A process is provided for preparing a conjugate of Formula (I-A) or (I) comprising a polypeptide containing n number of tyrosine units, where n is an integer greater than or equal to 1, dispersed within the amino acid chain having and amino terminus end (A1) and an acid terminus end (A2) of the protein or polypeptide and having a weight average molecular weight equal to or greater than 10,000 Daltons (10 kDa), wherein the conjugate comprises a number m of tyrosine conjugates (modified tyrosine residues) as depicted in Formula (I-A) or (I), where m is at least one and is less than or equal to n: where X, Lg, L and R are as defined herein.