Chapter Three 3-Alkylpiperidine alkaloids isolated from marine sponges in the order haplosclerida

Abstract

The first 3-alkylpiperidine sponge alkaloids, the halitoxins 31, were discovered less than twenty years ago [25]. Since that time, more than one hundred biogenetically related alkaloids have been isolated from marine sponges in the order Haplosclerida. As a group, the 3-alkylpiperidines are characterized by the diversity and complexity of their chemical structures and by the range of biological activities that they exhibit. To date there are eleven macrocyclic skeletons known among the 3-alkylpiperidine alkaloids. These include the haliclamine/cyclostellettamine, ingenamine, madangamine, ircinal, manzamine, halicyclamine, saraine 1-3, saraine A to C, petrosin, xestospongin/araguspongine and aragupetrosine skeletons shown in Figure 3.11. Three of these skeletal types, belonging to the ingenamine [52], madangamine [69] and halicyclamine alkaloids [42], were first reported in the single year 1994. In addition, it has recently been recognized that the papuamine [64] and manzamine C [58] skeletons are biogenetically related to the 3-alkylpiperidines. Therefore, the evidence to date indicates that the ammonia, propenal and long chain dialdehyde units that are the putative biogenetic precursors to the 3-alkylpiperidine alkaloids can be combined in a wide variety of ways to generate complex structures and it is reasonable to expect that many more alkaloid skeletal types will be discovered in Haplosclerida sponges in the years to come.