Scheme 1. (A) Hyperpolarization via SABRE and (B) hyperpolarization via SABRE-RELAY.

SABRE is used to hyperpolarize the transfer agent NH₂R, where R is H or CH₂Ph or CH₂CH₂Ph (etc.), which relays polarization to the analyte (HR″, route A), and R″ is amide, carboxyl, phosphate, or alkoxide (etc.). This process involves both proton exchange and spin-spin interactions and may be mediated by an intermediary HOR′, where R′ is H or suitable scaffold (route B). Center: Reaction scheme shows the formation of SABRE active 2-NH₃, which leads to NH₃.