A PROCESS FOR PRODUCING PENTAPEPTIDES AND INTERMEDIATES FOR USE IN THE SYNTHESIS

Pentapeptides having the formula H-Asp-Ser-C-Pro-Arg-OH, where Asp, Ser, Pro and Arg may have L- or D-configuration, and C denotes Asp or Asn in L or D configuration, are synthesized by reacting in an aqueous medium Y2-Pro-OH, wherein Y2 is a protective group, with Arg-Ro, wherein Ro is OH or is as defined below for R1 below, to form Y2-Pro-Arg-Ro, which is deprotected, if necessary under conversion to Pro-Arg-R1, wherein R1 is an enzymatically cleavable alpha -carboxy substituting group selected from esters, amides, anilides, hydrazides or L-amino acid esters, and thereafter reacting Y3-C(Z3)-OH with Pro-Arg-R1 to form Y3-C(Z3)-Pro-Arg-R1, which is deprotected to C-Pro-Arg-R1, and then reacting Y4-Ser-OH with C-Pro-Arg-R1 to form Y4-Ser-C-Pro-Arg-R1, which is deprotected to Ser-C-Pro-Arg-R1, and reacting Y5-Asp(Z5)-OH with Ser-C-Pro-Arg-R1 to form Y5-Asp(Z5)-Ser-C-Pro-Arg-R1, which is deprotected to the intermediate Asp-Ser-C-Pro-Arg-R1, and finally removing the group R1 with an enzyme, preferably trypsin to form Asp-Ser-C-Pro-Arg, or removing R1 from Y5-Asp(Z5)-Ser-C-Pro-Arg-R1 before deprotection to Asp-Ser-C-Pro-Arg-OH. The groups Y2, Y3, Y4, Y5, Z3 and Z5 are protective groups which apart from Y2 are removable by catalytic hydrogenation. The employed synthesis strategy based on the combination hydrogenation/enzyme, both proceeding under mild conditions, leads to the peptides, in particular HEPP, in good yield without risk of formation of beta -aspartyl peptides and cleavage of Asp-Pro bonds.