection affords three amino imidazoles consisting of the known alkaloid naamine A (6) plus two new structures, N,N-dimethyl naamine D (5) and leucettamine C (7).