Has been used, in the presence of pyridine, to protect OH groups as mesitoate esters, very stable to base hydrolysis: J. Am. Chem. Soc., 91, 4318 (1969). The group can be removed reductively, e.g. with LiAlH4: J. Chem. Soc. (C), 2944 (1971), or AlH3: J. Org. Chem., 57, 3431 (1992).