title: Atropisomerism in 1,5-bridged calix[8]arenes.
abstract: [structure: see text] The first example of two discrete calix[8]arene conformational isomers, 2 and 2a, has been obtained by exhaustive benzylation of 1,5-tetramethylene-bridged calix[8]arene 1. It is demonstrated, with the aid of X-ray crystallography, that these atropisomers have two 3/4-cone halves oriented syn or anti with respect to the bridge/bridgeheads moiety. VT NMR studies indicate that the tert-butyl-through-the-annulus inversion is inhibited in 1, while groups larger than n-hexyl or benzyl are required for curtailing the O-through-the-annulus route.
authors.affiliation: Istituto di Chimica Biomolecolare - Sezione di Catania, CNR, Via del Santuario 110, I-95028 Valverde (CT), Italy.
authors.forename: Grazia M L
authors.initials: GM
authors.lastname: Consoli
authors.forename: Francesca
authors.initials: F
authors.lastname: Cunsolo
authors.forename: Corrada
authors.initials: C
authors.lastname: Geraci
authors.forename: Enrico
authors.initials: E
authors.lastname: Gavuzzo
authors.forename: Placido
authors.initials: P
authors.lastname: Neri