Purification of L-tryptophan in 100 minutes

[Hailstorm]

This is only indirectly related to DMT, but some may still find it useful. No synthesis talk, please - the forum rules impose a limit on how far this thread can go.

Based on the following patents:
https://patentimages.storage.googleapis.com/b2/06/04/f6d002ab7a8532/US5057615.pdf (English)
http://patents.su/2-1152952-sposob-kristallizacii-triptofana.html?do=download (Russian)
https://patentimages.storage.googleapis.com/9e/fd/f1/944c64f3727bbc/CN104926709A.pdf (Chinese)

You can purify L-tryptophan to >99% by recrystallizing it in aqueous acetic acid.

A minimum amount 5% to 25% solution (percent weight) of acetic acid in distilled water is used - just enough to dissolve all the L-tryptophan when the solution is hot. The weight of the glacial acetic acid in the solution should be equal or greater than the weight of L-tryptophan.

0.5% (of the L-tryptophan weight) of vitamin C or E can optionally be added to prevent oxidative degradation of the L-tryptophan in the acid. The anti-oxidant is not necessary if the acid concentration is 20% or lower.

The solution is heated with stirring to 80-95°C until complete dissolution of the L-tryptophan is observed. Any insoluble impurities are filtered out via hot filtration. The saturated solution is allowed to cool, slowly, to 30°C (room temperature) and remain at that temperature. This initial cooling period should take at least 75 minutes. The solution is then placed into a refrigerator for at least 25 more minutes to cool down to 1-5°C.

The purified L-Tryptophan is filtered out of the ice-cold solution, washed in ice-cold distilled water to remove any residual acetic acid, and dried to constant weight.

 

[Hailstorm]

So, for 10g of L-tryptophan, at least 200g of 5% distilled vinegar will be required (or 10g of glacial acetic in 40g+ of distilled water) plus (optionally) 50mg of vitamin C.

The solution is heated on a magnetic hotplate with stirring to 85°C; more acidic water may be added to dissolve the L-tryptophan completely. The liquid should be fully transparent. If any insoluble impurities remain, the solution is heated up more and then quickly filtered before it cools down.

During the following 75 minutes the solution is allowed to cool down to 30°C and stay at 30°C. It is then moved to a refrigerator for 25 more minutes. Longer cooling times will result in larger and purer crystals but may increase the risk of oxidation.

Quick cold filtration under vacuum, followed by washing in cold distilled water (until the L-tryptophan no longer smells like vinegar), followed by drying, complete the process.

 

[Ferrum]

Thank you . I know a very good use for this.

 

[blue.magic]

Thank you!

I have struggled to recrystallize tryptophan from just water with little success (it really does not want to, even from heavily supersaturated solution).

My tryptophan has 1% taurine added and taurine is hard to remove by washing - I found no common solvents to separate the two compounds, so recrystallization was the only option.

 

[Prima Materia]

Have any observations been made that cleaning up the stourebought tryptophan actually helps in getting better results via decarboxylation process?
I've been trying to get it to work but with not much success so far, therefore the clean-up seems like a possible improvement.

 

[Transform]

Have any observations been made that cleaning up the stourebought tryptophan actually helps in getting better results via decarboxylation process?
I've been trying to get it to work but with not much success so far, therefore the clean-up seems like a possible improvement.

It would seem desirable to minimise impurities of any kind here. Each impurity is just one more possible way that losses might get incurred, and none of them is likely to bring about an improvement in the results.

The re-x solvent (essentially, concentrated vinegar) is freely available to the extent that I'm thinking of trying the procedure myself. Now, where did I put that tryptophan, hm?

In short, this is easy enough and the likelihood of benefit is srgnificant enough that it would be almost silly not to try it, especially if you've been struggling with the decarboxylation so far.

 

[Prima Materia]

It would seem desirable to minimise impurities of any kind here. Each impurity is just one more possible way that losses might get incurred, and none of them is likely to bring about an improvement in the results.

The re-x solvent (essentially, concentrated vinegar) is freely available to the extent that I'm thinking of trying the procedure myself. Now, where did I put that tryptophan, hm?

In short, this is easy enough and the likelihood of benefit is srgnificant enough that it would be almost silly not to try it, especially if you've been struggling with the decarboxylation so far.

Thanks for the heads up. Will report here when I get to the re-x. The really clean grade tryptophan is too expensive to work with, therefore the clean up makes total sense.

 

[Prima Materia]

A patent on the topic seems to be available:


PROCESS FOR PURIFYING TRYPTOPHAN:

ABSTRACT:
A process for purifying tryptophan is disclosed. In the process of the present invention, tryptophan is recrystallized in water-containing acetic acid. By the process of the present invention, tryptophan with high purity may be obtained with high yield without condensation or neutralization.

 

[blig-blug]

A patent on the topic seems to be available:


PROCESS FOR PURIFYING TRYPTOPHAN:

ABSTRACT:
A process for purifying tryptophan is disclosed. In theprocess of the present invention, tryptophan is recrystallized in water-containing acetic acid. By the process of the present invention, tryptophan with high puritymay be obtained with high yield without condensation or neutralization.

https://patentimages.storage.googleapis.com/b2/06/04/f6d002ab7a8532/US5057615.pdf (English)

 

[Transform]

A patent on the topic seems to be available:


PROCESS FOR PURIFYING TRYPTOPHAN:

ABSTRACT:
A process for purifying tryptophan is disclosed. In the process of the present invention, tryptophan is recrystallized in water-containing acetic acid. By the process of the present invention, tryptophan with high purity may be obtained with high yield without condensation or neutralization.

The fact that recrystallising a common amino acid in an even more common dilute acid is considered worthy of a patent seems… remarkable. Was this patent actually granted?

 

[blig-blug]

The fact that recrystallising a common amino acid in an even more common dilute acid is considered worthy of a patent seems… remarkable. Was this patent actually granted?

Looks like yes, it was granted in several countries. It appears to have expired in most of them, although for a couple of them no expiration is mentioned: US5057615A - Process for purifying tryptophan - Google Patents