The limits of flexibility of the carbyne chain are illustrated by a synthetic polyyne with a backbone of 8 acetylenic units, whose chain was found to be bent by 25 degrees or more ( about 3 degrees at each carbon ) in the solid state, to accommodate the bulky end groups of adjacent molecules.
12.
First stereoselective synthesis was reported by K . C . Nicolaou, more specifically, Sporolide B, through a highly stereoselective and convergent strategy that involves two important cycloaddition reactions : a thermally induced intramolecular [ 4 + 2 ] cycloaddition reaction involving an o-quinone and a tetrasubstituted olefin to form the macrocyclic structure of the molecule, and a ruthenium-catalyzed, intermolecular [ 2 + 2 + 2 ] cycloaddition reaction between two acetylenic units.
