Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-10-09
2004-01-27
Chang, Ceila (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C548S317100, C548S320500, C548S321100, C548S499000
Reexamination Certificate
active
06683190
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel process for preparing chiral amino acids from racemic hydantoins and to the use of the said chiral amino acids as synthesis intermediates of chiral organic compounds.
PRIOR ART
Numerous processes for preparing chiral amino acids exist in the literature, based principally on processes of resolving racemic mixtures by liquid chromatography, resolution by means of alkaloids or by an enzymatic process, as for example in the as yet unpublished French patent application No. 98 06339.
These various processes of resolution present the disadvantages of being processes which are difficult to implement industrially and are of relatively high cost. In effect, the methods used are expensive.
The industrial processes—by industrial processes are meant any preparation processes other than laboratory preparations—for preparing chiral amino acids therefore necessitate enantioselective syntheses, i.e. syntheses which lead only to the single desired enantiomer and do so with a high enantiomeric purity.
Processes for preparing amino acids from hydantoins are known, for example, from the patents JP 60224661 and JP 62103049. However, these processes lead to racemic amino acids.
In contrast, the patent EP-A-739978 presents a process for preparing optically pure amino acids from racemic hydantoins.
This type of process has the drawback of employing an enzymatic reaction and of comprising a plurality of steps. This has a direct consequence on the complexity of the industrial process, on the yields of product obtained and on the production costs.
It is an object of the present invention to provide a process for preparing chiral amino acids from racemic hydantoins which does not entail the abovementioned drawbacks.
It is an object of the present invention to provide a process for preparing substantially enantiomerically pure amino acids from racemic hydantoins.
It is another object of the present invention to provide a process for preparing substantially enantiomerically pure amino acids from racemic hvdantoins which comprises only a single step (one-pot reaction), without isolation of the chiral hydantoin intermediate.
It is another object of the present invention to provide a process for preparing substantially enantlomerically pure amino acids from racemic hydantoins with a high yield.
It is an additional object of the present invention to provide a process for preparing substantially enantiomerically pure amino acids from racemic hydantoins which is easy to implement industrially and is of low cost.
It has now been found that all of these aims may be achieved in whole or in part by virtue of the process of the invention, whose description is presented below.
BRIEF DESCRIPTION OF THE INVENTION
The present invention consists in a novel process for preparing chiral amino acids of formula (I):
characterized in that a racemic hydantoin of formula (II):
is contacted with an enantiomeric resolving agent, where, in the compounds of formulae (I) and (II):
R
1
and R
2
are different and are selected from:
an alkyl or haloalkyl radical containing from 1 to 6 carbon atoms in a linear or branched chain;
an alkoxyalkyl, alkylthioalkyl, alkylsulphonylalkyl, monoalkylaminoalkyl, alkenyl or alkynyl radical containing from 2 to 6 carbon atoms in a linear or branched chain;
a dialkylaminoalkyl or cycloalkyl radical containing from 3 to 7 carbon atoms in a linear or branched chain;
an aryl radical, i.e. phenyl, naphthyl, thienyl, furyl, pyridyl, benzothienyl, benzofuryl, qulnolinyl, isoquinolinyl or methylenedioxyphenyl radical, optionally substituted by from 1 to 3 groups selected from R
6
; and
an arylalkyl, aryloxyalkyl, arylthioalkyl or aryisulphonylalkyl radical, the terms aryl and alkyl having the definitions given above;
or else
R
2
and R
2
, together with the carbon atom to which they are attached on the ring, may form a carbocycle or a heterocycle containing from 5 to 7 atoms, it being possible for these rings to be fused with a phenyl optionally substituted by from 1 to 3 groups selected from R
6
;
R
6
represents a radical selected from:
a halogen atom;
an alkyl, haloalkyl, alkoxy, haloalkoxy, alkylthio, haloalkylthio or alkylsulphonyl radical containing from 1 to 6 carbon atoms;
a cycloalkyl, halocycloalkyl, alkenyloxy, alkynyloxy, alkenylthio, alkynylthio radical containing from 3 to 6 carbon atoms;
the nitro or cyano group;
an amino radical optionally mono- or disubstituted by an alkyl or acyl radical containing from 1 to 6 carbon atoms or alkoxycarbonyl radical containing from 2 to 6 carbon atoms; and
a phenyl, phenoxy or pyridyloxy radical, these radicals being optionally substituted by from 1 to 3 identical or different groups selected from R
7
; and
R
7
represents a radical selected from:
a halogen atom selected from fluorine, chlorine, bromine and iodine;
a linear or branched alkyl radical containing from 1 to 6 carbon atoms;
a linear or branched alkoxy or alkylthio radical containing from 1 to 6 carbon atoms;
a linear or branched haloalkoxy or haloalkylthio adical containing from 1 to 6 carbon atoms;
a nitrile radical; and
a nitro radical.
The chiral amino acids thus obtained may serve as synthesis intermediates in the preparation of chiral active substances which are useful particularly in therapy or in agriculture. By way of example, these chiral amino acids may be used as intermediates in the preparation of certain fungicidal 2-imidazolin-5-ones and 2-imidazoline-5-thiones described in the patent EP-A-0 629 616.
DETAILED DESCRIPTION OF THE INVENTION
The present invention concerns a novel process for preparing chiral amino acids of formula (I):
in which:
R
1
and R
2
are different and are selected from:
an alkyl or haloalkyl radical containing from 1 to 6 carbon atoms in a linear or branched chain;
an alkoxyalkyl, alkylthioalkyl, alkylsulphonylalkyl, monoalkylaminoalkyl, alkenyl or alkynyl radical containing from 2 to 6 carbon atoms in a linear or branched chain;
a dialkylaminoalkyl or cycloalkvl radical containing from 3 to 7 carbon atoms in a linear or branched chain;
an aryl radical, i.e. phenyl, naphthyl, thienyl, furyl, pyridyl, benzothienyl, benzofuryl, cuinolinyl, isoquinolinyl or methylenedioxyphenyl radical, optionally substituted by from 1 to 3 groups selected from R
6
; and
an arylalkyl, aryloxyalkyl, arylthioalkyl or arylsulphonylalkyl radical, the terms aryl and alkyl having the definitions given above;
or else
R
1
and R
2
, together with the carbon atom to which they are attached on the ring, may form a carbocycle or a heterocycle containing from 5 to 7 atoms, it being possible for these rings to be fused with a phenyl optionally substituted by from 1 to 3 groups selected from R
6
;
R
6
represents a radical selected from:
a halogen atom;
an alkyl, haloalkyl, alkoxy, haloalkoxy, alkylthio, haloalkylthio or alkylsulphonyl radical containing from 1 to 6 carbon atoms;
cycloalkyl, halocycloalkyl, alkenyloxy, alkynyloxy, alkenylthio, alkynylthio radical containing from 3 to 6 carbon atoms;
the nitro or cyano group;
an amino radical optionally mono- or disubstituted by an alkyl or acyl radical containing from 1 to 6 carbon atoms or alkoxycarbonyl radical containing from 2 to 6 carbon atoms; and
a phenyl, phenoxy or pyridyloxy radical, these radicals being optionally substituted by from 1 to 3 identical or different groups selected from R
7
; and
R
7
represents a radical selected from:
a halogen atom selected from fluorine, chlorine, bromine and iodine;
a linear or branched alkyl radical containing from 1 to 6 carbon atoms;
a linear or branched alkoxy or alkylthio radical containing from 1 to 6 carbon atoms;
a linear or branched haloalkoxy or haloalkyithio radical containing from 1 to 6 carbon atoms;
a nitrile radical; and
a nitro radical.
In one preferred embodiment of the invention, the chiral amino acids of formula (I) are such that:
R
1
represents an aryl radical optionally substituted by from 1 to 3 groups R
6
as defined before, and
R
2
represents an alkyl or haloalkyl radical containing from 1 to 6 carbon atom
Bayer Cropscience S.A.
Chang Ceila
Ostrolenk Faber Gerb & Soffen, LLP
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