| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
Chiral ketones are versatile intermediates of natural products and seen in the structure of biologically active compounds such as terpenes, pheromones, and so on. However, few studies are found in the literature for the direct method to determine the absolute configurations of these chiral ketones. X-Ray crystallographic analysis is the only method to determine the absolute configuration of a molecule. The anomalous dispersion effect of a heavy atom must be used for the determination of the absolute configuration. Hydrazines are well-known to be good crystalline agents for ketones. Thus, a phenylhydrazine derivative having a halogen atom is employed as a crystalline agent. We designed and synthesized some hydrazines as crystalline agents, and found that 2-chloro-4,6-dinitrophenyihydrazine is the useful crystalline agent for various chiral ketones. 2-Chooro-4,6-dinitroaniline is a weak base because of two nitro groups and a chlorine atom, so that diazotization does not occur with a conv
… More
entional way. Therefore, the aniline dissolved in hot acetic add was diazotized with nitrosyl sulfate prepared from sodium nitrite and sulfuric acid, and iodinated with potassium iodide to afford 1-chloro-2-iodo-3,5-dinitrobenzene. It was stirred with hydrazine monohydrate in methanol at room temperature to give the desired hydrazine. The reaction of the hydrazine and a chiral ketone gave the single crystal suitable for X-ray crystallographic analysis. The crystal structure and absolute configuration of the corresponding hydrazone was determined using the anomalous dispersion effect of a chlorine atom. The absolute configurations were successfully determined by Flack parameter and intensities comparison of Bijvoet pairs. This is the simple and direct method and the potential of this methodology was clearly demonstrated. 2-Chloro-4,6-dinitrophenylhdrazine is a useful crystalline agent for the absolute configuration determination. This method can be applied to terpenes and pheromones, and is helpful for the determination of the absolute configuration of various chiral ketones. Less
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