Metathesis-Based Stapling of a Pyridine–Acetylene–Phenol Oligomer Having Alkenyl Side Chains after Intermolecular Templation by Native Saccharides

A nonameric (pyridine–acetylene–phenol–acetylene)₄–pyridine oligomer formed a helical structure by intermolecular templation with a hexose such as d-glucose associated by the means of solid–liquid extraction. Subsequent treatment by 2nd generation Grubbs catalyst stapled the helix by double-cross-linking among four 3-butenyloxy side chains on the pyridine units. The stapling never proceeded without the templation. The resulting double-bridged helix could be asymmetrized to show typical Cotton effects, not only by the strong binding with octyl hexosides in a DCE solution but also by the solid–liquid extraction of native hexoses into an organic phase. A chiral memory effect of the double-bridged helix was studied by guest exchange using equimolar d- and l-glucosides, and the half-time of racemization of the helix was estimated to be 1 min.