In the hydrolytic degradation of salicylate-based poly(anhydride-esters), the monomer precursor or diacid is produced, which further breaks down into salicylic acid and a carboxylic acid. Current protocol for the preparation of a diacid, the monomer precursor, involves coupling of two salicylate molecules with an acyl chloride in the presence of a base (pyridine). This method requires an acyl chloride, which is synthesized when not commercially available.
This work investigates a new synthetic pathway to prepare salicylate-based diacids directly from dicarboxylic acids. This approach eliminates the need to prepare the acyl chloride, thereby reducing the overall number of steps. The new method involves the formation of a reactive intermediate in situ, which is produced when the dicarboxylic acid reacts with dicyclohexylcarbodiimide (DCC) and dimethylaminopyridine (DMAP). The reactive intermediate reacts with the free phenolate in a single step to yield the desired monomer precursor.
By exploring an alternate synthetic method to prepare salicylate-based diacids, the coupling capabilities of salicylates and carboxylic acids are broadened. Therefore, a wider range of salicylate-based poly(anhydride-esters) can be obtained for drug delivery applications.
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