For deprotection (regeneration of the alcohol)
* Aqueous base (pH >9)
* Aqueous acid (pH <2), may have to be heated
* Anhydrous base such as sodium methoxide in methanol. Very useful when a methyl ester of a carboxylic acid is also present in the molecule, as it will not hydrolyze it like an aqueous base would. (Same also holds with an ethoxide in ethanol with ethyl esters)