Terpenoids sesquiterpene alkaloids

The close relationship of cyclization modes existed in sesquiterpene biosynthetic machinery, with those presented by the metal-catalyzed cycloisomerizations, justify the vast amount of reports on total synthesis of sesquiterpenes, in which the utilization of enyne or diene cycloisomerizations are the key components of their synthetic strategy. This chapter is intended to cover only selected examples on the topic. Special concern is given on covering catalyzed reactions, which are triggering different cyclization modes, only for the construction of sesqniterpene core strnctnres. Assuredly, cycloisomerization reactions are powerfnl tools in providing also other classes of secondary metabolites, as complex terpenoids and alkaloids, in which the readers are referred to more general reviews on the topic [26,30]. 

Terpenoids and alkaloids are the most diverse substances isolated from marine invertebrates [5,15]. Almost 98% of metabolites extracted from cni-darians are from the class Anthozoa where terpenoids dominate across the subclass Octocorallia [5,15] (Figs. 2 and 3). The order Alcyonacea (mainly the families Alcyoniidae and Xeniidae) produce half of the metabolite richness within the subclass (Fig. 1). The genus Sinularia (Alcyoniidae), for example, produces a great variety of chemical compounds ranging from sesquiterpenes to diterpenes [93]. The suborder Stolonifera (order Alcyonacea) and the orders Pennatulacea and HeUoporacea all produce isoprenoids as predominant compounds. 

There are abundant and diverse flavonoids with carbohydrates and lipids, alkaloids (betalain alkaloids and other alkaloids), phenols (chromones, cou-marins, lignans, quinines, and other phenolics), terpenoids (monoterpenoids, sesquiterpene lactones, triperpenoid saponins, carotenoids, and other terpenoids), and minerals as micronutritional phytochemicals in fruits and vegetables of our daily diets. Among these phytochemicals, the flavonoids have specific functionality in relation to age-related diseases such as hypertension, diabetes, cardiac infarction, cataracts, and cancer. The authors of each chapter in the first section have presented their evidence in relation to the mechanism of the preventative and therapeutic ability of the compounds. 

Cl 0 monoterpenes Cl 5 sesquiterpenes C20 diterpenes C30 triterpenes C27 steroids C40 tetraterpenes C(n) polyterpenes Saponins Cucurbitacins Terpenoid alkaloids... 

Alkaloids can be divided into different t q3es according their pure chemical structures pointing first at the alkaloid base, a basic chemical nucleus. The following are basic types of alkaloids acridones, aromatics, carbo-lines, ephedras, ergots, imidazoles, indoles, bisindoles, indolizidines, manza-mines, oxindoles, quinolines, quinozolines. quinolizidines, phenylisoquinolines, phenylethylamines, piperidines, purines, pyrolidines, pyrrolizidines, pyrro-loindoles, pyrydines, sesquiterpenes, simple tetrahydroisoquinolines, stereoids, tropanes, terpenoids, diterpenes, and triterpenes. 

Phytochemistry Leaves contain alkaloids, glycosides, bitter substances, sesquiterpene lactones (arctiopicrin and onopor-dopicrin), vitamin C and K, resins, titratable acids, sugars, tannins, terpenoids (taraxasteryl acetate), etc. Seeds contain alkaloids, acetates of lupeol and amyrin, and drying fatty oil (Khalmatov et al. 1984 Ul chenko et al. 1993 Khalilova etal.2004). 

Mono- and sesquiterpenes are the main constituents of the essential oils, while the other terpenes are constituents of balsams, resins, waxes, and rubber. Oleoresin is a roughly equal mixture of turpentine (85 % Cio-monoterpenes and 15 % C15- sesquiterpenes) and rosin (C2o-diterpene) that acts in many conifer species as a toxic material to invading insects and their pathogenic fungi [12]. A number of angiosperm species have inducible terpenoid defensive compounds (phytoalexins) [13]. These include both sesquiterpenoid and diterpenoid t)pes. Isoprenoid units are also found within the framework of other natural molecules. Thus, indole alkaloids, several quinones (vitamin K), alcohols (vitamin E, vitamin A formed from p-carotene), phenols, and isoprenoid alcohols (also known as terpenols or polyprenols) also contain terpenoid fragments. The biogenesis. 

Alkaloids from the water Hly genus Nuphar include monomeric (C15) sesqui-terpenoid piperidines and quinoHzidines, and dimeric (C30) thiospirane metabolites in which two quinohzidine moieties are linked by a spirocyclic tetrahydrothiophene ring. The terminus of the regular sesquiterpene backbone in all of these alkaloids has been elaborated into a 3-furyl ring. Only the simple monomeric alkaloids are germane to the current review. 

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