Retro ACP Polystyrene vs ChemMatrix

Retro ACP Polystyrene

ChemMatrix

BACUMA Polystyrene vs ChemMatrix

BACUMA Polystyrene

ChemMatrix

Protocol:

The synthesis was made using aminomethyl ChemMatrix resin (0.1 mmol, 0.4 mmol/g).
The linker was coupled manually using Fmoc-Rink linker (3 equiv), PyBop (3 equiv), HOAt (3 equiv), and DIEA (9 equiv) in DMF.
Before Fmoc removal, an acetylation step was performed to block any possible free amino group.
The first amino acid was coupled manually, using HCTU (3 equiv), HOAt (3 equiv) and DIEA.
The rest of the synthesis was carried out on the synthesizer, using 4 equivalents of Fmoc protected amino acids, and HCTU (4 equiv) and DIEA (12 equiv) as the coupling system.
Before cleavage, the resin was acetylated [Ac₂O-DIEA-DMF (10:5:85)] for 70 min. Cleavage was carried out using TFA-TIS-H₂O (95:2.5:2.5) for 90 minutes.
The peptide was characterized by analytical HPLC (Rt = 12.9 min, 52.33%) and by HPLC/MS and MALDI-TOF (m/z calcd for C₂₀₃H₃₂₄N₅₀O₅₃S₃, 4405.35; found, 4406.72 [M + H]+).

Reference:
Albericio et al. J. Comb. Chem. 2006, 8, 213-220 and references cited therein.

H-(Ala)₁₀-Val-OH Polystyrene vs ChemMatrix

H-(Ala)₁₀-Val-OH Polystyrene

ChemMatrix

Poly Arg (21) Polystyrene vs ChemMatrix

Poly Arg (21) Polystyrene

ChemMatrix

Protocol:

The synthesis was carried out using aminomethyl ChemMatrix resin (0.22g, 0.45 mmol/g) having been previously incorporated with Fmoc-Rink AM linker using HOBt and DIPCDI (3 equiv) in DMF.
Peptide chain elongation was carried out on an automatic synthesizer, using TBTU as coupling reagent in presence of HOBt.
Cleavage was performed by treatment with TFA-TIS-H₂O (95:2.5:2.5) for 3 h to ensure complete removal of various Pbf protecting groups.
Characterization was made using HPLC (Rt = 7.80 min, 68%) and by HPLC/MS (m/z calcd for C₃₅H₆₃N₁₃O₁₀, 2590.42; found, 1297.1 [M + H]+/2, 865.1, [M + H]+/3, 649.1) [M + H]+/4, 519.6 [M + H]+/5.

Reference:
Albericio et al. J. Comb. Chem. 2006, 8, 213-220 and references cited therein.

B-amyloid 1-42 ChemMatrix

Protocol:

The synthesis was carried out automatically except for the incorporation of both the linker and the first amino acid, which were coupled manually on ChemMatrix resin (0.12 g, 0.58 mmol/g).
AB linker was incorporated with HBTU-HOBt-DIEA-DMF (3:3:3:9) for 90 minutes.
The first amino acid was coupled to handle by formation of an ester bond by means of Fmoc-L-Ala-OH-DIPCDI-HOAt-DMAP (5:5:5:0.5) in CH₂Cl₂ overnight at room temperature.
The 4(4-nitrobenzyl) pyridine test for alcohol determination indicated free hydroxyl group were still present, and a 2 h recoupling step was necessary.
Next, acetylation of the N-terminal group was carried out using Ac₂O-DIEA (50 equiv each) in DMF for 15 minutes.
The rest of the chain assembly was carried out automatically. Cleavage was performed with TFA-TIS-H₂O-EDT (95:2:2:1) for 90 min.
After lyophilization, a modification of the disaggregating protocol developed by Zagorski et al was applied. This method consists of a first stage in which the peptide is dissolved in neat TFA to obtain the monomeric form. In a second stage, the acid is removed by evaporation, dissolved in HFIP so as to maintain the peptide as a monomer, and evaporated.
This last step was repeated twice more, and an aliquot dissolved in HFIP was injected into the HPLC.
Characterization by HPLC (Rt = 9.33 min, 91%) and by MALDI-TOF (m/z calcd for C₂₀₃H₃₁₂N55O₆₀S₁, 4512.28; found, 4513.50 [M + H]+).

Reference:
Albericio et al. J. Comb. Chem. 2006, 8, 213-220 and references cited therein.