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TCI Practical Example: tert-Butyl Esterification Utilizing the Isourea Derivative

We are proud to present the tert-butyl esterification with easy handling.

Used Chemicals

• Boc-Ser-OH [B1637]
• O-tert-Butyl-N,N'-diisopropylisourea [B4178]
• Dichloromethane

Procedure

To a solution of Boc-Ser-OH (0.94 g, 4.6 mmol) in dichloromethane (10 mL) O-tert-Butyl-N,N'-diisopropylisourea (3.3 mL, 14.0 mmol) was added dropwise over 5 min at 3 °C then stirred overnight at room temperature under nitrogen atmosphere. To the reaction mixture hexane (10 mL) was added then filtered through celite and the solvent was removed under reduced pressure. The residue was purified by column chromatography (1:1 = ethyl acetate:hexane on silica gel), giving Boc-Ser-OtBu as a white solid (0.59 g, 50% yield).

Experimenter's Comments

The reaction mixture was monitored by TLC (hexane : ethyl acetate = 1:1, Rf = 0.60).

Analytical Data

Boc-Ser-OtBu

¹H NMR (400 MHz, CDCl₃); δ 5.57–5.30 (m, 1H), 4.36–4.15 (m, 1H), 3.97–3.79 (m, 2H), 2.57–2.34 (m, 1H), 1.51-1.41 (m, 18H).

¹³C NMR (101 MHz, CDCl₃); δ 169.9 (2 C), 82.8, 80.3, 64.3, 56.5, 28.4 (3 C), 28.1 (3 C).

Lead Reference

• L-Type amino acid transporter 1 activity of 1,2,3-triazolyl analogs of L-histidine and L-tryptophan
• C. Hall, H. Wolfe, A. Wells, H.-C. Chien, C. Colas, A. Schlessinger, K. M. Giacomini, A. A. Thomas, Bioorg. Med. Chem. Lett. 2019, 29, 2254.

Other References

• Esterification and Alkylation Reactions Employing Isoureas
• L. J. Mathias, Synthesis 1979, 8, 561.