Coumarins structure

Substitutions in position 3 with electron-withdrawing groups such as -CN, -COR, -COOR, and -N02 or with alkyl groups increase the fluorescence intensity of the basic coumarin structure [29, 30],... 

Coumarins are pharmacologically active and have been used in the treatment of a diverse range of diseases. The great diversity of coumarin structures and their wide range of polarities present special problems for their simultaneous analysis. The separation of seven closely related coumarins by CZE was studied. Optimized conditions tallied with a 200 mM boric acid—50 mM tetraborate buffer pH 8.5 and were applied to the determination of coumarins in extracts from roots and aerial parts from the plant Chrysanthemum segetum. Baseline separation of six coumarins was achieved in 10 min. 

In this chapter, we described three examples of coumarin library synthesis, and showed that synthesis of libraries of fluorescent molecules is potentially useful for finding lead compounds in the development of novel functional fluorescent molecules. It should be possible to construct larger libraries by combinations of these methods with the introduction of diversity at various positions of the coumarin structure. Such libraries might well contain promising candidates for novel fluorescent sensors. 

Since the coumarin structure occupied fewer pockets than the pteptidomimetic analogs (Fig. 14) and the two binding modes in the crystal structure showed that the coumarin side chain could occupy two separate binding sites, the concept of branching the phenoxy side chain was pursued. This resulted in 32, which incorporated a nitrogen at the branching point... 

About 80 lactones have been identified in tobacco smoke. These compounds, especially they-butyrolactones, andothers, have alkylating potential and some have been reported to be carcinogenic in laboratory animals [Lawley (6A12)]. [see also Appendix 2, pp. 387-394) in (1870)]. Quantitatively, about half the lactones in the smoke consist of y-butyrolactone [lARC (6A10)] (about 10 pg/cigarette) and its derivatives 5-valerolactone and some alkylated and unsaturated 5-valerolactones, as well as coumarin [see pp. 427-430 in Wynder and Hoffmann (4332)], 6-methylcoumarin, and 3,4-dihydrocoumarin have also been isolated [Schumacher et al. (3553)]. The occurrence of coumarin derivatives in smoke could be due to pyrolysis of polyphenols with a coumarin structure. .. or of plant extracts added to tobacco to enhance flavour [see pp. 427-430 in Wynder and Hoffmann (4332)]. Coumarin itself is carcinogenic to rats after oral administration [lARC (6A10)]. 

Many natural products contain the coumarin structure [28]. Aesculetin 15 is extracted from horse chestnuts and psoralen 16 from the Indian plant Psoralea corylifolia. Furocoumarins such as 16 are photochemically active. On UV irradiation, they induce processes in the cell which lead to an increase in skin pigmentation and inhibition of cell division. This is due to the formation of cyclobutane with the pyrimidine bases of nucleic acids. Psoralens are used in the treatment of psoriasis. 

To date, at least 1300 coumarins have been identified and many new coumarin structures are being reported each year [12,13]. A variety of methods have been developed for the identification of known and novel... 

Simple coumarins (lactones of phenylpropanoic acids with a 2//-l-benzopyran-2-one nucleus) are widespread in plants the four most widely distributed coumarins are coumarin (1), umbelliferone (2), esculetin (aesculetin) (3), and scopo-letin (4) (Fig. 9.1) (Brown, 1979). Coumarins have not been reported from algae or mosses, although umbelliferone has been reported from a liverwort (Berenbaum, 1991). Coumarin is both the name of a specific compound and the name of a group of structurally related compounds. Variations of these basic coumarin structures are encountered commonly (especially in the Apiaceae) and at least 300 simple coumarins and a total of at least 1000 naturally occurring coumarins are known (Berenbaum, 1991 Brown, 1986, personal communication). Many coumarins, such as xanthyletin (5) and seselin (6), are prenylated. 

In addition to relatively simple coumarins, a second group of more complex coumarins is known in which the coumarin structure is prenylated (i.e., a five-carbon unit derived from mevalonic acid metabolism is attached). The five-carbon mevalonate-derived unit of these compounds usually is re-... 

Schofield first described the sweet clover disease of cattle as a defect in blood clotting [2]. It has been shown since that this disease is connected with prothrombin deficiency [403, 404]. Later, the coumarin structure was recognised as the toxic agent of spoiled sweet clover hay responsible for the anticoagulant activity [34]. The bis-hydroxycoumarin (61) (dicoumarol) as the prototype of these compounds, was isolated from clover [33, 405] and applied in therapy [406-408]. 

Although predictions on the course of chemical progress can be widely off the mark, the main outlines of coumarin chemistry seem to be broadly established if one takes as a criterion, the new coumarin structures reported in the past decade. With the exception of a series of 3-substituted 4-hydroxy-5-methylcoumarins, probably biosynthesized from acetate and largely confined to the tribe Vernonieae (Compositae), most of the structures of new coumarins reported in this period are predictable variants of established structural patterns. Methods of coumarin isolation and structure determination are straightforward by modern standards. The literature contains a sizable data base of spectroscopic parameters making structure determination a fairly routine procedure. 

Tomimatsu, T., H. Hasegawa, and K. Tori Studies on the Chemical Components of the Rutaceae Plants — VII. Components of the Roots of Poncirus trifoliata Rafinesque (5). Poncitrin, a New Coumarin Structure and Chemical Degradation. Tetrahedron 30, 939 (1974). 

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. 

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