14 イソプレノイドキノン類の合成

抄録

I. Synthesis of 2,3-dialkoxy-5-alkyl-1,4-benzoquinone a) 4a and 4b obtained from 1 were oxidized with organic peracids to give 2,3-dimethoxy-(5a) and 2,3-diethoxy-5-methyl-1,4-benzoquinone (5b). b) 9a and 9b obtained from 6 were oxidized in a similar manner to give 5a and 10. II. Synthesis of isoprenoid quinones The authors found two new condensation methods. a) Method using an N-sulfinylamine. A solution of hydroquinone (12), methyl N-sulfinylanthranilate (14) and phytol (13) in dioxane was heated and oxidized with ferric chloride to give 2,3-dimethoxy-5-methyl-6-phytyl-1,4-benzoquinone (15) as well as by-products 16 and 17. The structures of 16 and 17 were made clear and the reaction mechanism was discussed. The results are shown in Table 1. b) Method using a metal. A solution of 5a and X-CH_2-CH=C-CH_3-CH_2-R in petroleum ether was treated with slightly an excess amount of amalgamated zinc at the room temperature to give 18. The product 18 was obtained also from hydroquinone (12). The reaction mechanism and the results are shown in Table 2. III. Stereochemistry of isoprenoid quinones It has been so far known that the steric configuration of the side chain of naturally occurring isoprenoid quinones is all-trans, but synthesized isoprenoid quinones inevitably contain a small amount of the cis-isomer. Then, the authors separated these isomers by the column chromatography to confirm their yields and to compare their NMR spectra with each other. The relationship between the structures of the quinones and the biological activity is also mentioned.