Convenient syntheses of the in vivo carbohydrate metabolites of mycophenolic acid: reactivity of the acyl glucuronide

Following in vivo use of mycophenolic acid, the O-aryl and O-acyl glucuronides, as well as the recently discovered O-aryl glucoside (Scheme 1), are all found as metabolites. We describe convenient preparations of all three derivatives. The phenolic glycosides are obtained by phase-transfer-catalysed alkylation of methyl mycophenolate in very high yield, as an excellent alternative to the Kِnigs-Knorr reaction. We carefully optimised our earlier synthesis of the acyl glucuronide to give a highly pure product in a much improved yield. Finally, we describe the value of a synthetic acyl glucuronide in demonstrating its reactivity towards a known target protein with superior response to the naturally obtained material.