Natural product synthesis large biologically active compounds

It is interesting that the retrosynthetic approach to heterocycles is not considered in monographs or review articles on the synthesis of individual classes of heterocyclic compounds. The examples that follow illustrate the retrosynthetic approach to the five- and six-membered heterocyclic structures often encountered in natural or synthetic biologically active compounds. Examples 7.2, 7.3, 7.6, 7.11 and 7.12 demonstrate syntheses of biologically active compounds developed to large-scale production by chemists at PLIVA Co. (Croatia). 

Among the various classes of natural products, the terpenoids have sometime occupied a special position and received chemist s attention. A large number of these compounds exhibit significant biological activities such as antifungal, antibacterial, antiviral, antitumor and insecticidal properties. The interest in this type of natural products is manifested by a large number of articles dealing with their isolation and synthesis that appear in scientific literature [1]. In recent decades an enormous effort has been focused on the development of new methods for the stereoselective synthesis of the above-mentioned diterpenes. 

Natural Product Chemistry continues to present exciting opportunities for medicinal chemists to discover new bioactive compounds against various diseases. Even in cases where the structures are too complex to be obtained on a large scale by synthesis, the interest is often focussed on those portions of the stnictures which are responsible for the biological activity and which can serve as simpler pharmacophores for synthesis and study of structure-activity relationships. The enormous structural diversity offered by natural products of terrestrial and marine origin therefore offers a vast resource to medicinal chemists in search for new bioactivity profiles or mechanisms of actions. 

---