A molecular graphics study of factors influencing herbicidal activity of oximes of 3‐acyl‐tetrahydro‐2H‐pyran‐2,4‐diones

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Abstract
Structure‐activity relationships in oximes of a series of sixteen 3‐acyltetrahydro‐2H‐pyran‐2,4‐diones, exhibiting a variety of pre‐ and postemergent herbicidal activities, have been studied by means of computer graphics methods. The most active compounds are potent grass‐killers. This graminicidal activity appears to depend strongly on the size and shape of the substituent at the 6‐position of the pyran. The activity correlates with both molar refractivity and fit to a hypothetical ‘receptor’ probably the active site of acetyl coenzyme A carboxylase. The herbicide sethoxydim and the pyrandione herbicides appear to mimic the transition state of the reaction catalyzed by acetyl‐CoA carboxylase.The study has yielded a receptor model which defines clearly the three‐dimensional binding reguirements of the pyran ring and the substituents at the 6 position. It is not capable of providing information on the structural requirements of the 3‐acyl moiety. The model is capable of discriminating between active and inactive herbicidal compounds and provides a basis for the design of new herbicidal compounds with enhanced graminicidal activity.