An efficient synthesis of l-3,4,5-trioxygenated phenylalanine compounds from l-tyrosine

A new strategy for the synthesis of l-3,4,5-trioxygenated phenylalanine derivatives from l-tyrosine is developed for the first time. The approach, featuring the transformation of aryl diiodide to bis-phenol via a one-pot procedure including lithiation, boronation, and oxidation, is highly practical. By this robust protocol, N-protected l-3,5-bis(tert-butyldimethylsilyloxy)-4-methoxy-phenylalanine and l-3,4,5-trimethoxy-phenylalanine derivatives were obtained from l-tyrosine in 9 steps with 36-40% overall yields.