(+/-)-1-[(1R*,2R*,8aS*)-1,2,3,5,6,7,5,8a-Octahydro-1,2,8,8-tetramethylnaphthalen-2-yl]ethan-1-one (5) was identified as a minor (ca. 5%) but very powerful (5 pg/l (air)) constituent of the important perfumery synthetic Iso E Super(R). Its structure was assigned by NMR spectroscopy and established by a stereoselective synthesis starting from alpha-ionone (10). Diastereoselective conjugate addition of Me2CuLi to 10 was followed by a haloform reaction, esterification, and isomerization of the C=C bond by treatment with NaOCl (Schemes 3 and 4). The resulting allyl chloride 17 was ozonized and transformed into the trimethyl(vinyl)octahydrocoumarin 20 by diastereoselective Grignard reaction with ethynylmagnesium chloride, and subsequent Lindlar hydrogenation. Ireland-Claisen rearrangement of 20 followed by methylation with MeLi afforded the target molecule 5 that was identical with the material isolated from commercial Iso E Super(R).
(+/-)-1-[(1R*,2R*,8aS*)-1,2,3,5,6,7,5,8a-八氢-1,2,8,8-
四甲基萘烷-2-基]
乙烷-1-酮(5)被鉴定为重要
香料合成物 Iso E Super(R) 中的一种次要(约5%)但极其高效(5 pg/l(空气))的成分。其结构通过核磁共振(NMR)光谱学确定,并通过从 α-离子酮(10)出发的立体选择性合成得到验证。通过对10进行 Me2CuLi 的对映选择性共轭加成,随后进行 haloform 反应、酯化以及通过 NaOCl 处理的 C=C 键异构化(方案3和4)。所得的烯丙基
氯 17 经
臭氧分解,并通过与
乙炔基
镁氯化物的对映选择性 Grignard 反应以及随后的 Lindlar 氢化,转化为三甲基(
乙烯基)八氢
香豆素20。通过对20进行 Ireland-Claisen 重排,随后用 MeLi 甲基化,得到目标分子5,其与从商业 Iso E Super(R) 中分离的物质相同。