Balsalazide

It is usually administered as the disodium salt. Balsalazide is a prodrug of mesalazine, also known as 5-aminosalicylic acid, or 5-ASA. The advantage of balsalazide over mesalazine in the treatment of ulcerative colitis is believed to be due to balsalazide not being metabolized in the small intestine; it can thus reach the large intestine intact, where it is then metabolized to mesalazine. It is in the category of disease-modifying antirheumatic drugs (DMARDs) family of medications. It is unclear exactly how it works.

Synthesis

Ex 3 is actually for Ipsalazide. See Ex 4 for Balsalazide proper. Same protocol but uses β-Alanine.

1. Starting material is 4-aminohippuric acid, obtained by coupling para-aminobenzoic acid and glycine.
2. That product is then treated with nitrous acid to give the diazonium salt.
3. Reaction of this species with salicylic acid proceeds at the position para to the phenol to give balsalazide.