Helicenes. Resolution on chiral charge-transfer complexing agents using high performance liquid chromatography

Abstract

11 Optically pure octa-, nona-, deca-, undeca-, and trideca-helicenes have recently been synthesised starting from optically pure la Rs is the resolution function, the total measure of component peak separation a t their apexes and baselines; see L. R. Snyder hexahelicene-2-carboxylic acid (V. Libert, and R. H. Martin, personal communication).

One hundred years of helicene chemistry. Part 2: stereoselective syntheses and chiral separations of carbohelicenes

“…As for [5]helicene, the (+)-enantiomer eluted first on (À)-TABA (2-(2,4,5,7-tetranitro-9-fluorenylidenaminooxy)butyric acid) and a preliminary work was published by Gil-Av and co-workers in 1976. 141 The separation of helicene enantiomers ([5]-to [14]helicene) has been fully investigated by the same authors with (À)-TAPA linked to amino silica gel or coated (25%) on silica gel with cyclohexane-methylene chloride as a mobile phase. 142 Three other TAPA derivatives have also been studied under similar conditions by changing a substituent at the stereogenic center from a methyl to an ethyl group (TABA), to an isopropyl (TAIVA) or to a butyl group (TAHA).…”

Reciprocal principle of molecular recognition in supramolecular chromatography—highly selective analytical separation of cyclodextrin congeners on a silica-bonded [60]fullerene stationary phase

“…Hitherto, only chemically modified chiral [60]fullerene-and [70]fullerene-adducts (mono-, bis-, tris-, hexakis-) have been resolved into their enantiomers by LC [33][34][35][36] both on a Whelk-O1 selector 6,7 and a (+)-TAPA-selector. 2 Pirkle and Hoover pointed out that molecular recognition usually rests on complementary functionalities which permits their interaction. 3 The present reciprocal supramolecular system involves an abiotic aromatic cluster and a biogenic cycloamylose and their mutual molecular recognition ability is most likely governed by shape selectivity.…”

“…1 In chromatographic partitioning systems, the selector can be present as a stationary phase or as an additive to the liquid phase. 1 Following the enantioseparation of helicenes on the optically active charge-transfer agent 2-(2,4,5,7-tetranitro-9fluorenylideneamino-oxy)propionic acid (TAPA), 2 Mikesš peculated that the function of the selector and the selectand could be reversed, i.e., helicenes used as resolving agents. 1 Thus, in a reciprocal fashion, if the selectands A1 and A2 are chromatographically separated on the selector B1 (or B2), also the selectands B1 and B2 should be separated on the selector A1 (or A2) whereby the respective pairs A1/A2 and B1/B2 refer to isomers (e.g., stereoisomers) or to members of homologous series of compounds (Fig.…”

The Reciprocal Principle of Selectand-Selector-Systems in Supramolecular Chromatography †

“…Following the enantioseparation of [5]–[14]helicenes on the optically active charge-transfer agent R -2-(2,4,5,7-tetranitro-9-fluorenylideneamino-oxy)propionic acid (TAPA, Figure 1) or its 2-butyric acid homologue (TABA) [9,10,11], Mikeš speculated that the function of the selector and the selectand could be reversed, i.e., optically active helicenes could be used as resolving agents for racemic compounds [4]. Thus, in a reciprocal fashion, if the selectands A1 and A2 are chromatographically separated on the selector B1 (or B2), the selectands B1 and B2 are separated on the selector A1 (or A2) as well, whereby the respective pairs A1/A2 and B1/B2 refer to isomers (e.g., stereoisomers) or belong to members of homologous series of compounds (Figure 2).…”