Synthesis and biological identification of the acyl glucuronide of the antiinflammatory drug ML-3000

The synthesis and identification in biological samples of the 1-O-acyl glucuronide 6 of the anti-inflammatory drug ML-3000 is described. Starting with -glucuronic acid γ-lactone, 2,3,4,-tris(tert.-butyldimethysilyl) glucuronic acid trichloroethylester 4 was prepared (in seven steps) and subsequently coupled with 1 under Mitsunobu conditions. Deprotection, i. e. removal of the trichloroethoxy group with zinc dust and desilylation with hydrofluoric acid in acetonitrile afforded a mixture of α- and β-6 which could be separated by preparative HPLC. The abundance of 6 in bile and plasma samples obtained from animal studies with the cynomolgus monkey and the rabbit following repeated administration of 1 could be demonstrated by LC-electrospray MS analysis.