The resin was washed with
DCM (three times) and DMF (three times) and then allowed to swell
in DMF for 30 min. After draining the DMF solution out, a DMF
solution of the mixture of Fmoc-protected amino acid (0.6 equiv
relative to resin loading) and DiEA (3 equiv) was added to the resin
and shaken for 30 min at room temperature.