DE2033600C3 - L-Pyrogluta myl-L-Wstidyl- L-pro-Hnamid derivatives and processes for their preparation - Google Patents

Description

Ac-NH-CH-COOH

CH ₂
CH ₂
CO
NHR ₄

(I)

35

in which R _{4 is} hydrogen, the 4,4'-dimethoxybenzhydryl radical (Mbh) or the 2,4-dimethoxybenzyl, 2,4,6-trimethoxybenzyl or xanthyl radical and Ac is the tert-butyloxycarbonyl, the benzyloxycarfconyl, the adamantyloxycarbonyl - Or denotes the isobornyloxycarbonyl radical, according to the methods customary in peptide chemistry with the compound of the formula II

CH ₇ -CH,

NH ₂ -CH-CO-N _n

CH ₂
C—

CH
\

-N

Il
CH

N
H

CH-CH ₂

CO -NH-Mbh

(H)

or

b) the compound of the formula III, in which Ac has the abovementioned meaning,

Ac-NH-CH-CO-NH-CH-COOH

CH ₂
CH ₂
CO

NH-Mbh

CH ₂
C -

CH

N
H

-N

Il
CH

(III)

according to the methods customary in peptide chemistry with L-prolinamide or L-proline-4,4'-dimethoxybenzhydrylamide converts and the compounds of formula IV obtained

CH ₂ -CH ₂

Ac-NH-CH-CO-NH-CH-CO-N

CH,
CH,
CO
NH-R ₄

CH ₂

CH

N H

-N

CH-CH ₂
CO-NH-R ₅

(IV)

in which R _{5 has} the meaning H or Mbh, but R ₄ and R ₅ cannot be hydrogen at the same time, heated under reflux with anisole- or phenol-containing trifluoroacetic acid and optionally (if Ac = benzyloxycarbonyl radical) the compounds obtained before treatment with trifluoroacetic acid / Catalytically hydrogenated anisole.

65

Pyroglutamic acid peptides are often difficult to obtain in one form. This is especially true for that L-pyroglutamyl-L-histidyl-L-proline-amide to that after Biochem. and Biophys. Res. Commun. 37, 705 (1969) is identical to the thyrotropin releasing factor (TRF) is. The synthesis of this tripeptide amide by common methods of peptide chemistry (see HeIv. Chim. Acta 53, 63 [197O]) encounters difficulties because all intermediate products, starting from Prolinamid and pyroglutamic acid, soluble in water and therefore difficult to handle and clean.

It has now surprisingly been found that pyroglutamyl peptides from glutamine peptides when Treat with boiling trifluoroacetic acid in a lot

Λ 4

Form good yields. It blocked the above methods with the compound of formula II AmiidgrupP ^s of Glutamine and / or the proline

ainids with protecting groups such as B. the 4,4'-Di-CH, -CH ₂

methoxybenzhydryl, the 2,4-dimethoxybenzyl, /

2,4, 6-trimethoxybenzyl or xanthyl _{radical can easily be split off by tri- 5 NH 2} -CH-CO-N fluoroacetic acid, one gets I \

too poorly water-soluble and sometimes even acetic ester-soluble Intermediate products that are easy to clean. .

The invention thus relates to a method ι ο II

ζω Production of L-pyroglutamyl-L-histidyl- CH

L-proline amide, which is characterized in that \ /

one either N

a) a compound of the formula I H

CH ₂ C—

-N
CH

CH-CH ₂

CO - NH- Mbh

'5

or

b) the compound of the formula III, in which Ac has the abovementioned meaning,

Ac-NH-CH-CO-NH-CH-COOH

Ac-NH-CH-COOH CH ₂
CH ₂
CO
NHR ^

in which R is hydrogen, the 4,4'-dimethoxybenzhydryl

rest (Mbh) or the 2,4-dimethoxybenzyl, 2,4,6-tri

methoxybenzyl or xanthyl radical and Ac denotes the tert- ₃ o according to the methods customary in peptide chemistry

Butyloxycarbonyl-, the benzyloxycarbonyl-, the Ada- L-prolinamide or L-proline-4,4'-dimethoxybenzhy-

mantyloxycarbonyl- or isobornyloxycarbonyl- drylamid and the compounds obtained

rest means, according to the formula IV customary in peptide chemistry

CH ₂ CH ₂ (III) CH ₂ CO NH-Mbh CH
\ \ /
N
H -N
η Il
CH

Ac — NH- CH- CO - NH- CH- CO-

CH ₂ CH ₂

CH ₂ C -

I Il

CO CH

I \

NH- R "

-N

Il

CH CH ₂ -CH ₂

CH-CH ₂
CO-NH-R ₅

(IV)

in which R _{4 has} the meaning H or Mbh, but R ₄ and R ₅ cannot be hydrogen at the same time, heated under reflux with anisole- or phenol-containing trifluoroacetic acid and optionally (where Ac = benzyloxycarbonyl radical) the compounds obtained before treatment with trifluoroacetic acid / Catalytically hydrogenated anisole.

The L-pyroglutamyl-L-histidyl-prolinamide produced according to the invention is chromatographically pure without further purification and has high TRF activity.

The process for the production of L-pyroglutamyl-L-liistidyl-L-prolinamide is particularly advantageous since ( _{) 0} always poorly water-soluble intermediates are formed which make isolation and purification considerably easier.

The L-histidyl- (> <, L-proline-4,4'-dimethoxybenzhydrylamide of the formula II, which is obtained by catalytic hydrogenation from the cut to be cleaned ben / yloxycarbonyl-L-histidyl-

NH L-proline-4,4'-dimethoxybenzhydrylamide can be produced. This compound can be reacted with the L-glutamine derivatives of the general formula 1 to give the tripeptide derivatives of the general formula IV (R ₄ , R ₅ = Mbh or R ₄ = H, R ₅ = Mbh). The use of derivatives of the general formula i, in which R denotes the Mbh radical, is particularly favorable, since any other peptide synthesis methods, for example the anhydride or ynamine method or the synthesis with Woodward's reagent K, can also be used with these due to the protection of the amide function can without, as is often the case with amide-protected glutamine derivatives, the amide group is dehydrated to the cyano group or that (i-amino-glutarimide derivatives are formed.

N "- Benzyloxycarbonyl - N ^v - 4,4 '- dimethoxybenzhyilryl-L-glutamine is obtained, for example, according to Proc. 9th Europ. Peptide Symp., North Holland Publishing Comp., Amderstam (1968), page 89, by reacting benzyloxycarbonyl-L -glutamine with 4,4'-dimethoxybenzhydrol in glacial acetic acid under H ₂ SO ₄ -catalysis-

solved. ^{7.2 g of dicyclohexylcarbodiimide in 12 ml of chloroform are added at 0} ° C. and the mixture is stirred for a further 3 hours at room temperature. The chloroform is then distilled off regardless of the precipitate, and the residue is taken up in 60 ml of warm dimethylformamide. The dissolved dicyclohexylurea is then filtered off and the solution is poured into 400 ml of water. The gelatinous precipitate is filtered off, washed with water and ether and turned on

placed. If the benzyloxycarbonyl group is split off from this compound bydrogenolytically and the reaction product is acylated with tert-butyloxycarbonylazide, adamantyloxycarbonyl chloride or isobornyloxycarbonyl chloride, further acyl derivatives of the general formula 1 (R ₄ = Mbh) are obtained. In the reaction of compounds of general formula I (R ₄ = H) with L-histidyl-L-proline 4.4 to synthesize de ^r Verbindun- -dimethoxybenzhydrylamid - "~

of the general formula IV (R ₄ = H; R ₅ = Mbh) dried in the air. Yield: 21.3 g. if this is advantageous in the form of their activated esters, such as. B. p-nitrophenyloster. Also with Woodwards reagent K or with dicyclohexylcarbodiimide in the presence of 1-hydroxybenzotriazole (Chem. Ber. 103 [1970], page 788) or 3-hydroxy-15 4-oxo-3,4-dihydro-1,2,3-benzotriazine the substances of the general formula I (R ₄ = H) can be combined with L-histidyl-L-proline-4,4'-dimethoxybenzhydrylamide to give compounds of the general formula IV (R ₄ = H;

b) Z-Gln (Mbh) —His — OH (III)

Dissolve 20.5 g of Z — Gln (Mbh) —His — OMe in a mixture of 40 ml of methanol, 65 ml of water and 160 ml of dioxane and saponified at pH 12.7 under Add dropwise 1N NaOH and check the pH in the autotitrator. Consumption 45.2 ml of 1N NaOH. Now

R ₅ = Mbh). The solvent used is preferably 45.2 ml of 1N HCl and the mixture is concentrated in vacuo

added dimethylformamide and dimethylacetamide.

In route b) for the preparation of compounds of the general formula IV, the compounds of the general formula Hl are used. The zwitterion N "- benzyloxycarbonyl - N '- 4,4' - dimethoxybenzhydryl-L-glutaminyl-L-histidine, which is sparingly soluble in water and organic solvents, is produced by saponifying the corresponding methyl ester. Substances of general formula III are added with L-prolinamide Compounds of the general formula IV (R ₄ = Mbh; R ₅ = H), reacted with L-piolin-4,4'-dimethoxybenzhydrylamide to give compounds of the formula IV in which R ₁ and R _{2 are} Mbh Help benzotriazine 2,3-dicyclohexylcarbodiimide in the presence of 1-hydroxybenzotriazole, N-hydroxysuccinimide or 3-hydroxy-4-oxo-3,4-dihydro-l. The condensation reactions are advantageously begins at -10 to 0 ⁰ C and leads they come to an end at room temperature, again preferred solvents are dimethylformamide and dimethylacetamide.

To split off the protective groups and at the same time cyclization of the glutaminyl radical, one boils the compounds of the general formula IV for 30 to 90 minutes in trifluoroacetic acid, which contains about 10% anisole or contains phenol. It is then evaporated to dryness in vacuo and filtered to remove adhering Trifluoroacetic acid via a basic ion exchanger, such as. B. Amberlite IR-45, IRA-400 or Serdolite blue. The filtrate is concentrated in vacuo or lyophilized.

The one produced by the method according to the invention Is L-pyroglutamyl-L-histidyl-L-piolinamide pure and is used in medicine to test the function of the pituitary gland and to treat hypothyroidism.

Examples

L-Pyroglutamyl-L-histidyl-L-proline-amide (IV)
according to path b):

1. From Z-Gln (Mbh) —His — Pro — NH ₂
(IV, R ₄ = Mbh; R ₅ = H; Z = benzyloxycarbonyl)

a) Z-GIn (MbIi) -HiS -OMe

16.5 g of Z-Gln (Mbh) -OH (I, R-Mbh), 7.85 g of H-His-OMc · 2HCl, 8.8 g of I-hydroxybenzotriazole and 9.0 ml of triethylamine are dissolved in 220 ml of chloroform small volume and mixed with plenty of water. The precipitate is boiled twice with ethanol. Yield: 11.5 g. Melting point 186 to 189 C.

c) 7 Gln (Mbh) -His — Pro — NH, (IV)
To a solution of 96.5 g

Z-GIn (MWi) - His -OH

22.6 g of H-PrO-NH ₂ HCl, 40.5 g of l-hydroxy-benzotriazole, 19.2 ml of N-ethylmorpholine and, at ⁰ ° C., a cold solution of 31 g of dicyclohexylcarbodiimide in 150 ml of dimethylformamide are added to 1 liter of dimethylformamide . The mixture is left to stir at room temperature for 1 hour and overnight. The deposited precipitate is filtered off with suction the next day and the filtrate is concentrated in vacuo. The residue is dissolved in 1.5 liters of ethyl acetate to which a little water and alcohol have been added and washed with saturated sodium bicarbonate solution and water _{, dried over NaSO 4} , and the ethyl acetate solution is concentrated in vacuo. The residue is triturated with ether and filtered off with suction. Raw dent:

97.2 g. The crude crop was boiled twice with ethyl acetate for purification. Yield: 73 g.
[a] "= -23.1 (c = 1. in 90% acetic acid).

d) L-pyroglutamyl-L-hislidyl-L-proline-anvd

51.8 g of Z — GIn (MbIi) —HiS — Pro — NH ₂ are dissolved in 520 ml of 90% acetic acid and hydrogenated with Pd-Kalaly-5 for 3 hours. The catalyst is filtered off with suction and the filtrate is concentrated in vacuo. The residue is triturated several times with ether and refluxed for 90 minutes in 5 (K) ml of trifluoroacetic acid / anisole (9: 1). The trifluoroacetic acid is (, distilled off in vacuo. The residue is triturated with ether and filtered off with suction. The substance is dissolved in 120 ml of water and passed through a column of 400 ml of Amberlite IR-45. It is eluted with water. The elual is reduced to a small amount Reduced volume, warmed up with a little activated charcoal, filtered off with suction through a clarifying layer filter and lyophilized. Yield: 17.0 g (67%).

["], = -63" (c = 1st in water).

20 33-ΘΟΟ

2. From Ζ — GIn (MbIi) -HiS-Pro-NH-Mbh
(IV, R ₄ , R ₅ = Mbh)

according to path a) and b):
a) Z-Pro-NH-Mbh

_{1 ml of concentrated H 2} SO _{4 is added} to a solution of 25 g (0.1 mol) of Z— Pro — NH _{2 and} 24 g (0.1 mol) of 4,4'-dimethoxybenzhydrol in 200 ml of glacial acetic acid and left at room temperature for 2 days stand. An oil is precipitated with 800 ml of water and soon crystallizes. The precipitate is filtered off with suction, washed with water and dissolved in ethyl acetate. The ethyl acetate _{solution is washed with NaHCO 3} solution and water, dried with sodium sulfate and concentrated in vacuo. The residue is triturated with ether and filtered off with suction. Yield: 38.1 g (80%), melting point 123 to 126 ° C. Thin-layer chromatography was still able to detect a little Z — PrO — NH ₂ . For cleaning, it is precipitated from ethanol / water. Yield: 36.65 g (77%), melting point 119 122 ' ¹ C.

["], = -5, l" (c = 1, dimethylacetamide).
C ' ₂ hH.ioN ₂ 0 ₅ (474.6):

Calculated ... C 70.88. H 6.34. N 5.92:

found .... C 70.8. H 6.1, N 5.9.

b) H - Pro - NH - Mbh

By dissolving 29.2 g (61.6 mmol) of Z — Pro — NH — Mbh in 200 ml of methanol, to which some Pd (OH) ₂ BaSO ₄ catalyst has been added. hydrogen is passed in, with 1N methanolic hydrogen chloride being added dropwise with the aid of an autotitrator to maintain pH 4.5. After the hydrogenation, the mixture is filtered off with suction through a silica gel filter, the filtrate is concentrated and the residue is partitioned between 60 ml of 2N soda solution and 150 ml of ethyl acetate. The liquid ester solution is dried over sodium sulfate and concentrated. The residue crystallizes on trituration with Pctrolether. Yield: 18.8 g (90%), melting point 93 98 C.

[>,] = -30.7 (c * = 1. Dimelhylacctamide).

C ₂₁₁ H ₂₄ N ₂ O ₃ (340.4):
Calculated ... C 70.57. H 7.10, N 8.23:
uc found ... C 70.0, H 7.0. N 8.6.

about 40 g of basic Al ₂ O, (Woelm, Aküvslufe I) are chromatographed. Yield: 10.5 g (86%). Γ. "] ° = ~ 3I, 6 ° (c = 1, dimethylacetamide).

TwH ₃₇ N ₅ O ,, · IH ₂ O (629.7):

Calculated ... C 64.88, H 6.25, N 11.12; found .... C 65.0, H 6.3, N 11.2.

d) Ζ — Gln (Mbh) - His— Pro — NH-Mbh (IV, R ₄ , R ₅ = Mbh)

by way a):

α) By dissolving 6.30 g (10 mmoles) of Z — His-Pro — NH-Mbh ■ IH ₂ O (II) in 100 ml of methanol to which some Pd (OH ₂ ) / BaSO ₄ catalyst has been added, hydrogen is passed in, with 1N methanolic hydrogen chloride being added dropwise with the aid of an autotitrator to maintain pH 4.5. When the hydrogenation had ended, 12.7 ml of 1N methanolic hydrogen chloride had been taken up. The catalyst is filtered off with suction and the filtrate is concentrated. The residue is dissolved in 20 ml of dimethylformamide. To this are added 1.63 ml of N-ethylmorpholine (1.27 mmol), 2.7 g (20 mmol) of 1-hydroxybenzotriazole and 5.05 g (10 mmol) of Z — Gln (Mbh) —OH (1, R = Mbh ). The mixture is cooled to 0 ° C. and then a solution of 2.1 g of DCC in 5 ml of dimethylformamide is added, the mixture is stirred for 1 hour at 0 ° C. and 1 hour at room temperature, the precipitate formed is filtered off with suction and the filtrate is concentrated. The residue is partitioned between ethyl acetate and 2N soda solution, washed with water, dried and concentrated. The residue is triturated with ether and filtered off with suction. An amorphous substance is created. Yield x 8.25 g (87%). For purification, chromatography is carried out in tetrahydrofuran over about 25 g of basic Al ₂ O ₃ (Woelm. Active level 1). Yield: 6.35 g (67%).

"[«) "= -21.4 ^C (c = 1st dimethylacetamide).

C ₅₃ H ₅₇ N ₇ O ₁₀ · IH ₂ O (970.1):

Calculated ... C 65.60. H 6.13. N 10.12: found .... C 66.1. H 6.3. N 10.0.

c) Z — His - Pro NH Mbh (II)

75 ml of ethyl acetate are added to a solution of 13 (45 mmol) Z — His — NHNH ₂ in 110 ml of 1N HCl, which has been cooled to -5 C, and an ice-cold solution of 3.15 g of NaNO ₂ in a little water is left with stirring to drip. After 5 minutes, a saturated soda solution cooled to 0 ° C. is added until the reaction mixture has an alkaline reaction. The ethyl acetate phase is separated off in a precooled separating funnel and the aqueous phase is extracted once more with cold ethyl acetate. The combined Essigesterphasen are dried at -5 ⁰ C over sodium sulfate and g at -0 ⁰ C 6.8 (2OmMoI) H -Pro-NH-Mbh offset is allowed to stand in a refrigerator overnight and the next day falls with petroleum ether. The solvent mixture is decanted from the greasy precipitating substance. Ether is rubbed into an amorphous substance. For cleaning, the substance is dissolved in tetrahydrofuran via route b):

(i) To a solution of 3.4 g (10 mmol) of H — Pro-NH-Mbh and 2.7 g (20 mmol) of 1-hydroxybenzotriazole in 40 ml of dimethylformamide are added 6.45 g (10 mmol) of Z-Gln (Mbh) - His— OH (III; and a cold solution of 2.2 g of DDC ir dimethylformamide at 0 ° C. The mixture is stirred for 1 hour at 0 ° C. A fine gelatinous precipitate is formed which, when about 20 ml of dimethylformamide is added again at room temperature, is formed internally The insolubles are filtered off and the filtrate is concentrated in vacuo. The residue is taken up in ethyl acetate and the ethyl acetate solution extracted twice with 2N sodium carbonate solution, extracted once with saturated NaCl solution, _{dried with NaSO 4 and concentrated} is triturated with ether. 9 g of an amorphous substance are formed (94.5%). For purification, tetrahydrofuran is chromatographed over basic Al ₂ O, (Woelm active stage 1). Yield: 7 4 (78%)

[..] --- 22.0 U ^ 1. Dimethylacetamide).

709 622/11

5

c) L-pyroglutamyl-L-histidyl-L-prolinamide
2.04 g (2.1 mmol)

Z — Gln (Mbh) —His — Pro — NH Mbh

with ImI anisole for 1.5-2 hours in 10 ml Trifluoroacetic acid refluxed. It is then concentrated and the residue with ether rubbed in and sucked off. The somewhat hygroscopic substance is dissolved in water. The aqueous solution is clarified with a little activated charcoal, sent over an alkaline exchanger (e.g. Scrdolil blue) and freeze-dried. Yield: 683 mg (88%) amorphous substance.

[, <] "= -58.5 ° (t- = 1.H ₂ O). , ₅

C ₁₆ H ₂₂ N ₆ O ₄ · 1 H ₂ O (380.4):

Calculated ... C 50.5, H 6.35, N 22.1:
found .... C 50.0, H 6.0, N 21.8.

3. From Z — Gin — His — Pro-NH-Mbh

(IV ₁ R ₄ = H; R ₅ = Mbh)

by way a):
a) Z — Gin — His — Pro NH-Mbh

Hydrogen is passed through the solution of 6.30 »(10 mmol) of Z — His — Pro — NH — Mbh · IH ₂ O (II) in K) OmI methanol, to which a little Pd (OH ₂ ) BaSO ₄ catalyst has been added , the pH of 4.0 being maintained by adding 0.93 N methanolic hydrogen chloride with the aid of an autotitrator. When the hydrogenation had ended, 17 ml of 0.93 N methanolic hydrogen chloride had been taken up. The catalyst is filtered off with suction and the filtrate is concentrated. The residue is dissolved in 30 ml of dimethylformamide. To this are added 2.04 ml (15.8 mmol) of N-ethylmorpholine, 2.7 g (20 mmol) of 1-hydroxybenzotriazole and 2.8 g (10 mmol) of Z-Gin-OH (I, R = H). The mixture is cooled to 0 ° C. and a solution of 2.1 g of DDC in 5 ml of dimethylformamide is then added. allowed to stir for 1 hour at 0 ^° C. and 1 hour at room temperature, the precipitate formed is filtered off with suction and the filtrate is concentrated. The residue is partitioned between ethyl acetate, to which a little dimethylformamide is added, and 2N soda solution. The ethyl acetate phase is then shaken out with NaCl solution, dried with sodium sulfate and concentrated. The residue is triturated with ether and reprecipitated from tetrahydrofuran / ether. There are 4.15 g (56%) yield. _so

[«] = -33.5 ° (c = 1. Dimethylacetamidi.

C ₁₉ H ₄₅ N ₇ O ₈ ■ 0.5H ₂ O (748.8):
Calculated ... C 62.52, H 6.19, N 13.1;
found .... C 62.6, H 6.2, N 12.9.

v>

40 li) l.-l'yroglulamyl-L-histidyl-l.-prolinamide

I g (1.34 HiMoI) Z Gin- His Pro NH M hl willow refluxed with 0.5 ml of anisole for 1.5 2 hours in 5 M trilluoroacetic acid. Subsequently is processed as usual. Yield: 366 mi (72%). Thin-layer chromatography with L-pyroglulamyl-L-histidyl-L-prolinamide identical.

4. From Boc-Gin-His Pro -NH-MbIi
(Boc = tert-butyloxycarbonyl)

by way a):
a) Boc-Gin-His-Pro -NH Mbh

Hydrogen is passed through a solution of 5.75 g (9.13 mmol of Z-His — Pro — NH-Mbh. IH ₁ O 111) in 100 m of methanol, to which a little Pd (OH ₂ ) "/ BaSO ₄ catalyst is added, whereby by adding 0.93 N methanolic hydrogen chloride dropwise using an autotitrator to maintain pH 4. After the hydrogenation, 15.5 m (14.4 mmol) 0.93 N methanolic hydrogen chloride had been taken up. The catalyst is filtered off with suction and the filtrate The residue is dissolved in 20 ml of dimethylformamide, 1.85 ml (14.4 mmol) of N-ethylmorpholine and 3.5 μl of Boc-Gin-ONp are added and the mixture is left to stand for 3 days at room temperature distilled off and the residue partitioned between ethyl acetate and 2N sodium carbonate solution. The ethyl acetate phase is extracted once more with 2N sodium carbonate solution and twice with water, dried with sodium sulfate and concentrated. The residue is triturated with ether. Yield: 5.55 g (86%) %). Zui cleaning can be done in tetrahydrofuran via basic Al ₂ O ₃ chromatographies.

I «]. · = -36.9 '(c = 1, dimethylacetamide).

b) L-pyroglutamy 1-L-histidy 1-L-prolinamide
563.6 mg (0.799 mmol)

Boc - Gin - His - Pro - NH Mbh

are mixed with 0.5 ml of anisole for 1 hour in 5 ml of trifluoric acid refluxed. Then we worked up like ubhch. Yield: 225 mg (74%) Thin-layer chromatography with L-pyroglutamyl L-histidyl-L-prolinamide identical.

Claims (6)

Patent claims:
1. Tripeptide derivatives of the general formula R-Gin-His-Pro-NH-R ₃ wherein RZ or Boc and, when R is Z, R ₂ and R _{3 are} hydrogen or the 4,4'-dimethoxybenzhydryl radical (Mbh), but not simultaneously hydrogen, and, if R is Boc, R _{2 is} hydrogen and R ₃ Mbh means 2. Z-Gln (Mbh) -His-Pro-NH-Mbh. 3. Z-G! N (Mbh) -His-Pro-NH ₂ . 4. Z-Gin-His-Pro-NH-Mbh. 5. Boc-Gin-His-Pro-NH-Mbh. 6. Process for the production of L-pyroglut- • myl-L-histidyl-L-proline amide, characterized in that one either a) a compound of formula I.