This book is a compilation of the latest achievements of leading researchers in marine natural products with extremely diverse structures and biological activities. It presents discussions of isolation, structure elucidation, biosynthesis, total synthesis, and biochemical properties of the compounds with characteristic structures such as macrolides, cyclic depsipeptides, alkaloids, and water-soluble heterocyclic low-molecular-weight compounds, from sponges, bacteria, cyanobacteria, flagellates, and other such organisms. The book especially focuses on heterocyclic natural products as a title in the book series, Topics in Heterocyclic Chemistry.