General procedure for the synthesis of methyl (R)-2-((tert-butoxycarbonyl)amino)-3-iodopropionate from methyl Boc-L-serinate: a mixture of triphenylphosphine (131 g, 0.500 mol) and imidazole (34 g, 0.50 mol) in dichloromethane (600 mL) was cooled to 0 °C and over 0.5 h iodine was added in batches (127 g, 0.50 mol). The cooling bath was removed and the mixture was stirred for 0.5 hours. After cooling the mixture to 0 °C again, a solution of methyl (R)-2-((tert-butoxycarbonyl)amino)-3-hydroxypropionate (73 g, 0.33 mol) in dichloromethane (300 mL) was slowly added dropwise. After dropwise addition, the cooling bath was removed and the mixture was warmed to room temperature and stirred for 1.5 hours. The reaction mixture was filtered and the filtrate was concentrated to remove most of the solvent. Methyl tert-butyl ether (400 mL) was added to the residue and filtered to remove triphenylphosphine oxide. The filtrate was concentrated and the residue was purified by rapid column chromatography on silica gel to afford methyl (R)-2-((tert-butoxycarbonyl)amino)-3-iodopropionate (74.0 g, 68% yield) as a colorless solid.
[1] Journal of Organic Chemistry, 2009, vol. 74, # 17, p. 6792 - 6796
[2] Organic Letters, 2003, vol. 5, # 24, p. 4599 - 4602
[3] Organic Letters, 2011, vol. 13, # 10, p. 2614 - 2617
[4] Tetrahedron, 2017, vol. 73, # 42, p. 6085 - 6091
[5] Tetrahedron Letters, 2007, vol. 48, # 16, p. 2857 - 2859
