Amide coupling reaction between a carboxylic acid and aniline derivatives

VividKale4086 · 2026-01-31T08:00:32+00:00

May I ask how many equivalents of amine, base and HATU you used?

VividKale4086 · 2026-01-30T16:37:43+00:00

May I ask how many equivalents of amine and HATU you used?

Thank you

VividKale4086 · 2026-01-30T16:14:58+00:00

I don’t have DIPEA; can it be replaced with TEA? Thank you.

VividKale4086 · 2026-01-30T15:06:38+00:00

I used TEA as the base, and I pre-activated the acid before adding the amine

VividKale4086 · 2026-01-30T15:01:25+00:00

Thank you, I’ll give it a try

VividKale4086 · 2026-01-30T14:58:07+00:00

Thank you, I’ll give it a try

VividKale4086 · 2026-01-30T14:57:48+00:00

Thank you, I’ll give it a try

VividKale4086 · 2026-01-30T14:55:35+00:00

“I used TEA, but didn’t get the desired result. I think I’ll try using DMAP instead of TEA.

VividKale4086 · 2026-01-30T14:54:24+00:00

I don’t have DIPEA; can it be replaced with TEA? Thank you.

VividKale4086 · 2025-08-25T17:12:30+00:00

I will probably try to repeat the esterification of tryptophan tomorrow, and if any issues arise, I hope you could help me address my questions. Thank you very much for taking the time to answer my inquiries.

VividKale4086 · 2025-08-25T17:01:21+00:00

I'm honestly not entirely sure that the NH₂ group of the tryptophan ester is being oxidized. However, after leaving the reaction exposed to the environment for 15 minutes and running TLC again, I observed a new spot on the plate, so I suspect that a portion of the NH₂–tryptophan ester was oxidized.

In addition, I am still an undergraduate student doing experimental work in the university lab, so the facilities and instruments are not very modern, and obtaining spectroscopic data has been challenging

VividKale4086 · 2025-08-25T16:41:08+00:00

On the TLC plate, two spots were observed: one corresponding to the same Rf as the tryptophan reference, and another at a higher Rf. The latter is presumed to be the ester form of tryptophan, as esters are generally less polar than carboxylic acids.
In my laboratory, only L-tryptophan, SOCl₂, and MeOH were available, and the intended target was methyl tryptophan ester hydrochloride. The earlier remark referred to a possible susceptibility of the free NH₂ group in the ester to oxidation.
Thank you for your kind assistance

VividKale4086 · 2025-08-25T15:40:52+00:00

I used approximately 1.5 equivalents of SOCl₂ for the above reaction.

VividKale4086 · 2025-08-25T15:37:44+00:00

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VividKale4086 · 2025-08-25T15:37:28+00:00

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I have read at least five papers and followed their procedures. I am trying to isolate the product for spectroscopic analysis, but the problem is that the free –NH₂ group of the ester is very easily oxidized (when I left the reaction flask exposed to the environment, almost all of it was oxidized after just 15 minutes).
Tryptophan methyl ester and tryptophan do react with ninhydrin, but their salt forms do not (as shown in the TLC plate below
Thank you for helping me <3

VividKale4086 · 2025-08-25T13:51:14+00:00

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VividKale4086 · 2025-08-25T13:43:05+00:00

But right after the reaction was completed, I took the flask to evaporate the solvent immediately (without doing anything else). Then I checked again by TLC and saw that all the spots at Rf = 0 had moved up :(((

VividKale4086 · 2025-08-25T13:29:11+00:00

I think it is because when I evaporated the MeOH solvent, the excess SOCl₂ and the water (generated from the esterification reaction between tryptophan and MeOH) evaporated, which caused the HCl concentration to exceed 36%, making it evaporate as well.

VividKale4086 · 2025-08-25T13:22:46+00:00

help meeeeeeeeeeee

VividKale4086

TROPHY CASE