Structural and Spatial Considerations in theN,N′-Diacyl- and Bis(alkoxycarbonyl)bispidinone Series

Abstract

Diamidic and dicarbamic bispidinones show trans-cis isomerism, the relative population in solution of the cis form increasing with solvent polarity. The mutual proximity of the two amide functions in 4a has no impact on the barrier to isomerization. The system represents a peculiar case of planar chirality posing a challenge to its specification.

Bispidine as a β-strand nucleator: from a β-arch to self-assembled cages and vesicles

“…20 In CDCl3, the ratio of anti to syn was 3:1, while DMSO favored the structure with high dipole moment, the syn conformer. 24,25 ROESY spectrum confirmed the presence of syn and anticonformers in F3 (Fig. 3a, b).…”

Bispidine Platform as a Tool for Studying Amide Configuration Stability

“…. C separations found in published papers on bispidine bis-amides range from 3.041 [14] to 4.696 Å [13] (here, we compare only the C . .…”

“…These differences the level of rigidity of the bispidine core: while the macrocyclic nature of 3 dicta spatial proximity of the carbonyl groups in the 10-membered ring, the acyclic mole could adopt a more relaxed conformation of the bicyclic core. The values of C…C s tions found in published papers on bispidine bis-amides range from 3.041 [14] to 4 [13] (here, we compare only the C…C distance since O…O separation obviously for the syn-and anti-forms). These findings clearly demonstrate that, in contrast widely known conformational rigidity of the bispidine bicycle in the double-chair c mation, the subtle structural factors could have a pronounced impact on the spatial ture of the molecules, even in the case when a system contains conventionally plan conformationally stable amide moieties.…”

“…The equilibrium constant for anti/syn interconversion strongly depends on the nature of the solvent: in more polar solvents, the syn-form predominates since it possesses a higher dipole moment compared to the anti-form [12][13][14]. It should be noted here that the presence of a metal ion in a solution could strongly affect the resulting syn/anti ratio towards the prevalence of the syn-form due to chelation of a metal center by two oxygen atoms, which are in close proximity in the syn-form [12,15].…”

Conformational Study of N,N′-Diacyl Bispidines and Dioxo Bis-bispidines: Planar Chirality and Molecular Switching

“…5 In 2008, planar chirality was observed in bispidinones 2 (R = COMe, R′ = Ph) by Albeck and co-workers through NMR studies. 6 As part of our research on functionalized bisbispidines, 7−9 it was found that bispidines 1 (R = COCH 2 X, R′ = H) exhibit chirality in the absence of chiral centers. Analysis of the molecular structure indicates planar chirality, which has been confirmed by X-ray diffraction studies.…”