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0 °C

A 250 ml round bottom flask was charged with 4.190 g (0.0181 mol) of N-BOC-6-aminocaproic acid, 7, 4.60 g of 9-fluorenylmethyl carbazate (FMOC), (prepared by the method of Carpino et. al., 1972, J. Org. Chem., 37:3404) and 35 ml of N,N-dimethylformamide. The reaction solution was cooled to 0° C. and then 3.75 g (0.0182 mol) of 1,3-dicyclohexylcarbodiimide (Aldrich) was added. The reaction mixture was allowed to stir for 2 h at 0° C. The white precipitate which formed during this time was filtered off and the solvents evaporated under reduced pressure. The distillation residue was applied to a 225 cc pad of silica gel (Merck), which was then washed with 1L of chloroform. The product was then eluted from the column using 1L of 50% methanol in chloroform. The solvents were evaporated from the desired eluent fractions to give 4.98 g (0.011 mol, 59% yield) of N-BOC-6-aminocaproic acid, N'-FMOC hydrazide, 8, as a yellow oil. 1H NMR (DMSO-d6, TMS) showed the peaks observed in the starting material and new protons in the aromatic region between 7-8 ppm (FMOC group).

1. custom(prepared by the method of Carpino et. al., 1972, J
2. customThe white precipitate which formed during this time
3. filtrationwas filtered off
4. customthe solvents evaporated under reduced pressure
5. washwas then washed with 1L of chloroform
6. washThe product was then eluted from the column
7. customThe solvents were evaporated from the desired eluent fractions