オリゴピロール誘導体のらせん構造制御

Abstract

Unique cyclooligopyrroles with figure of 8 conformation were prepared from useful pyrrole intermediates such as bis(azafulvene)s and 2-borylpyrrole. [32]Octaphyrin-(1.0.1.0.1.0.1.0) 1 with 32π-cycloconjugation exists in a P,P- and a M,M-helical form, which are rapidly interchanged by the stretching-compressing mechanism. Cyclooctapyrrole 1 was successfully applied to a chirality sensor for determining absolute configuration of chiral carboxylic acids taking advantage of the unique chiroptical property. Calix[8]phyrin 2 having interrupted π-conjugation also undergoes rapid conformational change in solution, but its dinuclear CuII complex 2Cu2 was resolved into enantiomers by HPLC on chiral phase. Metal insertion into 2 in the presence of (R)-(+)-1-(phenyl)ethylamine caused helix sense bias to the P,P-helicity. Cyclotetrapyrroletetrapyridine 3 composed of eight heterocycles also takes helical conformation and provides dual monoanionic tridentate coordination environment. Its dinuclear CoII complexes 3Co2L2 with an amino acid anion (L−) at each metal site could be isolated to show full helix sense bias in the case of Thr, Phe, Tyr, and Trp. An open chain oligopyrrole was also studied to generate helix sense bias. Dinuclear PdII complex 4Pd2 of hexapyrrole-α,ω-dialdehyde was reacted with (R)-(−)-1-cyclohexylethylamine to give the corresponding α,ω-diimines with 85% diastereoselectivity in favor of the P helical conformation, the chiroptical property of which could be tuned by redox.