To date, C-20-oxygenated ent-kauranes are the most ones of isolated ent-kaurane diterpenoids. Total synthesis of C-20-oxygenated ent-kauranes is a challenging task due to their high level of oxidation. This review delves into the chemical syntheses and synthetic strategies of three types of C-20-oxygenated ent-kauranes, offering the guidance and reference for the synthesis of other similar compounds.

Abstract

Ent-kaurane diterpenes are a large group of natural products, with more than 1,000 compounds since their discovery. Due to their excellent biological activities and complex polycyclic structures, these compounds have attracted organic synthesis chemists around the world to be devoted to achieve their total synthesis. At present, the isolated C-20-oxygenated ent-kaurane diterpenes are the most abundant of these natural products, reaching more than 350 in number. However, only total syntheses of 3,20-epoxy, 7,20-epoxy and 19,20-lactone ent-kaurane diterpenes have been reported. In this review, we elaborate the synthesis of these three types of C-20 oxygenated ent-kaurane natural products, discuss these synthetic strategies in detail, and provide good guidance and reference for the synthesis of other C-20 oxygenated compounds.