Fig. 1. Synthesis of a difficult peptide sequence from influenza virus Hemagglutinin.¹¹ Analytical HPLC traces of crude product prepared using: (A) conventional automated SPPS, (a = target peptide, b = deletion of Met¹-Glu²-Asp³, c = deletion of Met¹-Glu², d = deletion of Glu¹, e = t-butylated product). (B) Conventional automated SPPS with backbone protection at Ala⁹. (C) Automated microwave assisted SPPS. (D) Automated microwave-assisted SPPS backbone protection at Ala⁹. (E) MALDI-MS of target peptide, a, (calculated mass [M + H]⁺ = 1481.6 m/z) peptide cleavage conditions: TFA/TMSBr/thioanisole/ethanedithiol (1.0 : 0.05 : 0.05 : 0.025 v/v), 1.0 h. HPLC conditions: RP-C18, 0–50% (0.1% TFA, 90% CH₃CN) in 30 min, 1 mL min^–1.