Synthesis and chiroptical properties of cylindrical macrocycles comprising two calix[3]aramide moieties

Abstract

Novel chiral macrocyclic aromatic amides of medium molecular weight were synthesized by the one-step amide coupling of a bis(alkylamino)terphenyl diacid as monomer.

Cylindrical macrocyclic compounds synthesized by connecting two bowl-shaped calix[3]aramide moieties: structures and chiroptical properties

“…Calix[3]aramide 2 was synthesized from 3-nitrobenzoic acid using a known procedure. 6 A Sonogashira-Hagiwara cross coupling reaction of calix[3]aramide 2 with trimethylsilylacetylene in the presence of PdCl 2 (dppf) and copper(I) iodide gave calix[3]aramide 3 in 96% yield. By deprotection of the silyl group, calix[3]aramide 4 was obtained in 90% yield.…”

“…2) suggested that the product was a mixture of diastereomers with a xed calix [3] aramide structure because the aromatic protons were observed symmetrically, as in the case of the dimeric products linked by a phenylene group that we previously reported. 6 The yield of dimeric products of 1 from calix[3]aramide 4 was 38%. A diastereomeric mixture of 1 was successfully separated by chiral HPLC using a ChiralPAK IA column, giving three components in a 1 : 2 : 1 ratio in the order of retention time (Fig.…”

“…These stereoisomers were generated due to different combinations of amide bond direction in the calix [3]aramide moieties at each end of the molecule, as in the case of the phenylene-linked derivatives. 6 That is, the stereoisomers that were ECD active contained a homochiral combination of the calix[3]aramide moieties [1-chiral: 1-(PP) and 1-(MM)], while the stereoisomer that was ECD inactive contained heterochiral combination [1-meso: 1-(PM)]. The ratio of 1-chiral to 1-meso was 1 : 1, indicating that there was no energy difference between their reaction intermediates during the coupling reaction.…”

“…12 Subsequently, we synthesized cylindrical macrocyclic aromatic amides of medium molecular weight by a one-step cyclization reaction of a compound that had two sets of both alkylamino and carboxy groups as a monomer. 5,6 In the present study, we successfully synthesized macrocyclic aromatic amides with three butadiynylene groups by connecting two equivalent meta-calix [3]aramides with three ethynyl groups using a Glaser coupling reaction 13 (Fig. 1).…”

“…3 These medium-molecularweight compounds with macrocyclic structures, 1-4 which consist of only covalent bonds, are robust and resistant to decomposition by solvent or high temperature conditions. Generally, synthetic strategies for such compounds, especially those with highly symmetric structures, have been a cyclized reaction of monomer 1c, 5,6 or a condensation of several partial structures. 2a,2c,3 We focused on the condensation of two bowlshaped compounds 1b,2b,7 and attempted to synthesize chiral molecules with medium molecular weight using this synthetic strategy.…”