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Deprotection of methyl (2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoate;
(2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoic acid
acid
(2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoic acid

SyntheticPage 927
Submitted Apr 29, 2020, published May 04, 2020
Bart Dietrich (bart.dietrich@yahoo.co.uk)
A contribution from Dave Adams Group, Glasgow


			Reaction Scheme: Deprotection of <a target=methyl (2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoate">

Chemicals Used

methyl (2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoate
Lithium hydroxide anhydrous (Alfa)
Tetrahydrofuran HPLC grade (Fisher)
Water (tap)

Procedure

To a suspension of methyl (2S)‐2‐[2‐(9H‐carbazol‐9‐yl)acetamido]propanoate (5.02 g, 16.2 mmol) in tetrahydrofuran (50 mL) was added a solution of lithium hydroxide (4 eq, 1.55 g) in water (50 mL). The reaction mixture turned clear after about 10 minutes, then a precipitate began to develop again which had become thick after 90 minutes. The reaction mixture was stirred another 90 minutes. TLC indicated the absence of starting material. The reaction mixture was poured into 1M hydrochloric acid (200 mL) and stirred vigorously for 1 hour. The precipitate was then filtered off and washed with plenty of water in the filter. Suction drying then drying by azeotropic distillation with acetonitrile afforded the title compound as a white solid (4.58 g, 95 %).

Author's Comments

  • Hydrolysis of the amide bond may become a problem if the reaction is much more concentrated or run for a much longer time.
  • Hydrated forms of lithium hydroxide may be used: the weight required needs to be recalculated in that case.

Data

dH (400 MHz, DMSO-d6) 12.64 (1H, br s, COOH), 8.73 (1H, d, J 7.44, NH), 8.14 (2H, d, J 7.60, HAr), 8.24 (2H, d, J 8.24, HAr), 7.42 (2H, ddd, J 8.20, 7.12, 1.12, HAr), 7.22-7.18 (2H, m, HAr), 5.12 (1H, d, J 17.21, NCHaHb), 5.02 (1H, d, J 16.81, NCHaHb), 4.25 (1H, pseudo-quintet, J 7.30, CH*), 1.33 (3H, d, J 7.28, CH3). dC (100 MHz, DMSO-d6) 173.89 and 167.29 (C=O), 140.64, 125.62, 122.22, 120.10, 118.96, and 109.40 (CAr), 47.67 (CH*), 45.28 (NCH2), 17.36 (CH3). HRMS (ESI) m/z: [M+Na]+ calcd for C17H16N2NaO3 319.1053; found 319.1047.


Supplementary Information

Proton NMR, DMSO-d6 (fd-005 1h.png)
Carbon NMR, DMSO-d6 (fd-005 13c.png)

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Get structure file (.cdx, .sk2, .mol)

Keywords: amides, amino acids, aromatics/arenes, CarbA, carboxylic acids, deprotection, gelator, gels

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