Solid phase peptide synthesis of tri-peptide derivatives

1. A process for the preparation of a peptide derivative or a pharmaceutically acceptable salt thereof of formula I

wherein Tos has the meaning of p-toluenesulfonyl, comprising

a) consecutive coupling of the amino acids arginine, proline and glycine on a solid phase support in the presence of a first coupling agent/additive system, wherein the solid phase support is a 2-chlorotritylchloride-polystyrene resin and wherein further the first coupling agent/additive system is selected from the group consisting of DCC/HOBt, HBTU/HOBt, TBTU/HOBt, HATU/HOAt DEPBT/HOOBt, and PyBoP/Cl-HOBt,

b) tosylation of the N-α-amino group of the glycine moiety,

c) cleavage of the tosylated peptide or of an amino side chain protected derivative thereof from the solid phase support to form the peptide intermediate of formula II

or an amino side chain protective derivative thereof; and

d) reaction, in the presence of a second coupling agent/additive system, of the peptide intermediate of the formula

or of an amino side chain protected derivative thereof

with an aniline of the formula

R—NH 2   III

wherein R has the meaning of p-aminophenyl and wherein one amino group is protected with an amino protecting group,

wherein the second coupling agent/additive system for the reaction of the peptide intermediate of formula II with the aniline of formula III is selected from the group consisting of DCC/HOBt, HATU/HOAt, HBTU/HOBt, TBTU/HOBt, PyBOP/Cl-HOBt and DEPBT/HOOBt.

2. The process of claim 1 , wherein arginine is side chain protected with a Pbf or a Pmc protecting group.

3. The process according to claim 1 , characterized in that proline is applied in the form of Fmoc-(L)-Pro-OH.

4. The process according to claim 1 , characterized in that glycine is applied in the form of Fmoc-Gly-OH.

5. The process according to claim 3 , wherein the Fmoc protecting group is removed by treatment with piperidine.

6. The process according to claim 4 , wherein the Fmoc protecting group is removed by treatment with piperdine.

7. The process according to claim 1 , wherein the first coupling agent/additive system is HBTU/HOBt.

8. The process according to claim 1 , wherein the second coupling agent/additive system is DEPBT/HOOBt.

9. The process according to claim 1 , wherein the tosylation takes place with 4-toluenesulfonylchloride.

10. The process according to claim 1 , wherein the cleavage from the solid phase support of step c) is accomplished with trifluoroacetic acid.

11. The process according to claim 1 , wherein the reaction with the aniline of formula III in step d) is performed with Tos-Gly-Pro-Arg(Pbf)-OH as the amino side chain protected derivative of the peptide intermediate of formula II.