Carbamic acid ester prodrugs hydrolysis

The potential of carbamic acid ester prodrugs (R-O-CO-NR R") is well-established by a number of studies on their stability and metabolism. Upon hydrolysis, they liberate the active agent ROH and the carbamic acid R R"N-COOH, which, being unstable, breaks down to the amine R R"NH and C02 (see also Sect. 8.7). The mechanism of HCT-catalyzed hydrolysis of carbamates, summarized in Fig. 8.7,b, is more complex than that of carbonates [153][158][159]. In the case of N,N-disubstituted carbamates (R-O-CO-NR R"), the only possible mechanism is as for carbonates (Fig. 8.7,b, Reaction a), which is, presumably, also the mechanism of enzyme-catalyzed hydrolysis for all carbamates. 

Fig. 8.18. Metabolic activation of the prodrug molsidomine (8.159), first by enzymatic hydrolysis of the carbamic acid ester moiety to the inactive metabolite 8.160, followed by spontaneous degradation to the active metabolite 8.161, most likely an NO donor [207] [208]...

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