Synthesis
FMOC-L-aspartic acid was prepared as follows:
Two milligrams of the amino acid derivative were weighed into a screw-cap glass vial (1 cm³) and 1 cm³ of HFIP. 0.1N (approximately 0.37% w/v) hydrochloric acid (10 μl of approximately 37% HCl aqueous solution) was added per 990 μl of HFIP. The solution was allowed to stand and then analyzed by RP-HPLC. Judging from the strong yellow appearance of the triphenylmethyl cation, the removal of the /V-Trt group from Fmoc-Asp(OtBu)-OH by 0.1N HCl in the HFIP was almost instantaneous. After 10 minutes of reaction, trace amounts of the starting material could not be identified by HPLC, yielding FMOC-L-aspartic acid.
