AbstractUsing a set of representative members selected from 4‐pyridone‐3‐carboxanilides andortho‐chlorinated diphenyl ethers exhibiting light‐dependent herbicidal activity, we examined the three‐dimensional structure‐activity relationships quantitatively. The most stable conformation of each compound, regarded as the ‘active conformation’, was determined by either semi‐empirical orab initiomolecular orbital calculations. With a hypothesis defining a common substructural skeleton between the two different compound series. each molecule was superimposed. We first analysed the structure‐activity relationship using an index for the substructure shape similarity according to the superimposed conformations. After finding the relevance of the hypothesis, we examined the three‐dimensional structure‐activity relationship using the comparative molecular field analysis procedure. The results suggested that the two different series of compounds have a common region of the receptor site. The variations in the light‐dependent herbicidal potency were governed by hydrophobicty and three‐dimensional steric and electronic field parameters of molecules participating in the transport process and the interaction with the receptor site. The result was consistent with that derived from our previous quantitative analysis with the use of free‐energy‐related substituent parameters and the traditional regression procedure for a large
展开▼
