# US 6,294,692 B1 · Process for producing N-formylleucine of high purity

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- Number: US 6,294,692 B1
- Document ID: US6294692B1
- Status: Granted
- Kind: B1
- Application number: 09/460,991
- Filed: 1999-12-15
- Granted: 2001-09-25
- Earliest claimed: 1998-12-30
- Assignees: Isochem
- Inventors: Patricia Hussenet; Philippe Le Goff; Gérard Sennyey; Charles-Henry Vincent
- Web page: https://patentgrep.com/patent/US6294692B1

## CPC

- C07C 231/08: from amides by reaction at nitrogen atoms of carboxamide groups
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

A process for producing N-formylleucine includes reacting leucine with formamide, precipitating the N-formylleucine, once the reaction is complete, at a temperature of approximately 0° to 40° C., by mixing the reaction medium with water and an acid, so that the final pH of the mixture is approximately 2 to 3, wherein the amount of water used in between approximately 1.5 and 5 parts per part by weight of starting formamide.

## Claims

### Claim 1

Process for producing N-formylleucine, comprising:
reacting leucine with formaldehyde in the presence of formic acid;
precipitating the N-formylleucine, once the reaction is complete, at a temperature of approximately 0° to 40° C., by mixing the reaction medium with water and an acid, so that the final pH of the mixture is approximately 2 to 3, wherein the amount of water used when mixing the reaction medium is between approximately 1.5 and 5 parts per part by weight of starting formamide.

### Claim 2 (depends on 1)

The process according to claim 1 wherein the amount of formamide reacted with leucine is less than about 4 mol per mole of leucine.

### Claim 3 (depends on 1)

The process according to claim 1, wherein, in carrying out the precipitation, the water needed for the precipitation is acidified by adding acid before mixing the water with the reaction medium.

### Claim 4 (depends on 3)

The process according to claim 3, wherein before carrying out the precipitation operation, the reaction mixture is diluted with water.

### Claim 5 (depends on 1)

The process according to claims 1 wherein in carrying out the precipitation, water is first mixed with the reaction medium and then the pH of the mixture is brought to and maintained at approximately 2 to 3 by addition of acid.

### Claim 6 (depends on 1)

The process according to claim 1, wherein during the precipitation operation, the pH is, at least at the end of the precipitation, maintained between approximately 2 and 2.5.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the temperature of the precipitation stage is between approximately 5° C. and 20° C.

### Claim 8 (depends on 1)

The process according to claim 1 wherein leucine and formamide are reacted at a temperature of between approximately 80° C. and 110° C.

### Claim 9 (depends on 1)

The process according to claim 1, wherein the reaction is carried out in the presence of approximately 0.1 to 2 mol of formic acid per mole of leucine.

### Claim 10 (depends on 1)

The process according to claim 1, wherein the amount of formamide reacted with leucine is less than 3.5 mole per mole of leucine.
11.The process according to claim 1, wherein the amount of formamide is less than about 4 mole per mole of leucine.