Evaluation of an approach for the synthesis of C2 alkylated gramines

A simple alkylation at the C2 position of N-protected gramines under relatively mild reaction conditions was investigated. The designed transformation involves the reaction of N-protected gramines with n-BuLi and a variety of alkyl halides to produce C2, N’-dialkylated gramine salts in moderate to high yield. We demonstrated that both gramine’s methylene N and directing groups such as N-Boc of indole cooperate to facilitate C2 lithiation and provide the highest conversion to the product.