8- Nitro-7-hydroxycoumarin

Coumarins constitute a major class of widely distributed O-heterocyclic natural products isolated from citrus fruits and vegetables [52]. Naturally occurring coumarins possess a variety of biological activities, including antitumor activity [53]. 7-Hydroxycoumarin and 8-nitro-7-hydroxycoumarin were shown to be potent cytotoxic agents against the human renal cell carcinoma cell line. 

Regarding leukemia, the derivate 8-nitro-7-hydroxycoumarin can induce apoptosis of the human leukemic cell lines HL-60 and K562 through the alteration of cell cycle and inhibition of DNA synthesis [240]. Another derivate of coumarin called esculetin or 6,7-dihydroxycoumarin was also able to arrest the cell cycle of the HL-60 cells [241]. Thus, these coumarin derivates could be elected as potential candidates to use them as drugs with antiproliferative effects in leukemia patients. 

Essences and extracts of 9 plants as well as safrole, coumarin and hydroxycoumarin, thujone and pinocamphone are explicitly prohibited (Art. 1320). Also forbidden is the use of salicyl aldehyde, hydrocarbons, pyridine derivatives, nitro compounds and organic nitrites (Art. 1321). 

Reduction of the double bond in an olefinic aliphatic nitro derivatives is usually easy. The olefin linkage may be preserved only in aromatic nitro compounds [equation (j)] , or in particular structures such as hydroxycoumarins or pyranones . 

In general, the a SCS are similar to those of corresponding 1- and 2-substituted naphthalenes (20, 49, 70-72). There are only a few exceptions. For example, the a-methyl effect in 7-methyl-coumarin is considerably larger than for all other isomers (11.2 vs. 8.3-9.7 ppm) (20). Despite the similarity of the a-hydroxy effects in 4-hydroxycoumarin and 1-naphthol (22.4 and 23.4 ppm, respectively), the corresponding methoxy effects are quite different (22.6 and 27.6 ppm, respectively). In 6-cyano- and 7-nitrocoumarin the a SCS are smaller by ca. 3 ppm than in 2 cyano- and 2-nitro-naphthalene. Again, there is no satisfactory explanation. 

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