Methods for producing N-protected-azetidine-2-carboxylic acids

Details Methods for producing N-protected-azetidine-2-carboxylic acids Methods for producing N-protected-azetidine-2-carboxylic acids

2000-06-01

2001-11-06

McKane, Joseph K. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

Reexamination Certificate

active

06313315

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an optically active N-protected-azetidine-2-carboxylic acid, which is a useful starting material for producing pharmaceuticals as described, for example, in WO98/50420 or Brain Res., 801 (1-2), p. 158, 1998.
2. Description of Related Art
Enantiomerically pure N-protected-azetidine-2-carboxylic acid such as (S)-N-benzoylazetidine-2-carboxylic acid has been produced by recrystallizing (S)-N-benzoylazetidine-2-carboxylic acid(94% e.e.) as disclosed in WO98/02568. For further derivatization to enantiomerically pure azetidine-2-carboxylic acid or a peptide, however, said compound required cumbersome alkaline hydrolysis and neutralization steps or further step of introducing a suitable protective group.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for purifying azetidine-2-carboxylic acid, which method can conveniently produce an enantiomerically pure azetidine-2-carboxylic acid with a suitable N-protective group.
The present invention provides:
a method for producing an essentially enantiomerically pure N-protected-azetidine-2-carboxylic acid of formula (1):
which method comprises:
subjecting a crude enantiomerically excess N-protected-azetidine-2-carboxylic acid comprising said enantiomer represented by formula (1) in excess to the other enantiomer thereof to crystallization in an organic solvent selected from aromatic hydrocarbon, aliphatic ether, aliphatic alcohol, aliphatic ketone, aliphatic nitrile, aliphatic amide, aliphatic sulfoxide, aliphatic ester and a mixed solvent thereof,
wherein R is:
an optionally substituted alkyl, alicyclic or alicyclicalkyl group,
an optionally substituted alkenyl group,
an optionally substituted aryl group,
an optionally substituted heteroaryl group, or
a dialkylamino group, and
absolute configuration of the asterisked asymmetric carbon atom is S or R.


REFERENCES:
patent: 5880291 (1999-03-01), Ushio et al.
patent: 0855446 (1998-07-01), None
patent: 0957089 (1999-11-01), None
patent: 0974670 (2000-01-01), None
patent: WO9702241 (1997-01-01), None
patent: WO9802568 (1998-01-01), None
patent: WO9850420 (1998-11-01), None
patent: WO0012473 (2000-03-01), None

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