If you are using the search bar function, entering only the name of the amino acid (e.g. “serine”) will yield all products containing the amino acid residue. This will include peptide sequences containing the amino acid as well as other derivatives.
When entering the three-letter code designation, defining both the N- and C-terminus will lead to the desired product as the top result (if the product is available).
Examples: H-Ser-OH, Ac-Leu-OH, Boc-Val-OH
A list of building blocks or products for peptide synthesis are available under “Amino Acid Derivatives and Reagents”.