32 改良Mosher法の新展開 : 2級アルコール類の絶対配置の決定(ポスター発表の部)

概要

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We have reported on a convenient method, an advanced Mosher method, to elucidate the absolute configurations of secondary alcohols. This method was based on the analyses of the difference of the chemical shifts (^1H) between the (+) and (-)-MTPA esters of the alcohols. This method has been successfully applied to elucidation of the absolute configurations of marine diterpenes 1, 6-9. However, in the case of a marine triterpene, sipholenol-A (10a), this method could not be applied. The main reason of this anomaly is that the MTPA group occupies the sterically crowded axial position. This problem was surmounted by conversion of 10a into episipholenol-A (11a), in which the hydroxy group exists in sterically freer equatorial position. Application of this method to 11a led to elucidation of its absolute configuration as well as that of 10a shown in the respective structures. This result agreed with that determined by the X-ray crystallography of the (-)-MTPA ester of 10a. The influence of the steric hinderence on the conformation of the MTPA moiety, which is essential to the advanced Mosher method was studied by applying this method to the model compounds, 4, 12-14, the absolute configurations of which are known.
天然有機化合物討論会の論文
1990-09-25