Design, synthesis and photochemical properties of caged bile acids.

Photolabile derivatives of bile acids (8-10 and 13) were synthesized via silver (I) oxide promoted selective etherification of 3alpha-hydroxyls. Quantitative production of the parent cholic acid was detected from the photolytic mixture of 3-NB-CA (8) in Tris buffered solution. Interestingly, the unexpectedly stable nitroso-hemiacetal intermediate (14) was detected when the photolysis was conducted in methanol. The enzymatic analysis using 7alpha-HSDH showed 8 and 9 could serve as caged bile acids that might be able to regulate certain biological processes upon UV irradiation.