Fluorenylmethyloxycarbonyl protecting group
The other common method for introducing the Fmoc group is through 9-fluorenylmethylsuccinimidyl carbonate (Fmoc-OSu), which may itself be obtained by the reaction of Fmoc-Cl with the dicyclohexylammonium salt of N-hydroxysuccinimide.
It may be cleaved by bases, typically a solution of piperidine:
Because the fluorenyl group is highly fluorescent, certain UV-inactive compounds may be reacted to give the Fmoc derivatives, suitable for analysis by reversed phase HPLC. Analytical uses of Fmoc-Cl that do not use chromatography may be limited by the requirement that excess Fmoc-Cl be removed before an analysis of fluorescence.
Common amine protection methods
- Fluorenylmethyloxycarbonyl chloride or 9-fluorenylmethyloxycarbonyl azide (itself made by reacting Fmoc-Cl with sodium azide), sodium bicarbonate and aqueous dioxane
Common amine deprotection methods
- 20% Piperidine in dimethylformamide (Fmoc Group has an approximate half life of 6 seconds in this solution)
- Tetra-n-butylammonium fluoride in the presence of dimethylformamide
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- Farrera-Sinfreu, Josep; Royo, Miriam; Albericio, Fernando (2002-10-21). "Undesired removal of the Fmoc group by the free ε-amino function of a lysine residue". Tetrahedron Letters. 43 (43): 7813–7815. doi:10.1016/S0040-4039(02)01605-2.