Subsequently, the C-H biarylation of N-phthaloyl-L-alanine (19) was attempted. With the recent advancements in C-H activation, numerous C-H arylation reactions utilizing Pdcatalyzed L-alanine derivatives and aryl iodides have been reported. The most common approach in C-H arylation using L-alanine derivatives as substrates involves employing aminoquinoline as a directing group. 7 However, aminoquinoline often presents challenges due to its multi-step deprotection process, which is generally time-consuming and problematic for substrates sensitive to base and oxidation. 7c, 7e, 9 In our preliminary investigations, we attempted the C-H biarylation using an L-alanine derivative containing aminoquinoline as the directing group, along with aryl iodide 18, following the reported conditions. The desired C-H biarylation was observed to proceed; however, the deprotection of aminoquinoline required two steps (Boc protection and hydrolysis by LiOH/H2O2), resulting in a significantly low yield (21% for three steps from the C-H biarylation). Detailed investigation of the by-products revealed that the acetyl group on the biaryl moiety was deprotected during the Boc-aminoquinoline deprotection using LiOH/H2O2 conditions. Furthermore, the resulting aniline was oxidized by H2O2, leading to the formation of a complex mixture. Other conditions for aminoquinoline removal were also attempted but proved to be unsatisfactory in terms of both step count and yield.