Efficient synthesis of hydrocarbon-bridged diaminodiacids through nickel-catalyzed reductive cross-coupling

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Solid-phase incorporation of pre-prepared diaminodiacids has been established as an efficient strategy for the chemical synthesis of peptide disulfide bond mimics. Hydrocarbon-bridged diaminodiacids represent one important category of diaminodiacids but they remain difficult to synthesize. In the present work, we reported the use of newly-developed nickel catalyzed reductive cross-coupling reaction to efficiently synthesize diaminodiacids with hydrocarbon bridges. Through optimization of the reaction conditions, the yield of the hydrocarbon bridge formation reached about 50%, even when the reaction was scaled up to the gram level. Subsequently, using our recently developed Dmab/ivDde protecting group system, we obtained a new hydrocarbon-bridged diaminodiacid that are suitable for metal-free deprotection conditions. We demonstrated the utility of this Dmab/ivDde protected hydrocarbon-bridged diaminodiacid in the synthesis of a disulfide surrogate of oxytocin.