The key building block 4 was isolated as a "side-product" of its cis-isomer in our previous report. Compounds 5a and 5b were synthesized starting from 3,5-dibromo-2,6dimethylphenol via multiple steps involving alkylation, bromination, hydrolysis, oxidation, and Wittig reaction (Scheme S1 in Supplementary Information). The Suzuki coupling reactions between 4 and 5a/5b in dilute solutions gave macrocycles 3a/3b in 21%/20% yield after purification by preparative GPC. The 1 H NMR spectra of 3a/3b recorded in CD2Cl2 indicated a highly symmetrical structure at room temperature (Fig. , S53 in Supplementary Information). Subsequent Bi(OTf)3-mediated cyclization reaction of 3b afforded the double-stranded nanobelt 2b in 63% yield. However, the same reaction on 3a yielded a poorly soluble nanobelt 2a, leading to less than 6% isolated yield. Nevertheless, single crystals of 2a suitable for X-ray crystallographic analysis were successfully obtained at this stage, which clearly confirmed by triply twisted Möbius band structure (see below). Finally, oxidative dehydrogenation of 2b by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dioxane at 125 o C after 5 days gave the fully π-conjugated MCNB 1 in 28% isolated yield. Compound 1 has moderate solubility in THF and is stable under the ambient conditions. Its structure was unambiguously confirmed by X-ray crystallographic analysis, NMR, and high-resolution mass spectrometry (see Supplementary Information). The racemic isomers of 2b and 1 were successfully resolved by chiral HPLC, which allowed us to investigate their chiroptical properties.