title: Synthesis, absolute configuration and biological activities of both enantiomers of 2-(5,7-Dichloro-3-indolyl)propionic acid: a novel dichloroindole auxin and antiauxin.
abstract: 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.
authors.affiliation: Cooperative Research Laboratory for Plant Growth Regulator Development, National Institute of Advanced Industrial Science and Technology, Moriyama-ku, Nagoya, Japan. m.katayama@aist.go.jp
authors.forename: Masato
authors.initials: M
authors.lastname: Katayama
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Kato
authors.forename: Shingo
authors.initials: S
authors.lastname: Marumo
mesh_terms: D018554:Avena / Q000187:drug effects; D018548:Cotyledon; D007210:Indoleacetic Acids / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008968:Molecular Conformation; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D007210:Indoleacetic Acids; D007211:Indoles