TBTU

TBTU This reagent has similar properties as HBTU. It is an excellent coupling reagent and liberates non-toxic tetramethylurea upon reaction. Couplings using TBTU proceed smoothly with little racemization and can be enhanced by adding 1- hydroxybenzotriazole (HOBt). Coupling with TBTU

1. Dissolve 2.0 equivalents (based on resin substitution) of the protected amino acid in N,N-dimethylformamide (DMF) (5 mL/g of resin).

2. Add 2.0 equivalents (based on resin substitution) of 1.0 M TBTU solution and 4.0 equivalents (based on resin substitution) of diisoproplyethylamine (DIPEA). 2.0 equivalents (based on resin substitution) of 0.5 M HOBt solution in DMF can be added to suppress racemization.

3. Remove the N-protecting group using standard deprotection protocols.

4. Add the preactivated amino acid solution. Mix for 10-60 minutes until the Kaiser test is negative.

5. Filter the resin and wash it with DMF.