36
Setting up a Synthesis
Special Case: Hyper Acid Sensitive Resins (e.g. 2-chlorotrityl)
Acidic additives (HOBt, HOAt, Oxyma) can lead to premature cleavage of the peptide from the resin (low yields).
Activation methods containing DIEA are more basic and thus preferred to DIC/Oxyma for these resins at high
temperatures. Since lower temperatures should be used, the more aggressive HATU activator is recommended.
CEM Corporation offers Cl-TCP(Cl) ProTide which shows excellent stability to high temperatures and acidic additives
such as Oxyma Pure, yet still exhibits hyper-acid sensitivity. The Cl-TCP(Cl) ProTide resin can be cleaved under 1%
TFA/DCM conditions.
CEM Preference Reagents Resin/Linker Coupling Microwave Method
1
Exceptions
1 AA/DIC/Oxyma
2
in DMF
Cl-TCP(Cl) ProTide Resin Standard Coupling (90°C 2 min) N/A
3
2-Chlorotrityl resin 60°C 5 min Coupling
4
N/A
3
2 AA/HBTU/DIEA
5
in DMF
Cl-TCP(Cl) ProTide Resin 75°C 5 min Coupling Cys/His: 50°C 10 min Coupling
2-Chlorotrityl resin 50°C 10 min Coupling N/A
1
Standard deprotection (90°C 1 min) can be performed in all cases.
2
0.1 equivalents DIEA should be added to Oxyma solution
3
Recommended Coupling Microwave Method assumes employment of His(Boc). For other His derivatives, use 50°C 10 min Coupling
Microwave Method.
4
Coupling time can be extended to 10 min.
5
DIEA should be prepared in NMP.
NOTE
The rapid microwave methods used by the Liberty Blue employ rapid heating rates. For both the
deprotection and coupling methods the set temperature of 90 °C should be reached within 20-30 seconds,
and maintained for at least 45 seconds and 100 seconds respectively. The starting temperature for each
reaction will be signicantly warmer than room temperature as residual heat will remain from the previous
reaction.
Preparing Reagents
WARNING
Handle all chemicals under a fume hood, and wear suitable protective clothing such as safety glasses,
chemical resistant gloves, and a laboratory coat. Dispose of all waste in accordance with all applicable
local, state, and federal health and safety recommendations. For detailed information on the safety
requirements for the chemicals used on the Liberty Blue, refer to the appropriate SDS documents.
Preparing Activator Solution
1. Weigh out the appropriate amount of activator (as calculated using the Usage and Reagent Calculators) and
transfer to a 250 mL glass bottle.
2. Add the appropriate volume of solvent.
3. Put a cap on the bottle. Gently swirl the bottle to ensure that all of the activator has gone into solution.
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