Jacqueline Gabard

Chirality directed self-assembly. Resolution of 2,5-diazabicyclo[2.2.2]octane-3,6-dione and crystal structures of its racemic and (−) enantiomeric forms

The chiral bicyclic bis-lactam 1 has been resolved and the crystal structures of the racemate (±)-1 and of enantiomerically pure (−)-1 have been determined. They show that the chiral nature of the substance determines the supramolecular architecture generated by hydrogen bonding self-assembly, giving an infinite zig-zag chain for the racemate and a cyclic tetramer for the enantiomer.

Practical synthesis of optically active α-hydrazino acids from α-amino acids

Abstract Simple amino acids (1) can be converted in fair to good yield into hydrazino acids (3) of like configuration by using KOCl instead of NaOCl to promote the Shestakov rearrangement of the intermediate hydantoic acids (2).

Synthesis and absolute configuration of chiral (C3) cyclotriveratrylene derivatives. Crystal structure of (M)-(–)-2,7,12-triethoxy-3,8,13-tris-[(R)-1-methoxycarbonylethoxy]-10,15-dihydro-5H-tribenzo[a,d,g]-cyclononene

The absolute configuration of chiral C3-cyclotriveratrylene derivatives has been determined unambigously as follows. First, the absolute configuration of 2-(2-ethoxy-4-hydroxymethylphenoxy)propionic acid (5b) was established as R-(+) by chemical correlations and circular dichroism measurements. Upon treatment with perchloric acid, compound (+)-(5b) leads to the title compound (–)-(3), isolated in 14% yield, m.p. 127 °C, [α]D25–16.1°(CHCl3). The crystal and molecular structure of (–)-(3) have been determined by single crystal X-ray analysis: orthorhombic, a= 23.428, b= 22.165, c= 15.145 A space group P212121, Z= 8. The M absolute configuration has been ascribed to (–)-(3), on the basis of internal comparison with groups –CH(Me)CO2Me whose absolute stereochemistry is derived from that of (+)-(5b). Seven chiral C3-cyclotriveratrylene derivatives have been chemically related to (M)-(–)-(3). The absolute configurations so established are identical with those deduced independently from an exciton analysis of circular dichroism spectra.

Macroscopic expression of molecular recognition. Supramolecular liquid crystalline phases induced by association of complementary heterocyclic components

Whereas the pure compounds are non-mesogenic, equimolar mixtures of the complementary components (5)–(7) and (11) present a liquid crystalline phase that may be attributed to the formation of the mesogenic supramolecular species (12).

Recherches sur les substances mesogenes—VIII : Preparation et proprietes mesomorphes de series isometriques

Resume La synthese et les proprietes mesomorphes de diverses series de composes mesogenes isometriques sont decrites. Il se confirme que des molecules mesogenes isometriques peuvent, selon la place du noyau rigide polaire, etre nematogenes et/ou smectogenes.

Synthesis of a (D3)-bis(cyclotriveratrylenyl) macrocage by stereospecific replication of a (C3)-subunit

(D3)-Bis(cyclotriveratrylenyl)(4), has been synthesized in racemic and optically active forms by stereo-specific replication of a (C3)-subunit; the absolute configuration of (+)-(4) was assigned from that of the (C3)-precursor.

New D3 and C3h cryptophanes with ethylenic bridges: syntheses, structural assignments, and absolute configurations and circular dichroism of the D3 isomers

Abstract Two (D3/C3h) cryptophane pairs, (I/J) and (K/L), in which the two cyclotriveratrylene caps are linked by three trans (I/J) or cis (K/L) OCH2CHCHCH2O bridges have been synthesised, and their structures established by mass spectrometry, NMR, optical activity and circular dichroism data. The D3 cryptophanes I and K have been obtained in racemic and resolved forms, and their absolute configurations have been determined by chemical correlation with the known P-(-)-cyclotriguaiacylene. The circular dichroism spectra of I and K could be satisfactorily analyzed in the light of the exciton model, extended to the coupling of six equivalent chomophores in a D3 array.

(C3)-Tris-(O-allyl)-cyclotriguaiacylene, a key intermediate in cyclotriveratrylene chemistry. Short and efficient synthesis of cyclotriguaiacylene

Straightforward access to (C3)-functionalized derivatives of cyclotriveratrylene can be attained via the readily accessible intermediate (C3)-tris-(O-allyl)-cyclotriguaiacylene.