A caged sperm‐activating peptide that has a photocleavable protecting group on the backbone amide

摘要

>A backbone-caged sperm-activating peptide (caged speract) that has a 2-nitrobenzyl group at a backbone amide and a vastly reduced affinity for its receptor (IC₅₀=950 nM) was synthesized. UV irradiation of caged speract photocleaves the 2-nitrobenzyl group (τ _1/2=26 μs), restoring its affinity (IC₅₀=0.67 nM) and ability to increase sperm intracellular pH and Ca2+, as intact speract. Backbone caging of the biological activity was more efficient than side chain caging, which adds a nitrobenzyl group on the peptide side chain. The backbone caging strategy described can be used as a general procedure to cage biologically active peptides, which have no side chain for introduction of a caging group.