Glucuronide conjugates of Soraprazan (BY359), a new potassium-competitive acid blocker (P-CAB) for the treatment of acid-related diseases

Glucuronide conjugates of Soraprazan (BY359), a potent novel anti-secretory drug (currently in Phase II clinical trials), were not directly accessible synthetically. This was due to the relative instability of Soraprazan under the harsh Lewis acid conditions employed in popular glucuronidation methodologies and a lack of reactivity under alternative, Koenigs-Knorr, coupling conditions. We have now devised a successful synthesis using the novel N-acetylated Soraprazan to access the required glucuronide metabolites on gram scale. Coupling of this novel aglycone with methyl 1-O-trichloroacetimidoyl-2,3,5-tri-O-isobutyryl-α-d-glucopyran-uronate in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) gave the protected glucuronide intermediates. A one-pot two-step deprotection involving hydrolysis of the ester functionalities and removal of the N-acetyl group with alkaline hydrazine delivered the title compounds in satisfactory yield.