The water soluble steroid 1 acts as a catalyst for the enolization of the ketones 2a-c. The rate enhancement for 1-catalyzed reaction relative to imidazole-catalyzed reaction (R), increases as the size of the aromatic ring system of the substrate increases; a plot of log Rvs π has a slope of 0.43. This is interpreted in terms of hydrophobic binding between steroid α-surface and aromatic ring system which lowers the free energy level of the transition state for steroid-catalyzed enolization.
水溶性类固醇1作为酮2a-c的烯醇化催化剂。相对于咪唑催化反应(R),1催化的反应速率增强随着底物芳香环系统的大小增加而增加;log Rvs π的图表具有斜率为0.43。这被解释为类固醇α表面与芳香环系统之间的疏水结合,降低了类固醇催化的烯醇化过渡态的自由能水平。