(S)-2-((tert-Butoxycarbonyl)amino)-3-hydroxypropanoic acid hydrate, commonly known as Boc-L-serine hydrate, is a protected derivative of the natural amino acid L-serine. Its structure features a tert-butoxycarbonyl (Boc) group protecting the alpha-amino group and a free carboxylic acid, with the hydroxyl side chain remaining unblocked. The compound exists as a hydrate, typically containing one molecule of water. This compound is primarily utilized as a key building block in solid-phase peptide synthesis (SPPS) and solution-phase organic synthesis. The Boc group serves as a temporary protecting group that can be selectively removed under acidic conditions (e.g., TFA), allowing for the stepwise construction of peptides. It is also a fundamental intermediate in the preparation of more complex serine derivatives, including phosphoserine, glycosylated serine, and various modified amino acids for medicinal chemistry and biochemical research. As a protected amino acid, it is a staple reagent in pharmaceutical research for synthesizing peptide-based drugs, enzyme inhibitors, and biologically active molecules. Its high enantiomeric purity ensures the stereochemical integrity of the final products. The compound is typically stored at 2-8буC to maintain stability and prevent degradation.