Solid-phase S-3CR generates N-substituted α-aminonitriles for the synthesis of α-phenyl-α-(1-piperazinyl) substituted amino acids

Structurally diverse amino acids were prepared as versatile synthons for combinatorial chemistry. Using an optimized solid-phase synthesis by Strecker-three-component-reaction (S-3CR), two different polymer linker constructs carrying piperazine were investigated. (a) Acrylate derived base-labile linker yielded α-aminonitriles with N-alkylated piperazines via Hofmann elimination after quarternisation with an alkyl halide. The crude product purities were in the range of 54–87%. (b) A urethane type linker yielded α-aminonitriles with the free piperazine nitrogen when cleaved with acid and the product purities were 72–93%. The α-aminonitriles were easily converted to novel Nɛ– Fmoc-protected α-amino acids with α-(1-piperazinyl) and α-phenyl substituents.Structurally diverse amino acids were prepared as versatile synthons for combinatorial chemistry. Using an optimized solid-phase synthesis by Strecker-three-component-reaction (S-3CR), two different polymer linker constructs carrying piperazine were investigated. (a) Acrylate derived base-labile linker yielded α-aminonitriles with N-alkylated piperazines via Hofmann elimination after quarternisation with an alkyl halide. The crude product purities were in the range of 54–87%. (b) A urethane type linker yielded α-aminonitriles with the free piperazine nitrogen when cleaved with acid and the product purities were 72–93%. The α-aminonitriles were easily converted to novel Nɛ– Fmoc-protected α-amino acids with α-(1-piperazinyl) and α-phenyl substituents.