Iridoids chemistry

Jensen, S.R., Plant iridoids, their biosynthesis and distribution in angiosperms, in Ecological Chemistry and Biochemistry of Plant Terpenoids, Harbome, J.B. et al., Eds., Clarendon Press, Oxford, 1991, 133. 

Kotsos, M. et al., Chemistry of plants from Crete stachyspinoside, a new flavonoid glycoside and iridoids from Stachys spinosa, Nat. Prod. Lett., 15, 377, 2001. 

Galvez M, Martin-Cordero C, Ayuso MJ. Pharmacological Activities of Iridoids Bio-S3mthesized by Route II. Studies in Natural Products Chemistry 2005 32 365- 394. 

Yang XP, Li EW, Zhang Q, Yuan CS, Jia ZJ. Eive New Iridoids from Patrinia rupestris Chemistry. Biodiversity. 2006 3 762-770. 

Tundis R, Loizzo MR, Menichini F, Statti GA, Menichini F. Biological and Pharmacological Activities of Iridoids Recent Developments. Mini-Reviews in Medicinal Chemistry 2008 8 399-420. 

Kupchan SM, Dessertine AL, Blaylock BT, Bryan RF. Isolation and Structural Elucidation of Allamandin, an Antileukemic Iridoid Lactone from Allamanda cathartica. Journal of Organic Chemistry 1974 39(17) 2477-2482. 

Stephens PJ, Pan JJ, Krohn K. Determination of the Absolute Configurations of Pharmacological Natural Products via Density Functional Theory Calculations of Vibrational Circular Dichroism The New Cytotoxic Iridoid Piismatomerin. Journal of Organic Chemistry 2007 72(20) 7641-7649. 

Ye G, Yang YL, Xia GX, Fan MS, Huang CG. Complete NMR Spectral Assignments of Two New Iridoid Diastereoisomers from the Flowers of Plumeria rubra L.CV. acutifo-lia. Magnetic Resonance in Chemistry 2008 46(12) 1195-1197. 

A.Bianco, The Chemistry of Iridoids, in, Atta-ur-Rahman Ed., Studies in Natural Products Chemistry, Elsevier, Vol 7 p. 439 (1990). 

Melendez G. Estudio Quimico del Boschnalosido (Iridoide glicosidico). B.S. Thesis (Chemistry), Uniyersidad Nacional Autonoma de Mexico Mexico, 1989. 

Fig. 20.5. Proposed cyclization of iridoid monoterpenes (modified from Escher et al., 1970 used with permission of the copyright owner, the Royal Society of Chemistry, London).

Bowers, M. D., Chemistry and coevolution Iridoid glycosides, plants, and herbivorous insects, in Chemical Mediation of Coevolution (K. C. Spencer, ed.), 133-165, Academic Press, San Diego, CA, 1988. 

Biosynthesis characterization chemistry classification iridoids pharmacology secoiridoids synthesis... 

Bianco A (1990) The chemistry of iridoids. In Rahman A (ed) Studies in natural products chemistry, vol 7. Elsevier, Amsterdam, p 329... 

Monoterpenes and iridoids are important classes of secondary metabolites, and their biosynthesis as well as total synthesis approaches to access these compounds has attracted the interest of chemists for a long time. This overview will summarize the most important biosynthesis pathways and in addition will illustrate how one of the most important recent developments in organic chemistry, asymmetric organocatalysis, contributed in the development of total synthesis approaches toward these compounds. Therefore, a comprehensive introduction to asymmetric organocatalysis will be given as well. However, it should be noted that the applicability of this methodology to the synthesis of natural products is of course not only limited to monoterpenes and iridoids but holds much promise for other classes of primary and secondary metabolites as well. 

Iridoids are a large and stmcturally diverse class of secondary metabolites of monoterpenoid origin [10, 11]. Their sttuc-tural parent system is the iridane skeleton, which is derived from geraniol (6) by a cyclization pathway that is mechanistically different to the cyclization reactions that are usually found in classical terpene chemistry [1, 12], Further enzymatic transformations then give the fundamental iridoid skeleton or the thereof derived secoiridoid motive (with an alternative connectivity as shown in Scheme 6.10), which often serves as a building block for the synthesis of more complex monoterpenoid indole alkaloids [1]. Noteworthy, hereby the isoprene mle is often not fulfilled anymore as the terpenoid parts of such compounds sometimes contain nine carbon atoms only due to a decarboxylation step somewhere in the sequence. Very often iridoids and secoiridoids are present as glycosides in nature. 

Monoterpenes and iridoids are very important natural products, and the biosynthetic pathways toward these compounds are nowadays well understood. We choose this class of secondary metabolites to highlight the potential of asymmetric organocatalysis for the total synthesis of complex natural products. Asymmetric organocatalysis has been one of the most exciting fields in organic chemistry over the last decades, and we hope that we have been able to illustrate how diverse and powerful this methodology can be with respect to different activation modes that are possible and different substance classes that can be easily accessed thereby. 

Loganin is an iridoid glucoside which occupies a central position in the biosynthesis of Corynanthe, Aspidosperma, Iboga, Ipecacuanha, Cinchona, and structurally simpler monoterpene alkaloids. For a review of the extensive researches that led to confirmation of the key role of loganin in alkaloid biosynthesis, see A. R. Battersby, Biochem. Soc. Symp., 29, 157 (1970) A. R. Battersby, Chem. Soc. Spec. Period. Rep., 1, 31 (1971) A. I. Scott, Accts. Chem. Res., 3, 151 (1970). For a useful account of the chemistry of iridoid glucosides see, J. M. Bobbitt and K. -P. Segebarth in Cyclopentanoid terpene Derivatives, Eds., W. I. Taylor and A. R. Battersby, Marcel Dekker, New York, 1969, p 1. 

Chemistry largely unknown possibly cyanogenetic. Ryania has reputedly toxic members with nitrogenous insecticidal substances Bitter substances (presumably iridoid glycosides) present... 

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