N-Silylation of Drugs

This behaviour was observed with testosteroxy-trimethylsilane (lb) in biological experiments33. The androgenic and myotropic activities of testosterone (la) and its silyl derivative lb were estimated by a routine assay (21-day-old castrated male rats s.c. injection once a day for 7 days autopsies the day after the last injection). The silyl compound lb was more active than testosterone itself. This observation may reflect rapid transport of the silicon compound across the lipid barrier and rapid cleavage to testosterone. 

Lukevics reports34 that silylation of 2-dibutylaminoethanol (2a) enhances its insect-repellent activity against X. cheopis (Table 3). For silyl derivative 2c the coefficient of repellent action reaches 99% at a dose of 5 g/m2. This effect is accompanied by prolongation of the repellent action. According to Lukevics, the activity of silyl derivatives 2b-2e cannot be explained by hydrolysis alone, because this process forms less active compounds. It appears that the repellent properties are concentrated within the molecule of the organosilicon compound itself. 

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