A large calixarene-like metacyclophane, 4′,9′,4″,9″-tetra-tert-butyl-1′,6′,1″,6″-tetramethoxy-2,5-dioxa[3.3]metabiphenylophane, was synthesized by an intermolecular condensation reaction of its corresponding bischloromethyl-biphenyl and bishydroxymethyl-biphenyl precursors. After molecular characterization by 1H NMR spectroscopy and mass spectrometry, the compound generated single crystals by recrystallization from a dichloromethane/hexane mixture, facilitating an exact conformational determination via X-ray diffraction analysis. The crystal was found to belong to the monoclinic space group with cell parameters a = 19.908(2)？？, b = 9.7193(11)？？, c = 23.350(3)？？, β = 109.594(1)°, and ？g/cm3 at 90？K. The compound adopted quite strained 1,2-alternate-like conformations because its biphenyl parts displayed large dihedral angles and rigidity. The crystal did not incorporate any solvent molecule but its molecular cavity and crystal space were effectively filled by the substituents. 1. Introduction Calixarenes are cyclic compounds consisting of aromatic rings and methylene bridge chains. In search for novel supramolecular hosts, numerous efforts have been deployed to decorate the upper or lower rim of calixarenes with various functional groups [1–3]. However, the nature of their cyclic skeleton clearly plays a central role in their remarkable performance as host molecules. Members of the metacyclophane family [4–8], calixarenes, are readily obtained by base-assisted condensation of tert-butylphenol and formaldehyde into methylene-based bridges exclusively. In addition, several calixarene analogues such as []metacyclophanes containing oxygen [9, 10] or nitrogen [11, 12] instead of methylene groups in their bridges have been prepared. Cyclic compounds such as calix[4]arenes and large metacyclophanes present various conformations derived from the orientations of the aromatic parts [13]. In addition, the crystal structures of several cyclophanes have been reported using an alternative synthetic pathway [14] and cesium ion template effect [15–19]. Although large metacyclophanes comprising ether bridges and biphenyl units have been synthesized and their host-guest properties were reported [20, 21], their structures in the crystals were not determined. In this study, we report the synthesis of “oxametabiphenilophanes,” a new class of metacyclophanes that incorporate oxygen atoms in bridges and two biphenyl parts thus giving rigidity to the molecules (Scheme 1). A precursor mixture of bischloromethyl-biphenyl and bishidroxymethyl-biphenyl reacted under alkaline
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