Macrocyclic structural classification

Different classifications for the chiral CSPs have been described. They are based on the chemical structure of the chiral selectors and on the chiral recognition mechanism involved. In this chapter we will use a classification based mainly on the chemical structure of the selectors. The selectors are classified in three groups (i) CSPs with low-molecular-weight selectors, such as Pirkle type CSPs, ionic and ligand exchange CSPs, (ii) CSPs with macrocyclic selectors, such as CDs, crown-ethers and macrocyclic antibiotics, and (iii) CSPs with macromolecular selectors, such as polysaccharides, synthetic polymers, molecular imprinted polymers and proteins. These different types of CSPs, frequently used for the analysis of chiral pharmaceuticals, are discussed in more detail later. 

Macrocyclic ligands will be classified, for the purposes of this article, as rings with at least nine members and three or more donor atoms. In a number of cases of unique structural units, elegant descriptive names have developed, which more appropriately describe the macrocyclic shape. Macrocycles will be classified as to donor types and, within the donor types, specific classifications of macrocycles will be noted where applicable. 

The ketone functional group appears in a wide variety of natural products ranging from the simple terpenes to complex macrocycles and polyfunctional molecules. This section will focus on simple, naturally-occurring ketones, largely from the terpene family, which illustrate relationships between structure and 1 0 NMR chemical shifts. Other more complex ketone containing structures will be examined later according to their natural product family classification, e.g. chromones, flavones, etc. 

There is no uniform classification for the A. In the literature divisions according to origin (examples Aconitum, Amaryllidaceae, Aspidosperma, cactus, Catharanthus, Cephalotaxus, Cinchona, coca, Corydalis, curare, Dendrobates, ergot, Erythrina, Iboga, Lycopodium, Maytenus, opium, Rauvol-fia, Senecio, Strychnos, tobacco, Vinca alkaloids, salamander, Solanum, Veratrum steroid alkaloids) in addition to divisions according to chemical structure (examples aporphine, benzylisoquinoline, bis-benzylisoquinoline, berberine, carboline, diterpene, inudazole, indole, indolizidine, isoquinoline, lupinane, macrocyclic, morphine, peptide, / -phenyl-ethylamine, piperidine, purine, pyridine, pyrrolidine, pyrrolizidine, quinoline, quinolizidine, quinucli-dine, spermine, spermidine, steroid, terpene, tro-pane, tropolone alkaloids) are used. 

All trichothecenes include the tricyclic 12,13-epoxytrichothec-9-ene core, 370. Based on this structure and its substitution pattern, the mycotoxins have been classified into four types, A (371), B (372), C (373), and D (374), by Ueno et al. Type A (371) can have a hydroxy group, an ester, or no functional group at C-8. Type B (372) possesses a carbonyl group at C-8, type C (373) has an epoxide function at C-7/C-8, and type D (374) mycotoxins are macrocyclic trichothecenes. Included among these four types there are some exceptions, which cannot be grouped accurately using this classification. Other classification systems for trichothecenes were proposed by Jarvis et al. (312) and Tamm et al. (313), but these will not be further discussed in this volume (Fig. 8.3). 

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