Factors Affecting Conformation of ( R,R )-Tartaric Acid Ester, Amide and Nitrile Derivatives. X-Ray Diffraction, Circular Dichroism, Nuclear Magnetic Resonance and Ab Initio Studies

Gawroński, Jacek; Gawrońska, K.; Skowronek, Paweł; Rychłewska, Urszula; Warżajtis, Beata; Rychlewski, Jacek; Hoffmann, Marcin; Szarecka, Agnieszka

doi:10.1016/s0040-4020(97)00271-8

Cited by 57 publications

(67 citation statements)

References 59 publications

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“…The mono-deprotected tartaric acid derivative 8 was prepared according to a literature procedure. [17] Formation of the coupling product 9 was accomplished by reaction of 7 with 8 in the presence of N,N'-dicyclohexylcarbodiimide (DCC) at 0 8C in CH 2 Cl 2 (Scheme 2). The removal of the benzylic protecting groups by catalytic hydrogenation afforded the acid 10.…”

Section: Resultsmentioning

confidence: 99%

Depsipeptide Dendrimers

2000

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The convergent synthesis of a new class of chiral dendrimers is described. Owing to their structural resemblance to depsipeptides they are called depsipeptide dendrimers. The ex-chiral pool synthesis starts from (R,R)-, (S,S)-, and meso-tartaric acid as branching units and dipeptides or tripeptides consisting of glycine, (L)-alanine, and (L)-leucine as chiral-spacer building blocks. The key intermediates for the convergent assembly of such depsipeptide dendrimers are the peptide-tartaric acid conjugates 13a,b, 19a,b, 25, and 27, which contain either an unprotected C terminus of the peptide chain (13 a,b, 25) or two unprotected hydroxy groups within the tartaric acid termini. Dendra up to the third-generation, by using different combinations of stereoisomeric building blocks, were synthesized and completely characterized. Since this construction principle of chiral depsipeptide dendrimers allows for a wide variation of the length, the primary structure of the peptide spacer, and the configuration of both the amino acid and the tartaric acid moieties, access to new combinatorial libraries is conceptually provided.

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Section: Resultsmentioning

confidence: 99%

Depsipeptide Dendrimers

2000

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“…2). The anticonformation (T) is the most commonly encountered in solution and in the solid state 7 but the interaction with a dicationic amphiphile may affect this predominant conformation. On the other hand, when tartrate molecules are confined in a helical structure, their molecular chirality will be interconnected to the supramolecular chirality of the helical ribbons.…”

Section: Introductionmentioning

confidence: 99%

Molecular and supramolecular chirality in gemini‐tartrate amphiphiles studied by electronic and vibrational circular dichroisms

et al. 2009

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This contribution presents an application of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) to study the molecular and supramolecular chirality in assemblies of gemini-tartrate amphiphiles. Nonchiral dicationic n-2-n amphiphiles (n 5 14-20) can self-organize into right-or left-handed structures upon interacting with chiral tartrate counterions. Micellar solutions can also be obtained for shorter alkyl chains (n 5 12). First, the conformation of tartrate counterions has been investigated in various environments (micellar solutions and chiral ribbons). ECD and VCD spectra recorded in micellar solutions are independent from the solvent and from the nature of the cations (sodium, cetyl-trimethylammonium, or dimeric surfactant 12-2-12) used and are representative of the anticonformation of the tartrate dianions. On the other hand, drastic changes in the ECD and VCD spectra have been observed in multilayered chiral assemblies of 16-2-16 tartrate. These strong spectral modifications are associated with the chiral arrangement of the tartrate molecules at the surface of the bilayers. Moreover, chirality transfer from counterions to achiral amphiphiles has been clearly evidenced by VCD since circular dichroism has been observed on vibrations related to alkyl chains and gemini headgroups. Finally, ECD and VCD experiments were performed varying the enantiomeric excess of the tartrate. The ECD and VCD intensities do not vary linearly with the enantiomeric excess of the anion and different behaviors have been observed from the two spectroscopic methods: ECD intensities are correlated to the pitch of the ribbons, whereas the VCD intensities are correlated to the dimension of the chiral ribbons.

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“…The observed asymmetry of the molecule is reflected in the crystal packing as the two carbonyl groups have totally different surroundings (vide infra). Our studies on (R,R)-tartaric acid derivatives seem to indicate that conformational freedom about the C *--C bond is characteristic for an ester group and is not observed within a α-hydroxycarboxyl or amide moiety [12,18,20]. For example in the crystal structure of the methyl ester of (R,R)-tartaric acid monoamide, methyl ester groups from two independent molecules adopt alternate orientations, i.e.…”

Section: X-ray Crystallographymentioning

confidence: 75%

“…they are rotated by 180° around the C-C * bond [20]. The α-hydroxyester moiety exhibits a planar conformation in all tartaric acid esters studied so far by X-ray diffraction methods [1,12,18,20]. Such tendency also prevails in isolated molecules as indicated by ab initio methods (vide infra).…”

Section: X-ray Crystallographymentioning

confidence: 85%

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(R,R)-Tartaric Acid Dimethyl Diester from X-Ray and Ab Initio Studies: Factors Influencing Its Conformation and Packing

et al. 1997

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Abstract:The conformation of dimethyl (R,R)-tartrate has been analyzed on the basis of the single crystal X-ray diffraction method as well as by ab-initio quantum chemical studies. The results showed that the extended T conformation containing two planar hydroxyester moieties predominates in both ab-initio and X-ray studies. The lowest energy conformer in ab-initio calculations has C 2 symmetry and hydrogen bonds between a hydroxyl group and the nearest carbonyl oxygen. The second in energetical sequence, with an energy difference of only 1.2 kcal/mol, is the asymmetrical conformer, which differs from the lowest energy form by the rotation of one of the ester groups by 180°. Intramolecular OH ... O hydrogen bonds observed in this rotamer again involve only proximal functional groups. This conformer is present in the crystal structure of the studied compound, although its conformation in the solid state is no longer stabilized by intramolecular hydrogen bonds of the type mentioned above. In the crystal, hydroxyl groups are mostly involved in intermolecular hydrogen bonds and form only a weak intramolecular hydrogen bond with each other. The planar arrangement of the α− hydroxyester moieties combined with the extended conformation of the carbon chain seems to be stabilized by the intramolecular hydrogen bonds between neighboring functional groups and by the long range dipole-dipole interactions between two pairs of CO and (β)C-H bonds.

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Factors Affecting Conformation of ( R,R )-Tartaric Acid Ester, Amide and Nitrile Derivatives. X-Ray Diffraction, Circular Dichroism, Nuclear Magnetic Resonance and Ab Initio Studies

Cited by 57 publications

References 59 publications

Depsipeptide Dendrimers

Depsipeptide Dendrimers

Molecular and supramolecular chirality in gemini‐tartrate amphiphiles studied by electronic and vibrational circular dichroisms

(R,R)-Tartaric Acid Dimethyl Diester from X-Ray and Ab Initio Studies: Factors Influencing Its Conformation and Packing

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