Used as a protected form of hydroxyacetic acid (glycolic acid) in organic synthesis, particularly in the construction of complex molecules where selective reactivity is required. The tert-butyldimethylsilyl (TBS) group acts as a protecting group for the hydroxyl functionality, preventing unwanted side reactions during multi-step syntheses. Commonly employed in pharmaceutical and natural product synthesis, it allows for controlled deprotection under mild conditions, such as using fluoride ions, enabling precise functional group manipulation. Its ester moiety can undergo standard transformations such as reduction to alcohols or conversion to amides, making it a versatile building block in medicinal chemistry.