However, dibucaine has sufficient lipid solubility for anesthetic activity, even though it is an amide. Reverse amides are active in the lidocaine series, but the ortho positions must be substituted to reduce hydrolysis of the amide. Replacement of the ester by a ketone, ether, thioether or sulfone results in analogues with little or no activity. Modifications of the Aromatic Ring Simple esters of benzoic acid, such as benzocaine, have low but discernable activity. Their activity increases as branched or straight chain alkylamino groups are added, or with branching of the intermediate chain.
Simple ketones have low activity unless the aromatic ring is substituted, as in dyclonine.