COMPARATIVE AB INITIO SCF CONFORMATIONAL STUDY OF 4-CHLORO-INDOLE-3-ACETIC ACID AND INDOLE-3-ACETIC ACID PHYTOHORMONES (AUXINS)

摘要

An ab initio conformational analysis of 4-chloroindole-3-acetic acid was performed at the RHF/6-311G** level. The mirror symmetrical conformer (in which the indole ring is coplanar with the COOH group) is most stable; next in energy are the two conformers with the C-COOH fragment perpendicular to the indole ring with relative energies of 2.72 and 6.69 kJ/mol. H ... Cl hydrogen bonding results in only a minor stabilization. The results are combined with those obtained earlier for indole-3-acetic acid and recent biological data regarding auxin (growth hormone) activity. From this, assumptions concerning the biologically active conformation are drawn. (C) 1996 John Wiley & Sons, Inc. [References: 28]