Steroidal sapogenin-derived chirons: underdeveloped building blocks with methyl-branched chiral centers

Three kinds of chiral lactones with methyl-branched stereocenters were obtained on large scale based on H₂O₂-mediated oxidative degradation of steroidal sapogenins. These chiral lactones are valuable chirons for the total synthesis of bioactive compounds containing methyl-branched chiral centers. This review comprehensively summarizes the synthetic application of the steroidal sapogenin-derived chiral lactones in insect pheromones, complex natural products and pharmaceuticals, with a particular focus on the chirality transfer from chiral lactones to the corresponding motifs of target molecules. We hope these underdeveloped chirons can act as a complement to commonly used methyl-branched chirons such as citronellol and Roche ester, and meet more synthetic applications in the future.