(a) Fmoc-AA-OH (3
equiv),
HCTU (3 equiv), DIPEA (6 equiv), in DMF 50 min; (b) 20% piperidine/DMF
(1 × 5 min, 1 × 10 min); (c) Alloc-Gly-OH (5 equiv), DIC
(5 equiv), DMAP (0.3 equiv) in DMF; (d) palladium tetrakis(triphenylphosphine)
(0.1 equiv), PhSiH3 (10 equiv), in DCM 40 min; (e) 10%
HFIP in DCM (1 × 30 min, 1 × 5 min); (f) DPPA, DIEA in DMF
6 h; (g) TFA:TIPS:DODT:H2O (92.5:2.5:2.5:2.5) 90 min. HPLC
and mass spectrum of peptides 1, 8, and 10. O-(1H-6-chlorobenzotriazole-1-yl)-1,1,3,3-tetramethyluronium
hexafluorophosphate (HCTU), 1,1,1,3,3,3-hexafluoro isopropanol (HFIP),
dichloromethane (DCM) diphenylphosphoryl azide (DPPA), di-isopropyl
carbodiimide (DIC), dimethylaminopyridine (DMAP), diisopropylethylamine
(DIEA), dimethylformamide (DMF), triisopropylsilane (TIPS), 3,6-dioxa-1,8-octanedithiol
(DODT), and trifluoroacetic acid (TFA).