NOVEL AZETIDINE DERIVATIVE AND PROCESS FOR PREPARATION THEREOF

Abstract: Novel optically active or racemic azethidine carboxylic acid derivatives (azethidine-2-carboxylic acid N-carboxyamino acid anhydrides) which are useful as drug intermediates and an industrially advantageous process for producing the same are provided. Namely, a process for obtaining azethidine-2-carboxylic acid N-carboxyamino acid anhydrides starting with azethidine-2-carboxylic acids is provided. Via the azethidine-2-carboxylic acid N-carboxyamino acid anhydrides according to the invention, azethidine derivatives having peptide bond, which are useful as drugs, can be obtained by an industrial and economic process without resorting deblocking reaction.

Description: Technical Field: This invention relates to novel azetidine derivatives and a process for producing these compounds from azetidine-2-carboxylic acids. More particularly, it relates to azetidine-N,2-dicarboxylic acid anhydrides represented by the following formula (1): and a process for producing these compounds from azetidine-2-carboxylic acids represented by the following formula (4): The azetidine-N,2-dicarboxylic acid anhydrides represented by the formula (1) are useful compounds as intermediates of drugs and the like. Background Art: The azetidine-N,2-dicarboxylic acid anhydrides represented by formula (1) are novel compounds and no prior art has been reported hitherto concerning any processes for producing these compounds. Azetidine derivatives having a peptide bond, which have a thrombin inhibitory activity, are highly useful as drug intermediates (USP 5, 714,485 and WO98/50420). These drug intermediates can be produced starting with (S)-azetidine-2-carboxylic acid which can be prepared by a publicly known method. However, condensation of an azetidine-2-carboxylic acid with an amine can be hardly performed in a single step in general. Namely, it is needed that the amine moiety of the azetidine-2-carboxylic acid is protected with a carbamate protective group, etc. followed by the condensation with the use of a condensing agent such as 1,3-dicyclohexylcarbodiimide (DCCD) and deblocking of the N-protective group. Therefore, it has been required to develop a more convenient production process. Mathre et al., J. Org. Chem., 1991, 56, 751-762, describe a method of enantioselective synthesis of α,α-diaryl-2-pyrrolidonemethanols from proline. In the first step of this synthesis, proline is reacted with phosgene in tetrahydrofuran, followed by addition of triethylamine, which induces cyclization of the intermediate N-(chlorocarbonyl)-proline, to give a proline-N-carboxanydride (Pro-NCA). Subsequently, the reaction of the Pro-NCA species with a Grignard reagent allows the desired α,α-diaryl-2-pyrrolidonemethanols to be obtained. WO-99/03467 describes the use of pyrrolidine derivatives (in particular,α,α-diaryl-2-pyrrolidinemethanol compounds) in the treatment of compulsive disorders. In this document, the synthesis of the compounds used is preferably carried out by the route of Mathre et al. or by an analogous route involving formation of a cyclic anhydride intermediate from proline and phosgene. Shalati et al., J. Polymer Sci., 1984, 22, 107-120, describe the attempted polymerization of pipecolic acid N-carboxyanhydrides (NCAs). Cyclic dipeptides are obtained by dimerization. The pipecolic acid NCAs are obtained from the corresponding N-carbobenzoxy-protected pipecolic acids by reaction with phosphorus pentachloride. Disclosure of the Invention: This invention provides intermediate compounds useful in producing drugs, in particular, azetidine derivatives having a peptide bond and a process for producing the same. Under the above-described conditions, the inventors have conducted intensive studies. As a result, they have found out that azetidine derivatives having a peptide bond can be efficiently produced via azetidine-N,2-dicarboxylic acid anhydrides, which are novel compounds, without resort to the deblocking procedure. The invention has been completed based on this finding. Accordingly, the invention provides optically active azetidine-N,2-dicarboxylic acid anhydrides and racemate thereof, which are useful in producing azetidine derivatives having a peptide bond, and a process whereby these compounds can be efficiently and economically produced on an industrial scale. Best Mode for Carrying Out the Invention: The optically active azetidine-N,2-dicarboxylic acid anhydrides and racemate thereof provided by the invention are compounds represented by the following formula (1): The term "optically active compound" as used herein means one of the (S)- and (R)-enantiomers alone of an azetidine-N,2-dicarboxylic acid anhydride or a mixture of these enantiomers containing one of them at a higher mixing ratio. On the other hand, the term "racemate" as used herein means a mixture containing the (S) - and (R) -enantiomers in the same amounts. Next, the process for producing an azetidine-N,2-dicarboxylic acid anhydride will be described. An azetidine-2-carboxylic acid to be used as the starting material in the invention can be produced by, for example, the process described in WO98/47867. An azetidine-N,2-dicarboxylic acid anhydride can be easily produced by reacting an azetidine-2-carboxylic acid with phosgene, di-phosgene and/or tri-phosgene. Phosgene is used in an amount of generally from 0.1 to 10 mole equivalents, preferably from 1 to 5 mole equivalents, as much as the azetidine-2-carboxylic acid. Di-phosgene is used in an amount of generally from 0.1 to 10 mole equivalents, preferably from 0.5 to 5 mole equivalents, as much as the azetidine-2-carboxylic acid. Tri-phosgene is used in an amount of generally from 0.1 to 10 mole equivalents, preferably from 0.3 to 5 mole equivalents, as much as the azetidine-2-carboxylic acid. Although the reaction may be carried out without using any solvents, it is usually performed in an organic solvent. Examples of the solvent, in case of using, involve ether solvents such as diethyl ether, diisopropyl ether, tetrahydrofuran, 1,4-dioxane and tertiary-butyl ethyl ether; ester solvents such as ethyl acetate, methyl acetate, propyl acetate and methyl propionate; hydrocarbon solvents such as pentane, hexane, heptane, cyclohexane, petroleum ether, toluene, benzene and xylene; nitrile solvents such as acetonitrile and propionitrile; ketone solvents such as acetone and ethyl methyl ketone; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxide solvents such as dimethyl sulfoxide; and halogenated hydrocarbon solvents such as methylene chloride, chloroform and carbon tetrachloride. Among all, ether solvents are preferable and tetrahydrofuran is most desirable. Either one of these solvents or a mixture of two or more thereof may be used. The solvent is usually employed in an amount of from 1 to 50% by weight, preferably from 5 to 30% by weight, based on the azetidine-2-carboxylic acid, though the invention is not restricted thereto. The reaction temperature varies depending on the reactants and reaction solvent employed. Usually it ranges from -50 to 100°C, preferably from -10 to 80°C and still preferably from 30 to 60°C. The reaction time may be arbitrarily selected within a scope of usually from 0.5 to 10 hours, preferably from 2 to 7 hours and still preferably from 3 to 5 hours. The compound (1) thus produced and its enantiomers can be collected as a compound having an arbitrarily high purity by optionally subjecting to publicly known separation and purification procedures such as concentration, extraction, chromatography and recrystallization. The azetidine-N,2-dicarboxylic acid anhydrides produced by the process according to the invention can be easily introduced into azetidine derivatives (azetidine-2-carboxylic acid amides) having a peptide bond by reacting with an amine. For example, (S)-azetidine-2-carboxylic acid (4-aminocyclohexyl) methanamide can be obtained by adding a THF solution containing (S)-azetidine-N,2-dicarboxylic acid anhydride to a liquid mixture of a 1 M sodium hydroxide solution containing (4-aminocyclohexyl)methanamine and tetrahydrofuran (THF) under ice-cooling followed by stirring. Example: To further illustrate the invention in greater detail, the following example will be given. However, it is to be understood that the invention is not construed as being restricted thereto. Example Synthesis of azetidine-N,2-dicarboxylic acid anhydride At room temperature, (S)-azetidine-2-carboxylic acid (1.0 g, 99.9%ee or higher) was suspended in 25 ml of tetrahydrofuran. Then tri-phosgene (1.0 g) was added thereto. The suspension was heated to 50°C and stirred for 4 hours. After allowing to cool, the solvent was distilled off under reduced pressure to give a pale yellow oil (1.5 g). 1 HNMR(CDCl3) δ 4.52 (dd, 1H), 3.76-3.62 (m, 2H), 2.44-2.36 (m, 1H), 2.23-2.14 (m, 1H), CNMR (CDC13) δ 169.10, 152.27, 55.44, 40.37, 34.22. To confirm the optical purity, the azetidine-N,2-dicarboxylic acid anhydride thus formed was hydrolyzed into azetidine-2-carboxylic acid and then analyzed by HPLC. The (S)-azetidine-2-carboxylic acid thus obtained showed an optical purity of 99.9%ee or higher. Conditions for HPLC: column Sumichiral: OA-6000 (Sumitomo Chemical Analysis Service) mobile phase: 2 mM aqueous solution of copper sulfate flow rate: 0.5 ml/min detection wavelength: 254 nm temperature: 30°C. Industrial Applicability: The invention provides novel azetidine-N,2-dicarboxylic acid anhydrides which are useful as drug intermediates and a process by which these compounds can be industrially advantageously produced.

Claims: An optically active or racemic azetidine-N,2-dicarboxylic acid anhydride represented by the following formula (1): wherein * represents an asymmetric carbon. (S)-Azetidine-N,2-dicarboxylic acid anhydride represented by the following formula (2): (R)-Azetidine-N,2-dicarboxylic acid anhydride represented by the following formula (3): A process for producing an azetidine-N,2-dicarboxylic acid anhydride represented by the following formula (1): wherein * represents an asymmetric carbon; from an azetidine-2-carboxylic acid represented by the following formula (4): wherein * represents an asymmetric carbon. The production process as claimed in claim 4 for producing (S)-azetidine-N,2-dicarboxylic acid anhydride from (S)-azetidine-2-carboxylic acid. The production process as claimed in claim 4 for producing (R)-azetidine-N,2-dicarboxylic acid anhydride from (R)-azetidine-2-carboxylic acid. A production process as claimed in any of claims 4 to 6 characterized in that cyclization is carried out by treating with phosgene, di-phosgene and/or tri-phosgene.

Inventors: MATSUO KAZUHIKO, TSUKUYA KENTARO, MATSUO, KAZUHIKO, TSUKUYA, KENTARO
Applicants: KANEKA CORP, KANEKA CORPORATION
Application year: 2001
Main classification: C07D498
IPC codes: C07D498