Stable cyclopropene-containing analogs of the amino acid neurotransmitter glutamate

As a neurotransmitter, the amino acid glutamate has been the subject of efforts to generate structural analogs with unique properties. Here we report a practical, half-gram synthesis of two cyclopropene-containing glutamate analogs. These analogs are stable in solution, in the presence of the biological nucleophile glutathione, upon concentration, and during long-term storage, while maintaining their amenability to photo- or enzyme-caging and reactivity with bioorthogonal reaction partners like s-tetrazine or light-activated tetrazoles.