Recent heterocyclic compounds from marine invertebrates: Structure and synthesis

A large variety of unique heterocyclic natural marine products, without terrestrial counterparts, have been isolated from marine invertebrates, mainly sponges, ascidians, and soft corals. Many of these compounds display interesting biological activity. In this review, we report our recent studies on nitrogen-containing heterocyclic compounds ("alkaloids"), as well as some containing sulfur and oxygen, which have been isolated from Red Sea and Indo-Pacific organisms, and discuss progress on the synthesis of these natural products and structural analogs.