L-Phenylalanine → Phenylalanine amide

Participants

Reaction Steps

Fmoc-Phe-OPfp (0.5 mmol) and HOBt (0.5 mmol) were added to a suspension of resin B (prepared from 185 mg, 0.1 mmol of the Fmoc-derivative) in DMF (5 ml) and the mixture was shaken for 1 hour. The resin was successively washed with DMF (5 ml×5), then treated with 20% piperidine in DMF (5ml) for 15 min. The treated resin was washed with DMF (5 ml×5) and CH2Cl2 (5 ml×5) and dried in vacuo; yield 179 mg. The dried resin (5 mg) was treated with 1 M thioanisole/TFA-m-cresole (100 μl-10 μl) at 28° C. for 60 min. H-Phe-NH2 liberated was determined by TLC scanner. The latter treated resin was subjected to 6N HCl hydrolysis. No Phe was detected by amino acid analyser. This result shows that phenylalanine had been cleaved almost completely from the resin. It was therefore established that resin B is useful as an amide precursor for amino acids and that the thioanisole-containing solution described above is a superior cleavage reagent.

Provenance & Evidence