Terpenoid and Steroid Alkaloids

Abstract

The diverse group of natural products classed as terpenoids and steroids includes some compounds that contain nitrogen and are called alkaloids on that account. Biosynthetically they can be set apart from all other alkaloids because their carbon skeletons are derived from mevalonic acid, while most other alkaloids have their skeletons constructed largely of amino acid residues. This origin from a non-nitrogenous precursor raises a question as to the source of the nitrogen and the stage at which it enters the molecule. For the most part knowledge about the biosynthesis of these alkaloids is limited to the knowledge that they are indeed derived from mevalonic acid. In other cases even that conclusion is only an inference based on examination of structure. Certain alkaloids, otherwise non-terpenoid, that contain a terpenoid unit are also known and are treated in Chapter 10. Structures of some terpenoid alkaloids are given in Fig. 13-1.