Poly terpenoids

Much of the current interest in poly terpenoids is concerned with their biological role. The C55 prenol (68 n = 3, m = 8) from Staphylococcus aureus was shown ... 

Ruzicka, L., and S.L. Cohen Polyterpenes and Poly terpenoids. 113. Oxidation in the Oleanolic Acid Series without Rupture of the Ring System. Nature of the Fourth Oxygen Atom of Glycyrrhetic Acid. Helv. Chim. Acta, 20, 804 (1937). 

D-Mevalonic acid is the fundamental intermediate in the biosynthesis of the terpenoids and steroids, together classed as poly-isoprenoids. The biogenetic isoprene unit is isopentenyl pyrophosphate which arises by enzymic decarboxylation-dehydration of mevalonic acid pyrophosphate. D-Mevalonic acid is almost quantitatively incorporated into cholesterol synthesized by rat liver homogenates. 

Last but not least, a very intriguing terpenoid pyrrolidine alkaloid, poly-zonimine was milked from the millipede Polyzonium rosalbum (148). The structural formula of polyzonimine (118) is based on an X-ray crystallographic analysis of its perchlorate and by a total synthesis. 

Piretti, M.V., Ghedini, M., and Serrazanetti, G., Isolation and identification of the poly-phenolic and terpenoid constituents of Vitis vinifera. v. Trebbiano variety. Ann. Chim. 66, 429, 1976. 

Fig. 4 Renewable platform chemicals used in olefin metathesis (a) plant oils and fatty acids, (b) terpenes and terpenoids, (c) phenylpropanoids, (d) natural rubber (cw-1,4-poly isoprene), (e) carbohydrates, (f) amino acids and peptides, and (g) furans...

C15), di- (C20), sester- (C25), tri- (C30), tetra- (C40), and poly- carboxylic acids and their esters, which makes terpenoids the... 

Biosynthetic studies showed that the aromatic ring was formed from a poly-ketide whilst the side chain was derived from the mevalonate terpenoid pathway. The C-5 O-methyl and C-4 methyl groups were derived from methionine. The high incorporation of 4,6-dihydroxy-2,3-dimethyl-[l- C]benzoic acid (4.37) suggested that the methylation at C-4 occurred at the polyketide stage prior to the formation of the phthalide. 5,7-Dihydroxy-4-methyl-[7- C]phthalide (4.38) and its 6-farnesyl analogue were also incorporated eiSciently into mycophenolic acid. The farnesyl precursor was detected as a metabolite of P. brevi-compactum and shown to be formed from 5,7-dihydroxy-4-methyl-[7- C]phthalide by a trapping... 

Terpene synthases constitute a large class of enzymes that are able to convert just a handful of linear isoprenoid precursors, made from IPP and DMAPP by prenyltransferases, into a large diversity of thousands of terpenoids. As most of the enzyme products are of (poly)cyclic nature, these enzymes are often called terpene cyclases. Two types of terpene synthases can be mechanistically distinguished by their formation of a reactive carbocationic species. Class I terpene synthases contain a highly conserved DDXXD motif as also found in a-type prenyltransferases and perform substrate ionization via metal-triggered abstraction... 

As presented in this chapter, today, much is known about the process of terpene biosynthesis. The accumulated knowledge includes a detailed picture about the biosynthesis of the terpenoid monomers IPP and DMAPP either via the mevalonate or the DXP route and their interconversion by isomerases. Also, the stereochemical courses and enzyme mechanisms of all transformations have been largely elucidated. Especially the recently obtained structural data of prenyltransferases and various kinds of terpene synthases resulted in an evolutionary model that involves six domains (a, P, 7,8, e, and Q for the biosynthesis of linear polyisoprenoids from IPP and DMAPP and their subsequent transformation into (poly)cyclic terpenes. All these insights may open up new chances in controlling terpene biosynthesis, e.g., by directed evolution of terpene cyclases or domain swaps in multi-domain enzymes for the production of new terpenes, reconstitution of terpene biosynthetic pathways in heterologous hosts for production optimization, or targeted inhibitirm of pathways in pathogens for disease control. 

Cationic cyclization is a common theme for the biosynthesis of a large number of polycyclic terpenoids and is partly responsible for the structural diversity of terpenoids that share the same poly-isoprene origin. Thus, it is not surprising that cationic transannular cyclization is also prominently featured in polycyclic terpenoids synthesis. 

Poly(a-pinene) 70750-57-1 Teipenes and terpenoids, turpentine-oil, cc-pinene fraction, polymd. s Unk... 

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