Abstract:

The problem 9 of the 54th International Chemistry Olympiad describes the total synthesis of capitulactone which was isolated from a plant called Curculigo capitulate, a Chinese medicinal herb. Isolation and synthesis of Capitulactone were reported by academician Jian-Min Yue of Shanghai Institute of Materia Medica in 2019. This problem comprises of two parts. The first part is the construction of the skeleton of this natural product, and the second part is the introduction of the stereocenter derived from chiral pool D-mannitol. The interesting thing is that the oxidative cleavage of the protected D-mannitol leads to a single chiral product, and the stereocenter remains neatly during all transformations. The fundamental knowledges examined in this problem include a number of classical organic reactions like electrophilic substitution, nucleophilic substitution, oxidation, reduction, cleavage of ester bond, ring-opening of epoxides, and formation of ketals. Furthermore, protection and deprotection of hydroxyl groups are also involved in this problem.

Key words: Capitulactone, Natural products, Total synthesis, Chinese medicinal herbal