Harness for working animal
Reexamination Certificate
2000-08-08
2001-11-20
Owens, Amelia (Department: 1625)
Harness for working animal
Reexamination Certificate
active
06319187
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention provides a novel catalyst and method for the formation of amide bonds. The catalysts are derivatives of hydroxybenzotriazole (HOBT) and carry a positive charge at pH 5-7. These reagents are useful for forming compounds containing an amide bond with high purity and yield.
A wealth of procedures are available for forming amide bonds. Nonetheless, there is still room for improvement. For example, procedures have been developed which use reagents such as carbodiimides as amide coupling agents. These carbodiimides include dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). Unfortunately, these particular reagents can require a large excess of acid, can be problematic for difficult couplings with unreactive carboxylic acids and/or amines and can be difficult to purify from the reaction mixture.
Catalysts such as 1-hydroxybenzotriazole (HOBT) and derivatives thereof have also been used.
Unfortunately, HOBT and its derivatives can be difficult to remove from the reaction media.
SUMMARY OF THE INVENTION
Briefly stated, the invention is a catalyst, the use of the catalyst and a method of using the catalyst in the formation of a compound with an amide bond. The catalyst is an HOBT derivative having the following formula (1):
where R
1
is a group bearing a positive charge at pH 5-7; where Y is a bond or a substituted or unsubstituted alkylene chain containing 1-10 carbon atoms and 0-2 heteroatoms selected from the group consisting of N, S and O; and where X is a linker group selected from —CO— or —SO
2
—.
In accordance with the method aspect of the invention, an amine, a carboxylic acid, an amide coupling agent and a catalyst of formula (1) are reacted for a time sufficient to produce an amide bond between the amine and the carboxylic acid. Thereafter, the compound containing the amide bond is isolated.
In accordance with a preferred method, the reaction is carried out in solution. Also, the amide coupling agent is a carbodiimide, which carbodiimide bears a positive charge at pH 5-7. The catalyst is most preferably PP-HOBT (see formula (2) below). Finally, the compound containing the amide bond preferably does not bear a positive charge at pH 5-7 and is isolated by passing the entire reaction mixture through a cation exchange resin which traps unwanted materials and allows the desired amide product to be isolated from the eluent with excellent purity.
This preferred method, wherein the amide coupling agent and catalyst both carry a positive charge at pH 5-7, provides the advantage that the compound containing the amide bond can be readily isolated from the reaction mixture when the mixture is passed through a cation exchange resin.
As used herein and the appended claims, the term “catalyst” is intended to have a relatively broad meaning referring to a compound that facilitates the reaction between one or more other compounds, the catalyst remaining in or returning to its original state.
As used herein and the appended claims, “alkyl” means an unbranched or branched aliphatic or cyclic group containing 1-20, preferably 1-10, carbon atoms.
As used herein and the appended claims, “alkylene” means an unbranched or branched carbon chain containing 1-20, preferably 1-10, carbon atoms. Branched carbon chains include both linear and cyclic structures.
As used herein and the appended claims, “aryl” means a mono- or polycyclic carbocyclic aromatic ring containing 6 to 10 carbon atoms, such as phenyl (Ph) or naphthyl. When more than 1 ring is present, the rings can be fused or unfused.
As used herein and the appended claims, “heteroaryl” is a mono-, bi- or tricyclic, N-, O- or S-heteroaryl, such as benzofuran, benzothiophene, furan, imidazole, indole, isothiazole, oxazole, piperazine, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole, quinoline, thiazole, and thiophene.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The catalysts of the present invention have the general formula (1):
where R
1
is a group bearing a positive charge at pH 5-7;
Y is a bond or a substituted or unsubstituted alkylene chain containing 1-10 carbon atoms, and, optionally 1 or more heteroatoms such as N, S or O; and
X is a linker group selected from —CO— or —SO
2
—.
The function of R
1
is to allow the catalyst of the present invention to be removed by a cation exchange resin; thereby allowing the formed compound containing the amide bond to be purified via ion exchange chromatography. R
1
can be any group bearing a positive charge at pH 5-7. R
1
is preferably a substituted or unsubstituted, aliphatic or cyclic, dialkylamine (such that R
1
is a tertiary amine in formula (1)). Preferably, R
1
is a cyclic dialkylamine such as piperidine. Most preferably, Y is a bond and R
1
is 4-piperidino-piperidine
Y is preferably a substituted or unsubstituted alkylene chain containing 1-10 carbon atoms.
The substituents for R
1
and Y can be selected for optimization of the solubility characteristics of the catalyst in various solvents. For example, as the number of carbon atoms in the Y substituent increases, the solubility of the catalyst in nonpolar solvents is expected to improve. Alternatively, groups such as ethers and the like can be added to the R
1
or Y to enhance solubility in polar solvents.
Suitable substituents for R
1
and Y include groups which are relatively unreactive with carboxylate groups and amine groups. Examples include C
1-6
alkyl, C
1-6
alkoxy, and halogen. Amines and carboxylates are not typically suitable substituents as this would cause the catalyst to react with the starting materials, resulting in undesired side products.
Presently, —SO
2
— is preferred as the linker group X.
The most preferred embodiment of the present invention is a catalyst of the formula (2):
This particular catalyst has acceptable solubility in DMF and can be readily removed from the reaction mixture by passing the mixture through a cation exchange resin.
Preparation of the Catalyst
This most preferred catalyst, which includes a sulphonamide linker group X, may be synthesized in accordance with the following:
The chemistry depicted in this scheme is derived from Pop et al. (J. Org. Chem. 1997, 62:2594, the disclosure of which is incorporated herein by reference), who described the preparation of a resin bound HOBT.
When X is a carbonyl group, the catalysts may be prepared from 6-acyl chloride-HOBT as shown below:
Method of Amide Bond Formation
The invention also provides a method of forming a compound containing an amide bond. The steps comprise reacting an amine, a carboxylic acid, a coupling agent and a compound of the general formula (1) described above. The general reaction is represented by the following:
The reaction is carried out under conditions and for a time sufficient to produce an amide bond between the amine and the carboxylic acid.
Suitable amines (R
1
) include any compounds containing a free primary or secondary amine, including, for example, substituted or unsubstituted alkylamines, dialkylamines, arylamines and heteroarylamines. As is commonly done, HCl salts or other salts of the amines can also be used as the starting materials.
Use of the catalyst of the invention provides an advantage when the amine used in the amide formation reaction is provided in the form of an HCl salt. Typically, when using an HCI salt of an amine, a separate base is added to the reaction mixture to liberate the amine. However, the present catalyst, particularly with the tertiary amine in the R
1
group, can fill this role and eliminate the necessity to add a separate base to the reaction mixture.
Suitable carboxylic acids (R
2
—CO
2
H) include any compounds containing a free carboxylate, including, for example, substituted or unsubstituted alkylcarboxylates, arylcarboxylates or heteroarylcarboxylates.
The above amines and carboxylates can be substituted 1 or more times (preferably 1 to 3 times) with a halogen, hydroxyl, amine, alkylamine, dialkylamine, alkyl, alkoxy, alkenyl, alkylcarboxylate
Eli Lilly and Company
Joyner Charles T.
Owens Amelia
LandOfFree
Catalyst and method for amide formation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Catalyst and method for amide formation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Catalyst and method for amide formation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2591641