Peter R. Ashton

The self-assembly of [n]pseudorotaxanes

An acyclic oligomeric polyether in which four tetraethylene glycol units are located between five hydroquinol rings, with the two terminal rings carrying benzyl ether groups, self-assembles in solution with one and two molar equivalents of a tetracationic cyclobis(paraquat-p-phenylene) macrocycle to afford, respectively and selectively, a [2]pseudorotaxane and a [3]pseudorotaxane.

The self-assembly of a highly ordered [2]catenane

Template-directed synthesis has been used to construct a [2]catenane in which the two molecular components, the cyclobis(paraquat-p-phenylene) tetracation and 1,5-dinaphtho-38-crown-10, are found to be ordered non-covalently with respect to each other in both the solid (by X-ray crystallography) and solution (by NMR spectroscopy) states and to influence each other to the extent of establishing electrochemical gradients for the stepwise one electron reductions of the two paraquat units.

Complex formation between bisparaphenylene-(3n+ 4)-crown-n ethers and the Paraquat and Diquat dications

U.v. and n.m.r. spectroscopic investigations in solution have been employed to assess the ability of a series (n= 7–12) of bisparaphenylene-(3n+ 4)-crown-n ethers to form stable 1:1 complexes with [Diquat]2+ and [Paraquat]2+ dications; these mappings of molecular recognition are supported by fast atom bombardment mass spectrometry of the 1:1 complexes with both [Diquat][PF6]2 and [Paraquat][PF6]2, and a single crystal X-ray structure analysis of [Diquat·BPP31C9][PF6]2.

The complexation properties of some unnatural and natural macrocyclic trichothecenes

As a result of investigating the complexing properties of a series of novel polyether analogues (3)–(9) of macrocyclic trichothecenes towards alkali metal cations and RNH3+ ions, it has been proposed, with supporting evidence from X-ray crystallography on verrucarin A (1) and fast atom bombardment mass spectrometry of complexes involving (1) and the triacetate (10) of baccharinol B4 (11), that the enhanced biological activities of macrocyclic trichothecenes, such as (1) and (11), compared with non-macrocyclic trichoverroids such as (2), may be a consequence of their abilities to bind to NH3+ ionic sites on proteins, particularly those associated with the 60S ribosomes.