Polyol synthesis is the chemical construction of an organic molecule bearing two or more hydroxyl groups, with control of their positions and, when relevant, relative and absolute configurations. The concept includes carbon–carbon bond-forming routes that generate alcohols, stereoselective reduction of hydroxy carbonyl compounds, epoxide opening, dihydroxylation, hydroboration–oxidation, and iterative homologation of oxygenated fragments. For 1,3-diols and extended 1,3-polyols, syn and anti relationships are commonly established by catalyst-controlled carbonyl addition or by diastereoselective reduction of β-hydroxy ketones ^[1][2]. Cascade strategies can create several carbon–carbon bonds and alcohol stereocenters in one sequence while remaining polyol synthesis because the polyhydroxy product is the target ^[3]. The term excludes the materials-science 'polyol process', in which a polyol is a solvent and reducing agent for metal nanoparticles rather than the compound being synthesized. It also excludes monohydric alcohol synthesis and mere extraction of naturally occurring polyols.