(9H-Fluoren-9-yl)methyl 4-hydroxypiperidine-1-carboxylate is an Fmoc-protected derivative of 4-hydroxypiperidine, commonly used as a building block in organic synthesis. The fluorenylmethyloxycarbonyl (Fmoc) group protects the piperidine nitrogen, enabling its incorporation into peptide chains or other complex molecules via solid-phase peptide synthesis (SPPS). The free hydroxyl group at the 4-position allows for further functionalization, such as esterification or ether formation, before deprotection of the Fmoc group under mild basic conditions (e.g., with piperidine). This orthogonality makes it valuable for constructing modified peptides, peptidomimetics, and pharmaceutical intermediates with precise control over reactivity.