Carboxyl groups can be protected as 2-(trimethylsilyl)ethyl (TMSE) esters by carbodiimide coupling: Helv. Chim. Acta, 60, 2711 (1977); J. Org. Chem., 62, 93 (1997), from the acid chloride in pyridine: Helv. Chim. Acta, 60, 3039 (1977), or refluxing the acid in THF in the presence of TMS chloride: J. Am. Chem. Soc., 106, 3030 (1984). The TMSE protecting group is useful in peptide synthesis. Cleavage is readily effected with TBAF in DMF or DMSO: Helv. Chim. Acta, 60, 2711 (1977); Bioorg. Med. Chem. Lett., 3, 437 (1993).
