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The cover picture shows the window-like structure of [5.5.6.6]fenestranes as an outlook onto the slopes of the Teutoburger Wald near Bielefeld, Germany.
In an attempt to approach the – yet hypothetical – fully unsaturated tetrabenzo[5.5.5.5]fenestrene ("fenestrindene", top left in the clouds), bearing a flattened tetracoordinate carbon atom, via a – likewise hypothetical – phenanthro-annellated [5.5.5.5]fenestrane (top right), two novel diastereomeric [5.5.6.6]fenestranes were synthesized: The all-cis-benzodiphenanthro[5.5.6.6.]fenestrane ketone (bottom left) and the corresponding cis,cis,trans,cis isomer (bottom right). The cyclization reactions giving rise to these complex fenestrane frameworks involve unexpected stereoselectivity and ring sizes, as discussed in the article by D. Kuck et al. on p. 53 ff.