14 遠隔位不斉識別法の開発とその天然有機化合物の絶対配置決定への応用(口頭発表の部)

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Recently, we have developed a highly sensitive fluorescent derivatization reagent, 2-(anthracene-2,3-dicarboximido)ethyl trifluoromethanesulfonate (AE-OTf), for carboxylic acids. The reagent made it possible to detect fatty acids at sub-fmol levels. The ^1H-NMR studies on some AE-O-esters indicate that these compounds take the bent conformation as shown in Fig.1. Since some proton signals of the hydrocarbon chain were shifted to higher field, those protons would be located over the anthracene ring. Therefore, it can be expected that the chiral carboxylic acids having chiral centers at a remote position from their carboxyl groups should be descriminated by labeling with chiral AE-OTf analogues. Here, we report the preparation of chiral AE-OTf analogues 1-7 (Fig.3) and the results of the discrimination of their diastereomeric derivatives of some branched fatty acids 8-28 (Fig.4) on a reversed phase HPLC and ^1H-NMR. The branched fatty acid derivatives were separeated on an ODS column eluted with acetonitrile/ methanol/water or acetonitrile/methanol/n-hexane below 0O℃. In general, lower the column temperature is, better separation was obtained. Among seven reagents tested, 1-(2,3-anthracenedic arboximido)-2-propanol (2) and trans-2-(2,3-anthracenedicarboximido)-1-cyclohexa-nol (3) showed excellent separation ability. All chiral branched acids except 7-methylnonanoic acid (13) was separated into two peaks by labelling with trans-2-(2,3-anthracenedicarboximido)-1-cyclohexa nol (3), while 13 could be separated by labelling with 1-(2,3-anthracenedicarboximido)-2-propanol (2). These results allow us to determine the absolute comfiguration of chiral branched acids which have chiral centers remote from the carboxyl group up to 11 bond distances at fmol levels by derivatizing with these reagents. With respected to elution order of (S) and (R) isomers, there was a rule that (S) isomers chiral center was located at an even number position were eluted faster than (R) isomer when labelled with (S) or (S,S) configurated reagents, while (R) isomer were eluted fasterwith those having at odd number position. The branched methyl groups of 2-(2,3-anthracenedicarboximido)-1-propanol (1) derivatives gave different chemical shifts on 1H-NMR measured in CDCl_3. This meant that it was also possible to discriminate their chirality on 1H-NMR. It was also possible to discriminate theenantiomers of 12-methylpentadecanoic acid, which would be possible to bederived from a ceramide isolated from a marine plankton.
天然有機化合物討論会の論文
1998-08-31

14 遠隔位不斉識別法の開発とその天然有機化合物の絶対配置決定への応用(口頭発表の部)

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