INTRAMOLECULAR REMOTE FUNCTIONALIZATION OF STEROIDS BY BENZOPHENONE - INCREASED SPECIFICITY BY SOLVENT-INDUCED HYDROPHOBIC INTERACTIONS

Proximity of reactant sites is one of the major factors that contributes to specificity and high reaction rates observed in enzyme catalysis. Enzymes achieve this proximity between the reactant sites by having high affinity for the substrate. Structural studies on enzyme-substrate complexes provide sufficient evidence in this context and indicate that weak bonding interaction are involved in formation of such complexes. We have exploited the hydrophobic interaction between cholesterol and benzophenone to carry out photoinduced remote functionalisation of cholesterol at specific sites. Thus, using polar solvents intramolecular hydrophobic interaction between cholesterol and benzophenone permitted exclusive functionalisation of ring D in cholesterol. The current study indicates that weak interactions between the reactants can be used to bring them in proximity and photochemical reactions can provide the method for functionalising even inert sites like C-H bonds.