Synthesis and analysis of 2-[211At]-l-phenylalanine and 4-[211At]-l-phenylalanine and their uptake in human glioma cell cultures in-vitro

2-[211At]-l-phenylalanine and 4-[211At]-l-phenylalanine were prepared from the corresponding iodo and bromo derivatives using the Cu+-assisted nucleophilic exchange. 4-[211At]-l-phenylalanine was additionally prepared by destannylation of the BOC-derivatized 4-tributylstannyl-l-phenylalanine. Radiochemical yields of 2-[211At]-l-phenylalanine and 4-[211At]-l-phenylalanine by nucleophilic exchange were 52–74% and 65–85%. Radiochemical yield of 4-[211At]-l-phenylalanine by electrophilic destannylation was 35–50%. HPLC sequence analysis showed that 2-[211At]-l-phenylalanine followed the halogen sequence (F