The invention relates to an improved process for preparing [(1R), 2S]-2-aminopropionic acid 2-[4-(4-fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[2,1-f][1,2,4]tr- iazin-6-yloxy]-1-methylethyl ester of the formula: ##STR00001## Compound I has been shown to be useful for the treatment of certain types of cancer.