The most efficient protecting group method for the synthesis of carboxylic acid derivatives such as esters and amides without affecting the functionality of other groups on the same molecule is the use of tert-butyloxycarbonyl t-Boc or benzyl Bn protecting groups.For carboxylic acids, the tert-butyloxycarbonyl t-Boc group is commonly used as a protecting group. The t-Boc group can be introduced by reacting the carboxylic acid with di-tert-butyl dicarbonate Boc2O in the presence of a base such as triethylamine Et3N . The t-Boc group can be selectively removed under mild acidic conditions e.g., using trifluoroacetic acid, TFA without affecting other functional groups on the molecule.Alternatively, the benzyl Bn group can be used as a protecting group for carboxylic acids. The Bn group can be introduced by reacting the carboxylic acid with benzyl alcohol in the presence of a coupling reagent such as 1-ethyl-3- 3-dimethylaminopropyl carbodiimide EDC or N,N'-dicyclohexylcarbodiimide DCC . The Bn group can be selectively removed under hydrogenation conditions e.g., using palladium on carbon as a catalyst and hydrogen gas without affecting other functional groups on the molecule.Both t-Boc and Bn protecting groups are widely used in organic synthesis due to their ease of introduction and removal, as well as their compatibility with a wide range of other functional groups. The choice between these two protecting groups depends on the specific requirements of the synthetic route and the compatibility of the protecting group with other functional groups and reaction conditions.