Katayama Masato, Kato Yasuhito, Marumo Shingo
Cooperative Research Laboratory for Plant Growth Regulator Development, National Institute of Advanced Industrial Science and Technology, Moriyama-ku, Nagoya, Japan.
Biosci Biotechnol Biochem. 2004 Jun;68(6):1287-92. doi: 10.1271/bbb.68.1287.
Racemic 2-(5,7-dichloro-3-indolyl)propionic acid (5,7-Cl(2)-2-IPA) was synthesized from 5,7-dichloroindole-3-acetic acid by successive esterification, methoxycarbonylation, methylation, and double hydrolysis. The racemate was converted to diastereomeric esters of l-menthol; these were separated by recycling HPLC into two optically active diastereomers that were then hydrolyzed with p-TsOH to two optically active enantiomers of 5,7-Cl(2)-2-IPA. The absolute configurations of both these enantiomers were determined by comparing the (1)H-NMR spectra of their diastereomeric l-menthyl esters with those of the diastereomeric l-menthyl esters of 2-(3-indolyl)propionic acid (2-IPA) of known absolute configurations.An assay by the coleoptile elongation of Avena sativa showed the (S)-(+)-enantiomer of 5,7-Cl(2)-2-IPA to have weak auxin activity, whereas the (R)-(-)-antipode had no auxin activity at any concentration tested. Interestingly, the (R)-(-)-enantiomer had antiauxin activity very close to that of 2-(5,7-dichloro-3-indolyl)isobutyric acid (5,7-Cl(2)-IIBA), a strong antiauxin. These data indicate that, of the two methyl groups in its molecule, the antiauxin activity of 5,7-Cl(2)-IIBA was due only to the (R)-methyl group.
外消旋2-(5,7-二氯-3-吲哚基)丙酸(5,7-Cl(2)-2-IPA)由5,7-二氯吲哚-3-乙酸经连续酯化、甲氧基羰基化、甲基化和双水解反应合成。外消旋体转化为L-薄荷醇的非对映体酯；通过循环高效液相色谱法将它们分离为两种旋光活性的非对映体，然后用对甲苯磺酸将其水解为5,7-Cl(2)-2-IPA的两种旋光活性对映体。通过比较它们的非对映体L-薄荷醇酯与已知绝对构型的2-(3-吲哚基)丙酸(2-IPA)的非对映体L-薄荷醇酯的(1)H-NMR光谱，确定了这两种对映体的绝对构型。通过燕麦胚芽鞘伸长试验测定，5,7-Cl(2)-2-IPA的(S)-(+)-对映体具有较弱的生长素活性，而(R)-(-)-对映体在任何测试浓度下均无生长素活性。有趣的是，(R)-(-)-对映体的抗生长素活性与强抗生长素2-(5,7-二氯-3-吲哚基)异丁酸(5,7-Cl(2)-IIBA)非常接近。这些数据表明，在其分子中的两个甲基中，5,7-Cl(2)-IIBA的抗生长素活性仅归因于(R)-甲基。
