Synthesis of self-immolative glucuronide-based prodrugs of a phenol mustard

The design and synthesis of the mustard pro-prodrugs which can be used in A DEPT is reported. Prodrugs 1 and 2 include a glucuronide group which is con nected to the drug via an aromatic and/or aliphatic bis-carbamate spacer. T he design of these new prodrugs takes advantage of a spontaneous 1,6-elimin ation and/or an intramolecular cyclization reaction after enzymatic cleavag e. Thus, enzymatic-catalyzed hydrolysis of the glucuronyl moiety of 1 by Es cherichia coli beta-glucuronidase results in the liberation of the parent m ustard drug 20 with formation of CO2, 2-nitro-4-hydroxymethylphenol 19 and dimethylimidazolidinone 21. Surprisingly, prodrug 2 was not cleaved under t he same conditions. According to in vitro experiments, prodrugs 1 and 2 wer e similar to 50- and 80-fold less cytotoxic than the parent drug and, when treated with beta-glucuronidase, the level of cytotoxic activity of 1 becam e comparable to that of the drug. Stability of 1 in phosphate buffer was sa tisfactory. These results demonstrate that 1 is a prodrug that can be speci fically activated to release the cytotoxic agent.