Chiral Dendrimers

Seebàch, Dieter; Rheiner, P. Beat; Greiveldinger, Guy; Butz, Thomas; Sellner, Holger

doi:10.1007/3-540-69779-9_4

Cited by 117 publications

(58 citation statements)

References 77 publications

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“…The dendrimer was prepared by P. M. as part of a study on chiral dendritically modified catalysts within the group of Prof. D. Seebach [42] [43]. With the chiral dendritic compound presented in this study, (S,S)-1,4-bis(dimethylamino)-2,3-dimethoxybutane (DDB) was tested as a core moiety for dendritic amine catalysts.…”

Section: Experimental Partmentioning

confidence: 99%

Hourglass‐Shaped Dendrimers on Surfaces: A Comparison of Different Scanning‐Tunneling‐Microscopy Approaches

Widmer

Hubler

Stöhr

et al. 2002

Helvetica Chimica Acta

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Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday Large molecules adsorbed on surfaces can be analyzed by scanning tunneling microscopy (STM) under various environmental conditions: on a dry surface in air or vacuum, and at the solid-liquid interface. However, can measurements under dissimilar conditions be compared, e. g., when sample A was studied at the solid-liquid interface and sample B in a dry environment? Only rarely can the same substance be examined with more than one approach, since completely different set-up and preparations are necessary. Furthermore, few substances are suitable for several methods of sample preparation and characterization. We have chosen a large, flexible, nonplanar molecule, namely an alkoxy-substituted second-generation dendritic compound with a chiral core unit, which is peculiar for its −hourglass× conformation. The assembly properties have been explored by STM both in solution-cast self-organized monolayers (SOMs) and multilayer films, as well as at the solid-liquid interface. The complexity and limits of the three approaches applied to our hourglass-shaped dendritic compound are discussed. Depending on the approach and environmental conditions, several quality levels of image resolution could be achieved; measurements carried out at low temperatures led to highest resolution on the aromatic parts of the molecule. A comparison of equally sized images obtained under these varying conditions reveals not only different packing arrangements, but also spots of unlike shape. Therefore, when the approach, preparation, and/or environmental conditions are not the same, STM measurements of different compounds have to be compared with greatest care.

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Section: Experimental Partmentioning

confidence: 99%

Hourglass‐Shaped Dendrimers on Surfaces: A Comparison of Different Scanning‐Tunneling‐Microscopy Approaches

Widmer

Hubler

Stöhr

et al. 2002

Helvetica Chimica Acta

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“…In the case of the Zn II complex 8-ZnCl 2 , both Dcis-a(S,S,l) and Lcis-a(R,R,l) stereoisomers were found in the unit cell. For the Cu secondary interactions in chiral dendrimers, [24][25][26][27] conformational order was found to be lacking. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Recently, we introduced the concept of chiral depsipeptide dendrimers as peptide or protein mimetics.…”

Section: Introductionmentioning

confidence: 99%

Metal‐Induced Chiral Folding of Depsipeptide Dendrimers

Buschhaus¹,

Hampel²,

Hirsch³

2005

Chemistry A European J

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The synthesis and metal complexation of chiral depsipeptide dendrimers 3 and 7 containing an ethylenediaminetetraacetic acid (EDTA) ester‐derived core is reported. The EDTA ester cavity of these dendrimers selectively complexes Zn2+ and Cu2+ ions leading to diastereoselective folding. To elucidate the coordination motif in the resulting “foldamers” of 3‐ZnCl2, 7‐ZnCl2, 3‐CuCl2, and 7‐CuCl2, the coordination behavior of the tetramethyl ester of EDTA (8) has been investigated as a model case. The corresponding complexes 8‐ZnCl2 and 8‐CuCl2 have been structurally characterized by 1H NMR spectroscopy and X‐ray analysis. The complexes involve the inherently chiral octahedral cis‐α coordination motif, in which 8 serves as a tetradentate ligand. In the case of the ZnII complex 8‐ZnCl2, both Δcis‐α(S,S,λ) and Λcis‐α(R,R,λ) stereoisomers were found in the unit cell. For the CuII complex 8‐CuCl2, only one stereoisomer, namely Δcis‐α(S,S,λ) was found in the crystal under investigation. 1H NMR spectroscopy has shown that the same coordination motif is diastereoselectively formed in the chiral Zn2+ dendrimers 3‐ZnCl2 and 7‐ZnCl2. Likewise, the calculated CD spectrum of the Δcis‐α(S,S,λ) stereoisomer of the model complex 8‐CuCl2 shows good agreement with the experimental spectrum of the CuII dendrimers 3‐CuCl2 and 7‐CuCl2, allowing assignment of the absolute configurations of the preferred foldamers as Λcis‐α(R,R,λ) for 3‐CuCl2 and Δcis‐α(S,S,λ) for 7‐CuCl2. This work represents the first example of metal‐complexation‐mediated diastereoselective folding of chiral dendrimers with known absolute configuration.

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“…(50 ml of each). Drying (Na 2 CO 3 ), evaporation to dryness, and CC (SiO 2 ; hexane/AcOEt 8 : 2) provided 10 (0.132 g, 64% (12). To 8 (0.297 g, 0.42 mmol) in dry CH 2 Cl 2 (10 ml), oxalyl chloride (0.6 g, 4.72 mmol) was added by syringe, and the mixture was stirred for 12 h. After evaporation in vacuo, the crude acyl halide was dried in high vacuum (10 À1 Torr/r.t., 4 h) and dissolved in THF (5 ml).…”

Section: Experimental Partmentioning

confidence: 99%

“…This study describes the first examples of chiral molecular recognition within a dendritic superstructure (for a review on chiral dendrimers, see [12]). The three novel dendroclefts form 1 : 1 host-guest complexes with monosaccharides (for general discussions on the larger number of molecular receptors synthesized for carbohydrate recognition, see [13]), and we show that the enantio-and diastereoselectivity of the recognition events is strongly dependent on the dendritic generation.…”

mentioning

confidence: 99%