Interleukin-6 (IL-6), a multifunctional cytokine, is an attractive therapeutic target for immunological and inflammatory diseases. The author investigated the chemical synthesis of IL-6 and its enantiomer (d-IL-6) using a sequential N-to-C native chemical ligation strategy. Solubilizing Trt-K10 tags, which were used to facilitate the synthesis of full-length IL-6 protein from six peptide segments, improved the intermediate solubility and served as protecting groups during the metal-free desulfurization. Synthetic l-IL-6 and recombinant l-IL-6 exhibited identical structural and binding properties. The symmetrical binding property of d-IL-6 was also demonstrated by functional analysis using IL-6-binding peptides. The resulting functional d-IL-6 was employed to screen a phage-displayed antibody fragment library, leading to the identification of several d-IL-6-binding sequences with high homology.