Neither 3: 5-dinitro-(I; R= NO,, R'= NH,) nor 3: 5-di-iodo-4-p-methoxyphenoxy-L- phenylalanine (I; R= I, R'= NH,) could be converted into the corresponding a-halogeno-acid (R'= C1 or Br) by treatment with the nitrosyl halide. However, 3: 5-dinitro-~-tyrosine reacted
