Synthesis of bis-peptides attached on poly[n]norbornene molecular scaffolds with well-defined relative positions and distances

Molecular tweezers with a rotationally restricted linker and freely rotating porphyrin moieties

The effect of the degree of conformational rigidity and/or flexibility on preorganisation in artificial molecular receptors continues to be actively explored by supramolecular chemists. This work describes a bis-porphyrin architecture, linked via a rigid polycyclic backbone, in which a sterically bulky 2,3,5,6-tetramethylphenyl diimide core restricts rotation to afford two non-interconvertible tweezer conformations; syn- and anti-. After separation, the host-guest chemistry of each conformation was studied independently. The difference in host geometry allows only the syn-conformation to form a strong 1 : 1 bis-porphyrin complex with the diamino ligand 1,4-diazabicyclo[2.2.2]octane (DABCO) (K11 = 1.25 × 108 M-1), with the anti-conformation adopting a 2 : 2 sandwich complex with DABCO (K22 = 5.57 × 1017 M-3).

Alternative Access to Functionalized 2,8-Ethanonoradamantane Derivatives

7a-(Methoxycarbonyl)-N-methyl-1,3a,5,6,7,7a-hexahydro-4H-1,4,6-(epiethane[1,1,2]triyl)indene-4,9-dicarboximide has been prepared through a modification of a previous synthetic sequence, in which the benzyloxymethyl hydroxyl protecting group has been replaced by methoxymethyl, to avoid the apparent formation of a benzyl ester derivative as a side product. The overall yield of the new synthetic sequence is comparable to the previous one. Two advantages of the new procedure are: (a) no benzyl ester was formed and (b) a stereoisomeric mixture of syn- and anti-alcohols at the beginning of the synthetic sequence could be separated and the rest of the synthesis could be carried out with the main syn-stereoisomer instead of the corresponding stereoisomeric mixture as it was the case in the previous process. Additionally, several functional 2,8-ethanonoradamantane derivatives have been prepared.

Tetra-porphyrin molecular tweezers: two binding sites linked via a polycyclic scaffold and rotating phenyl diimide core

The synthesis of a tetra-porphyrin molecular tweezer with two binding sites is described. The bis-porphyrin binding sites are aligned by a polycyclic scaffold and linked via a freely rotating phenyl diimide core. Synthesis was achieved using a divergent approach employing a novel coupling method for linking two polycyclic units to construct the core, with a copper(ii)-mediated phenyl boronic acid coupling found to extend to our polycyclic imide derivative. We expect this chemistry to be a powerful tool in accessing functional polycyclic supramolecular architectures in applications where north/south reactivity and/or directional interactions between modules are important. Porphyrin receptor functionalisation was undertaken last, by a four-fold ACE coupling reaction on the tetra-epoxide derivative of the core.