The present invention provides compounds, and methods for producing compounds having the structure:wherein A is a first polypeptide component of the compound； wherein C is a second polypeptide component of the compound, which polypeptide component comprises consecutive amino acids which (i) are identical to a stretch of consecutive amino acids present in a chain of an F<；sub>；c<；/sub>；domain of an antibody； (ii) bind to an F<；sub>；c<；/sub>；receptor； and (iii) have at their N-terminus a sequence selected from the group consisting of a cysteine, selenocysteine, CP, CPXCP (where X = P, R, or S), CDKTHTCPPCP, CVECPPCP, CCVECPPCP and CDTPPPCPRCP, wherein B is a chemical structure linking A and C； wherein the dashed line between B and C represents a peptidyl linkage； wherein the solid line between A and B represents a nonpeptidyl linkage comprising the structure:
