Microwave Method Parameters
Standard Deprotection
Stage
Temp (
o
C)
Power (W)
Time (sec)
Delta T
1
75
155
15
2
2
90
50
50
1
Standard Coupling
Stage
Temp (
o
C)
Power (W)
Time (sec)
Delta T
1
75
170
15
2
2
90
50
110
1
Microwave Power
Specific power settings will vary, depending on scale and the individual microwave. 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 temperature should not exceed 95 °C. If this occurs, then the power for the stage
where the overage occurred should be decreased.
The power setting can be changed in the Microwave Editor, which can be accessed from the Edit menu. Power settings
can be changed “on-the-fly”, meaning that changes made in the Microwave Editor during a run will be applied on the next
microwave step. The Run History file records the temperature during each microwave step and should be reviewed
periodically.
Special Coupling Cycles
DIC/Oxyma (or HOBt) Activation
Histidine
His(Boc) suppresses epimerization at elevated temperature, and by default, is coupled using the standard coupling
microwave method. His(Trt) is susceptible to epimerization at elevated temperature. His(Trt) should be coupled using the
single 50 ° C 10 min couplpling cycle to minimize epimerization using the parameters in the table below.
Stage
Temp (
o
C)
Power (W)
Time (sec)
Delta T
1
25
0
120
2
2
50
35
480
1
Arginine
Arginine is susceptible to
γ
-lactam formation, greatly reducing the coupling efficiency. By default, Arg is coupled using a
modified double coupling cycle. Both coupling steps use the Standard Coupling microwave method.
Uronium Activation (HBTU/HATU)
Coupling cycles with uronium activation should be performed at 75°C to prevent premature quench of activated amino acid
ester. Below are exceptional cases.
Histidine
His(Trt) is susceptible to epimerization at elevated temperatures. By default, His(Trt) should be coupled using the single
50 ° C 10 min coupling cycle to minimize epimerization using the parameters in the table below. His(Boc) suppresses
epimerization at elevated temperature and can be coupled using the standard coupling microwave method.
Stage
Temp (
o
C)
Power (W)
Time (sec)
Delta T
1
25
0
120
2
2
50
50
480
1
