Chemistry: natural resins or derivatives; peptides or proteins; – Peptides of 3 to 100 amino acid residues – 4 to 5 amino acid residues in defined sequence
Patent
1996-11-04
1999-01-26
Tsang, Cecilia J.
Chemistry: natural resins or derivatives; peptides or proteins;
Peptides of 3 to 100 amino acid residues
4 to 5 amino acid residues in defined sequence
530333, 530338, 530343, C07K 700
Patent
active
058640126
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a novel active peptide and to its preparation and suitable starting materials therefor.
The PCT Application WO 93/23424 describes peptide-based active substances which have interesting antineoplastic activities. A particularly good effect is shown by the pentapeptide of Example 234 in the said application, which has the following formula: ##STR1##
Me.sub.2 Val is N,N-dimethyl-L-valine, MeVal is N-methyl-L-valine and Bzl is benzyl.
The peptide can, according to the said PCT application, be prepared by a solid-phase method starting from proline. This gives a poor yield of impure active substance. Elaborate chromatographic purification is necessary. The solid-phase method is, moreover, suitable only for preparing small amounts of substance. It has not to date proven possible to prepare the substance of Example 234 of WO 93/23424 in crystalline form. The active substance is in the form of a resin. This makes it difficult to remove residual solvent completely. Costly purification steps (spray drying, freeze drying) are necessary. Pharmaceutical processing of the substance is impeded. Larger amounts of substance are necessary for testing and launching it. A process which can be implemented industrially is needed to prepare the active substance in crystalline form if possible.
We have now found a process which affords the active substance without racemization in high purity so that the substance can be converted without difficulty into a crystalline salt, the hydrochloride.
The invention relates to a process for preparing Me.sub.2 Val--Val--MeVal--Pro--Pro--NHBzl.multidot.HCl, which comprises in a compound of the formula II
where
R.sup.1 is C.sub.1-5 -alkyl and
Z is a benzyloxycarbonyl protective group which may be substituted on the phenyl ring,
A a) eliminating the protective group Z on the N terminus, and in the resulting compound
B a) removing the alkoxy group --OR.sup.1 on the C terminus and
and converting the resulting compound into its hydrochloride.
Process A takes place in accordance with the following reaction cheme: ##STR2##
The meanings of the substituents in the above scheme as elsewhere in the description are as follows:
R.sup.1 : C.sub.1-5 -alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, pentyl and preferably methyl and ethyl,
R.sup.2 : tert-butyl, 2-ethylhexyl, C.sub.1-4 -alkoxy such as methoxy, ethoxy, isobutoxy,
Z: benzyloxycarbonyl, which is unsubstituted or substituted on the phenyl ring by halogen, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, C.sub.1-4 -acyloxy or nitro and in particular by 2-Cl, 3-Cl, 4-Cl, 4-Br, 4-CH.sub.3 O--, 4-CH.sub.3 COO--, 2-NO.sub.2 and 4- NO.sub.2
M.sup..sym. ; K.sup..sym., Na.sup..sym., Li.sup..sym. or an ammonium ion such as .sup..sym. NH(C.sub.2 H.sub.5).sub.3
Bzl:benzyl
Me: methyl.
The tetrapeptide ester II is dissolved in a suitable solvent, eg. an alcohol such as methanol, ethanol, isopropanol, butanol, an ether such as THF, dioxane, MTBE, an ester such as ethyl acetate, or glacial acetic acid. After addition of a suitable catalyst, eg. Pd/C or Pt/C, hydrogen is passed in at from 0.degree. to 50.degree. C., preferably from 10.degree. to 30.degree. C. Introduction of hydrogen can take place under atmospheric pressure or up to 10 bar. The reaction rate can be increased by allowing a certain amount of gas to escape. After hydrogen uptake is complete, 2-5 equivalents of formaldehyde are added in the form of an aqueous solution, of the gas or of paraformaldehyde. Subsequently hydrogen is passed in further under the conditions described above. The catalyst is then filtered off. IV can be purified by crystallization as hydrochloride from a suitable solvent or mixture of solvents, isopropanol/methyl tert-butyl ether having proven suitable. Traces of the Z-tetra-peptide ester II in IV can be removed by extraction methods.
The ester IV is hydrolyzed in a suitable solvent, eg. an alcohol such as methanol, ethanol, isopropanol, an ether such as MTBE, THF, dioxane, a hydrocarbon such as toluene, xylene, or a chlorinated hyd
REFERENCES:
Pettit et al., J. Am. Chem. Soc., 113(17), 6692-3. (abstract), 1991.
Pettit et al., Tetrahedron, 50(42), 12097-12108, 1994.
Gross et al., "The Peptides: Analysis, Synthesis, Biology", vol. 4, 1981, preface p. xi.
Ullmann's Enc. of Ind. Chem., vol. A19, p. 168, (1991).
Amberg Wilhelm
Bernard Harald
Buschmann Ernst
de Potzolli Bernd
Haupt Andreas
BASF - Aktiengesellschaft
Delacroix-Muirheid C.
Tsang Cecilia J.
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