Patent ID: 7122628

Claim:
A process for making a peptide of the formula (I), ρGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH 2 , (I) wherein said process comprises: (a) temporarily protecting the indole-NH group on the side chain of any tryptophan residue with a side chain protecting group; (b) temporarily protecting the side chain of the histidine residue with a side chain protecting group; (c) attaching a cesium salt of Boc-Gly onto a chloromethylated polystyrene resin to yield Boc-Gly resin; (d) deblocking Boc-Gly-resin by mixing the Boc-Gly-resin with a mixture of a Boc-deblocking organic acid to yield an organic acid salt of H 2 N-Gly-resin; (e) neutralizing the organic acid salt of H 2 N-Gly-resin with a base to yield H 2 N-Gly-resin; (f) successively coupling H 2 N-Gly-resin with a Boc-α-amine protected amino acid, said protecting amino acid corresponding to ρGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH 2 in the order shown from the C-terminal to the N-terminal, wherein said coupling comprises: (i) reacting H 2 N-Gly-resin with the Boc-α-amine protected amino acid in the presence of a peptide coupling agent to yield a Boc-blocked coupled product; (ii) deblocking the Boc group from the Boc-blocked coupled product by mixing the Boc-blocked coupled product with a Boc-deblocking organic acid to yield a coupled product; (iii) reacting the coupled product with a next Boc-α-amine protected amino acid in the presence of a peptide coupling agent to yield a Boc-blocked coupled product; (iv) deblocking the Boc group from the Boc-blocked coupled product by mixing the Boc-blocked coupled product with a Boc-deblocking organic acid to yield a next coupled product; (v) repeating steps (d)(iii) and (d)(iv) until the N-terminal amino acid of the peptide of formula (I) has been coupled and the Boc group of the N-terminal amino acid has been deblocked to yield a protected completed peptide-resin; (vi) removing said side chain protecting group on the histidine residue; (g) deprotecting the protected indole-NH group on the side chains of the tryptophan residues and cleaving the completed peptide-resin to yield ρGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH 2 , wherein said deprotecting and cleaving comprises: (i) making a solution of the protected completed peptide-resin in an alcohol/inert polar aprotic solvent mixture; (ii) cooling the solution to about 0° C. to about 10° C.; (iii) bubbling ammonia gas slowly and maintaining cooling until the solution is well saturated with ammonia to yield a saturated solution; (iv) mixing the saturated solution without cooling for about 15–36 hours until <95% of free methyl ester is converted to the corresponding amide; and (h) isolating ρGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH 2 from said solution.