Synthesis
The general procedure for the synthesis of Fmoc-N-methyl-L-alanine from the compound (CAS: 83999-95-5) was as follows: paraformaldehyde (4.0 g, 133 mmol) and p-toluenesulfonic acid (0.5 g, 13.3 mmol) were added to a suspension of Fmoc-L-alanine (6.2 g, 19.9 mmol) in toluene (400 mL). The mixture was refluxed for 30 min to remove azeotropic water. The solution was cooled, washed with 1 M aqueous NaHCO3 (2 x 100 mL) and dried with Na2SO4. Subsequently, the solution was concentrated in vacuum to give a white solid. The above oxazolidinone was dissolved in chloroform (75 mL) and trifluoroacetic acid (75 mL) and triethylsilane (7.2 mL, 44.8 mmol) were added. The reaction mixture was stirred at room temperature for 10 hours and then concentrated under vacuum. The resulting oily substance was dissolved in dichloromethane and the concentration was repeated three times. After standing, the oily substance crystallized. The crystals were redissolved in ether and concentrated. Finally, the collected white solid was washed with 5% ether/hexane and dried to give the product (6.1 g, 94% yield).
References
[1] Tetrahedron Letters, 2011, vol. 52, # 30, p. 3872 - 3875
[2] European Journal of Organic Chemistry, 2013, # 21, p. 4509 - 4513
[3] Journal of Organic Chemistry, 2005, vol. 70, # 17, p. 6918 - 6920
[4] Tetrahedron Letters, 2006, vol. 47, # 11, p. 1691 - 1694
[5] Tetrahedron Letters, 2014, vol. 55, # 44, p. 6109 - 6112
