Process for the preparation of D-asparagine derivatives

Details Process for the preparation of D-asparagine derivatives Process for the preparation of D-asparagine derivatives

2001-04-12

2002-07-16

Lilling, Herbert J. (Department: 1651)

Chemistry: molecular biology and microbiology

Process of utilizing an enzyme or micro-organism to destroy...

Resolution of optical isomers or purification of organic...

C435S109000

Reexamination Certificate

active

06420166

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a new process for the preparation of D-asparagine derivatives of formula I
wherein R
1
is an amino protecting group and R
2
is an alkyl, a substituted alkyl or a group of formula A
R
3
(OCH
2
CH
2
)
n
—  A
wherein R
3
is hydrogen or a lower alkyl group and n is 1, 2 or 3.
Compounds of formula I are known. The compound N-benzyloxycarbonyl-D-asparaginemethylester is described in J. Liq. Chrom. (1994), 17 (13), 2759. A chemical synthesis of this compound is described in Tetrahedron (1997), 53 (6), 2075, where it is accomplished by a two-step reaction starting with already chiral (S)-asparagine. In a similar way, as described in Tetrahedron Asymmetry (1992), 3 (10), 1239, N-protected (S)-asparagine methyl ester is prepared in a two-step reaction, starting with already chiral N-protected (S)-asparagine. In J. Chem. Soc. Perkin Trans 1 (1983), 2287 the synthesis of the above-mentioned compound is described, starting also with a chiral reactant.
In EP 0 950 706 and in EP 0 896 057 the production and purification of novel D-aminoacylases from a microorganism belonging to the genus Sebekia or Amycolatopsis, respectively, is described. The enzymes are useful for the industrial production of chiral D-amino acids starting with racemic N-acetyl-D,L-amino acids. The D-aminoacylase (genus Sebekia) has an activity towards N-acetyl-D-asparagine of 1.4% as compared to N-acetyl-D-methionine (100%). The D-aminoacylase (genus Amycolatopsis) has a specific activity towards N-acetyl-D-asparagine of 19% as compared to N-acetyl-D-methionine (100%).
In Agric. Biol. Chem. (1987), 51 (3), 721 and in DE 2825245 the enzymatic preparation of D-amino acids, starting with D,L-5-substituted hydantoin, is described. The synthesis of D-asparagine is accomplished in a two-step reaction ( first: ring opening of D,L-5-substituted hydantoins to D-N-carbamyl amino acids by D-hydantoin hydrolase, followed second by the cleavage of N-carbamyl-D-amino acids to D-amino acids by N-carbamyl-D-amino acid hydrolase using Genus Pseudomonas AJ-1122) or in a one-step reaction using Genus Pseudomonas, Achromobacter, Alcaligenes, Maraxella, Paracoccus or Arthrobacter.
No technical enzymatic reaction for the preparation of asparagine ester derivatives has been described in the literature. This might be due to the ease of racemization and degradation of asparagine derivatives at the conventional pH-values (7-8.5) used for hydrolase reactions. A rapid inactivation of the enzymes was observed when higher, technical, more relevant substrate concentrations were used.
SUMMARY OF THE INVENTION
The present invention provides a process for the preparation of D-asparagine derivatives of formula I
wherein R
1
is an amino protecting group and R
2
is an alkyl, a substituted alkyl or a group of formula A
R
3
(OCH
2
CH
2
)
n
—  A
wherein R
3
is hydrogen or a lower alkyl group and n is 1, 2 or 3, comprising:
a) reacting a compound of formula II
wherein R
1
and R
2
are as defined above, with a protease in an aqueous solution at a pH of 6.0-7.5 and an organic solvent, and
b) extracting the D-asparagine derivative of formula I.
The present invention also provides a process for the preparation of N-protected L-asparagine of formula III
wherein R
1
is an amino protecting group and R
2
is an alkyl, a substituted alkyl or a group of formula A
R
3
(OCH
2
CH
2
)
n
—  A
wherein R
3
is hydrogen or a lower alkyl group and n is 1, 2 or 3, comprising:
a) reacting a compound of formula II
wherein R
1
and R
2
are as defined above, with a protease in an aqueous solution at a pH of from 6.0-7.5 and an organic solvent,
b) extracting a D-asparagine derivative of formula I; and
c) treating the aqueous layer from the extraction of step b) to obtain the N-protected L-asparagine of formula III.
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, it has now been found, that enzyme inactivation during the preparation of asparagine ester derivatives could be overcome by employing an organic solvent. (The effect of the solvent is not that of a “substrate solubilizer” since if it is added after the reaction has come to a stop, the reaction does not resume.) The compounds of formula I can be prepared in an improved way by the process of the present invention. The process of the invention provides for the preparation of D-asparagine derivatives of formula I
wherein R
1
is an amino protecting group and R
2
is an alkyl, a substituted alkyl or a group of formula A
R
3
(OCH
2
CH
2
)
n
—  A
wherein R
3
is hydrogen or a lower alkyl group and n is 1, 2 or 3, which process comprises reacting a compound of formula II
wherein R
1
and R
2
are as defined above, with a protease in an aqueous system, i.e., an aqueous solution, at a pH of 6.0-7.5 and an organic solvent, and subsequent extraction of the enantiomeric pure product of formula I.
In the structural formulae presented herein a wedged bond (
) denotes that the substituent is above the plane of the paper.
In the structural formulae presented herein a dotted bond (
) denotes that the substituent is below the plane of the paper.
The term “amino protecting group” as used herein refers to groups such as those employed in peptide chemistry as described in Green, T., Protective Groups in Organic Synthesis, Chapter 5, John Wiley and Sons, Inc. (1981), pp. 218-287, such as an allyloxy-carbonyl group (ALLOC), a lower alkoxycarbonyl group (e.g. tert.-butoxycarbonyl (t-BOC)), a substituted lower alkoxycarbonyl group (e.g. trichloroethoxycarbonyl), an optionally substituted aryloxycarbonyl group (e.g. p-nitrobenzyloxycarbonyl, benzyloxycarbonyl (Z) or phenyloxycarbonyl), an arylalkyl group (e.g. triphenylmethyl (trityl), benzhydryl or benzyl), an alkanoyl group (e.g. formyl, acetyl), an aroyl group (e.g. benzoyl), a halogen-alkanoyl group (e.g. trifluoroacetyl) or a silyl protective group (e.g. tert.-butyldimethylsilyl).
Preferred amino protecting groups are benzyloxycarbonyl, tert.-butoxycarbonyl, allyloxycarbonyl or benzoyl, especially preferred amino protecting group are benzyloxycarbonyl or benzoyl.
The term “alkyl” as used herein denotes straight or branched chain hydrocarbon residues containing 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 1-sec-butyl, isobutyl, tert.-butyl, pentyl, hexyl, heptyl, octyl, including their different isomers. Preferably, the term “alkyl” denotes an optionally substituted straight or branched chain hydrocarbon residue containing 1 to 5 carbon atoms.
Alkyl in R
2
is preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, 1-sec-butyl, isobutyl or pentyl and more preferred methyl or ethyl.
The term “lower alkyl” as used herein denotes straight or branched chain hydrocarbon residues containing 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, 1-sec-butyl, isobutyl or tert.-butyl.
The term “substituted alkyl” as used herein denotes a straight or branched chain hydrocarbon residues containing 1 to 8 carbon atoms in which one or more hydrogen atoms are substituted by one or more hydroxy groups, lower alkoxy groups, cycloalkyl groups, aryl groups or by one or more halogen atoms. Examples are 3-hydroxybutyl, 4-methoxybutyl, 3-ethoxypropyl, 3-cyclohexylpropyl, benzyl, 2-phenylethyl, 1-fluoromethyl, 2-chloroethyl, 2,2-dichloroethyl, 3-bromopropyl or 2,2,2-trifluoroethyl and the like.
Substituted alkyl in R
2
is preferably benzyl.
The term “cycloalkyl” as used herein denotes a 3-6 membered saturated carbocyclic moiety, e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl, preferably cyclohexyl.
The term “lower alkoxy” as used herein denotes a straight or branched chain lower alkyl-oxy group wherein the “lower alkyl” portion is as defined above. Examples are methoxy, ethoxy, n-propyloxy, iso-propyloxy, n-butyloxy, iso-butyloxy or tert.-butyloxy. More preferred lower alkoxy groups within the invention are methoxy or ethoxy.
The term “aryl” as used herein denotes an optionally substituted phenyl group in which one or more aryl hydrogen atoms may

Affiliated with

Also associated with

Rating

Process for the preparation of D-asparagine derivatives does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for the preparation of D-asparagine derivatives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of D-asparagine derivatives will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2816840