Coumarins structural types

Structural types, in this section we will mainly focus our discussion on phenyl propanoids, coumarins, flavonoid and isoflavonoids, lignans and tannins. 

In addition to the structural types shown there are also homo-A., bis-A., and acrimarines (composed of A. and coumarin parts). 

Proton magnetic resonance spectroscopy is currently the most useful technique for the assignment of structure to a natural coumarin. Spectra-structure correlations have been compiled by Steck and Mazurek (567) to facilitate the rapid identification of the major structural types. 

In other important publications, data have been collected and interpreted for a variety of structural types, especially isomers, thereby aiding their identification 196, 215, 369, 419, 460—463, 473, 484). Long-range coupling 283), solvent- 103, 241, 413, 414) and lanthanide-induced shifts 238, 239) and, more recently, nuclear magnetic resonance spectroscopy 151, 362) have also proved of value in the structural assignment of coumarins. 

Coloring Aids Bisbenzoxazoles, triazinephenyl-coumarins, and bis(styrl)-bisphenyls comprise the most widely used structural types of coloring additives. Used in conjunction with dyes and pigments, coloring aids absorb ultraviolet radiation and emit a blue-violet fluorescence, making polymer surfeces appear bright or cleaner. 

Fig. 1), and angular type, generically known as angelicins, where the ring is attached to carbons 7 and 8 of the coumarin structure, for example, angel-icin (3) (Fig. 1). 

Another method for the isolation of furanocoumarins from plant materials is based on lactone type of coumarin structure. Alcohol or water-alcohol solutions of KOH break the lactone ring in coumarins (in a boiling water bath), giving rise to coumaric acids. Then, after acidification, these acids cyclize to coumarins again, and these coumarins can be extracted using ether. There are many disadvantages in the described method because coumarins are labile substances and are susceptible to acids and bases, which can destroy their epoxide structure and ester bonds in side chains. 

This limitation is well Illustrated by the failure of those methods to uncover the presence of another important group, the flavanoid, coumarin and cinnamic acid phenols (85 - 117). On the other hand, some 32 of these compounds were identified when isolation procedures specific for these types of compounds were employed. Using isolation and identification techniques which are particularly useful for alkaloids, it would be possible to determine whether any representatives of this class are present and, if so, to conduct subsequent studies for structure determination. 

Only two flavones of this type are known so far. They were reported from Gnidia soccotrana (Thymeleaceae). For formula see Figure 12.7. Similarly, only a few flavonols are known as hybrid structures, but none of them with coumarins (see Table 12.4). 

Fig. 5.16. Structures, 13C chemical shifts (in ppm) and one-bond carbon-hydrogen coupling constants (in IIz, italic types) of coumarin (left side) and the furanocoumarin psoralen (right side).

A photonic three-dimensional (3-D) crystal-type structure of a brominated thiirane/iodonium salt/ coumarin resin showed that it has a woodpile structure <2004JPST115>. 

The third chapter, Quantitative Structure-Cytotoxicity Relationship of Bioactive Heterocycles by the Semi-empirical Molecular Orbital Method with the Concept of Absolute Hardness by Mariko Ishihara, Hiroshi Sakagami, Masami Kawase, and Noboru Motohashi, presents the relationship between the cytotoxicity (defined as 50% cytotoxic concentration) of heterocycles such as phenoxazine, 5-trifluoromethyloxazoles, O-heterocycles such as 3-formylchromone and coumarins, and vitamin K2 derivatives against some tumor cell lines and 15 chemical descriptors. The results suggest the importance of selecting the most appropriate descriptors for each cell type and compound. The review is of interest as it represents the relationship of the molecular structures with the cytotoxic activity of these heterocycles. 

Because of the structural nature of the ADE systems, the most straightforward and obvious method to accomplish a model synthesis is by the implementation of a von Pechmann coumarin synthesis118 l31) on a suitable functionalized phloroglucinol derivative. These methods have indeed seen rather general utilization in their application to this type of model system synthesis. 

Abstract Construction of chemical libraries is a useful approach to the discovery of better fluorescent materials, and several types, such as styryl dyes and cyanine dyes, have been reported. In this chapter, we focus on construction of a library of chemicals having a coumarin skeleton as the core structure. Coumarin and its derivatives are key structures in various bioactive or fluorescent molecules, and their fluorescence properties are dependent on the precise structure, including the positions of substituents. 

Furanocoumarins are formed when furor ring is joined with coumarins. The plants of Rutaceae, Leguminosae and Apiaceae are rich sources of furanocoumarins. Depending upon the structure, the furanocoumarins are divided into linear and angular types. Furanocoumarin containing preparations are used externally as well as internally for treatment of leucoderma, psoriasis and skin carcinoma. 

Coumarin Derivatives Coumarins are known as an interesting class of laser dyes. Various structures are able to behave as type II photoinitiators (they work in their first excited singlet state) or to sensitize the photolysis of peresters or bis-aryl imidazoles [210] (see below). 

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