Biosynthesis in opisthobranch molluscs: general outline in the light of recent use of stable isotopes.

The use of stable isotopes has been recently introduced in the biosynthetic studies of metabolites produced by opisthobranch molluscs. This methodology offers numerous advantages since it avoids the complex and tedious manipulations of potentially dangerous radioactive compounds and gives unequivocal evidence for the incorporation. In these studies, high field NMR spectroscopy is a particularly useful tool to localize the labeled atoms in the molecule. This chapter updates the biosynthetic studies on opisthobranch molluscs with particular attention to the recent experiments with precursors labeled with stable isotopes. Opisthobranchs are able to biosynthesize de novo a wide array of chemical skeletons including polyketides, polypropionates, acetogenins, and terpenoids. The studies regarding this latter class is proposed in the light of the recent debate about classical and independent mevalonate pathway.