[24] Caged probes for studying cellular physiology: Application of o-Nitromandelyloxycarbonyl (Nmoc) caging method to glutamate and a Ca2+-ATPase inhibitor

Publisher Summary This chapter focuses on a newly developed caging group, two caged molecules based upon them, and biological applications of these two new caged reagents. The newly introduced photosensitive o-nitromandelyloxycarbonyl (Nmoc) caging group offers several advantages. First, flash photolysis of Nmoc-caged species releases bioeffector molecules on the millisecond time scale, with quantum yields of ∼0.1. Second, the Nmoc cage is synthesized with relative ease. Third, Nmoc-imidazole, a chemically activated form of the Nmoc cage, reacts smoothly with hydroxyl and amino groups to form, respectively, carbonate and carbamate linkages that are highly resistant to spontaneous cleavage in the absence of light. These characteristics combine to make Nmoc an attractive caging group for biomolecules bearing hydroxyl or amino groups. The chapter describes preparative procedures and synthetic procedures for methyl Nmoc-imidazole. The active caging reagent, Nmoc-imidazole, is prepared in two versions: the methyl and tert-butyl ester forms. For caging hydroxyl groups in biomolecules, the methyl ester form of Nmoc-imidazole is quite satisfactory.