Synthesis of Gem-Dimethyl Bicyclic [3.1.0] Proline as an Antiviral Drug Intermediate

: Gem-dimethyl bicyclic [3.1.0] proline, an azadicyclohexane derivative, constitutes a prevalent skeleton structure in drugs, which serves an important role in the synthesis of antiviral drugs, such as Nirmatrelvir, Boceprevir, Narlaprevir, etc. This study offers a comprehensive overview of the documented synthetic strategies for gem-dimethyl bicyclic [3.1.0] proline methyl ester and delves into the application characteristics of each synthetic strategy. These synthetic approaches can be divided into three major types: the first synthetic method uses proline derivatives as the starting material, the second one uses cyclopropane derivatives as the starting material, and the third one uses the bicyclic skeleton as the starting material. Of these strategies, the third method stands out as the most extensively adopted.