Synthesis of terminally protected 9-amino-4,5-diazafluorene-9-carboxylic acid, the first rigid, transition-metal receptor, C-alpha,alpha-disubstituted glycine

N-tert-Butyloxycarbonyl-9-amino-4,5-diazafluorene-9-carboxylic acid methyl ester, Boc-Daf-OMe, the first C-alpha,C-alpha-disubstituted glycine containing a rigid bipyridine ligand in a totally controlled spatial situation relative to the C-alpha atom of the amino acid, and a potential building block for the synthesis of peptide supramolecular devices, has been synthesized by acylation of the anion of N-benzyl-4,5-diazafluorene-9-methylenamine, followed by N-protection. Hydrazinolysis of the ester function afforded the hydrazide Boc-Daf-NHNH2, a key precursor for the acylazide coupling method.