9-Fluorenylmethyl Chloroformate [N-Protecting Agent for Peptides Research]

Used Chemicals

• 9-Fluorenylmethyl Chloroformate (= Fmoc-Cl) [F0197]
• H-DL-Ala-OMe·HCl [A2446]
• Na₂CO₃ [S0560]
• 1,4-Dioxane

Procedure

To a solution of H-DL-Ala-OMe·HCl (195 mg, 1.40 mmol) in 1,4-dioxane (1.8 mL) were added 10% sodium carbonate aq. (1.8 mL, 2.2 eq.), Fmoc-Cl (337 mg, 1.4 mmol) in 1,4-dioxane (3.6 mL) at 0 °C and the mixture was stirred at room temperature for one day. The mixture was diluted with water (5 mL) and extracted with dichloromethane (30 mL). The organic layer was washed with 1 mol/L HCl aq. (30 mL), water (30 mL), and brine (30 mL), dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography (on silica gel, ethyl acetate:hexane = 0:100 - 10:90 - 20:80) to give Fmoc-DL-Ala-OMe as a white solid (445 mg, 98% yield).

Experimenter’s Comments

The reaction mixture was monitored by TLC (ethyl acetate:hexane = 1:1, Rf = 0.55).
Peaks of the rotamer was observed on NMR. Below analytical data shows the major peaks only.

Analytical Data

Fmoc-DL-Ala-OMe

¹H NMR (270 MHz, CDCl₃); δ 7.76 (d, J = 7.6 Hz, 2H), 7.59 (brd, J = 6.8 Hz, 2H), 7.40 (t, J = 7.0 Hz, 2H), 7.31 (dt, J = 0.8, 7.3 Hz, 2H), 5.37 (brd, 7.0 Hz, 1H), 4.45-4.34 (m, 3H), 4.22 (t, J = 7.0 Hz, 1H), 3.76 (s, 3H), 4.43 (d, J = 6.8 Hz, 3H).

Other Reference

• A Prodrug Resistance Mechanism Is Involved in Colibactin Biosynthesis and Cytotoxicity
• C. A. Brotherton, E. P. Balskus, J. Am. Chem. Soc. 2013, 135, 3359.

References

• V. Perron, S. Abbott, N. Moreau, D. Lee, C. Penney, B. Zacharie, Synthesis 2009, 283.