(R)-1-Boc-3-methylpiperazine (S)-Piperazine-2-carboxylic acid (S)-1-Boc-3-hydroxymethyl-piperazine 1-Boc-3-hydroxymethyl-piperazine 3-[[(1,1-Dimethylethoxy)carbonyl]amino]-L-alanine methyl ester (R)-N-Boc-piperazine-2-carboxylic acid methyl ester (S)-1-N-Boc-piperazine-2-carboxylic acid methyl ester Methyl 4-Boc-piperazine-2-carboxylate (S)-4-N-Boc-piperazine-2-carboxylic acid