Used as a key reagent in organic synthesis, particularly in Wittig reactions to introduce the tert-butoxycarbonylmethyl group. This enables the formation of α,β-unsaturated esters with protected carboxylic acid functionalities, which are valuable intermediates in the synthesis of complex molecules such as pharmaceuticals and natural products. The tert-butyl ester group can be easily deprotected under mild acidic conditions, allowing for further functionalization downstream. Its stability and reactivity profile make it suitable for multi-step syntheses where selective transformations are required.