The present invention provides intermediate compounds containing a triazine or trans-cyclooctene group, useful in the preparation of compounds having the structure: A-B-----Zwherein A is a biologically active structure of the compound； wherein Z is a protein component of the compound, which protein component comprises one or more polypeptides, wherein at least one of the one or more polypeptides comprises consecutive amino acids which (i) are identical to a stretch of consecutive amino acids present in a chain of an Fc domain of an antibody； (ii) bind to an Fc receptor； and (iii) have at their N-terminus a sequence selected from the group consisting of a cysteine or selenocysteine； wherein the dashed line between B and Z represents a peptidyl linkage； and wherein the solid line between A and B represents a nonpeptidyl linkage.
