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Lys(Boc)-Pra-Asn(Trt)-Thr(tBu)-Ala-Thr(tBu)-Ala(N3)-Ala-Pal-PEG resin (16) (0.498 g, 0.09 mmol) was cleaved with TFA/iPr3SiH/H2O (v/v/v; 95/2.5/2.5, 5.0 mL) for 2 h, peptide was isolated as described in the general section to afford 47.3 mg of crude peptide 17. The crude peptide 17 (16.3 mg) was purified by RP-HPLC on a preparative Phenomenex Gemini C18, column at a flow rate of 5 mL min-1, using a linear gradient of 1percentB to 61percentB over 60 min (ca. 1percentB per minute) and lyophilised to give the title compound 17 as a white amorphous solid (4.9 mg, 18percent).