Size effects in the alkali metal ion-templated formation of oligo(ethylene glycol)-containing [2]catenanes

Lee, Yong-Jay; Ho, Tsung-Hsien; Lai, Chien‐Chen; Chiu, Sheng‐Hsien

doi:10.1039/c5ob01956g

Cited by 19 publications

(26 citation statements)

References 38 publications

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“…Thus, we speculated that the thermodynamic macrocycle-metal binding data obtained from ITC experiments might be correlated to the kinetic phenomena in the ion-templated MCO. 33,37,39…”

Section: Introductionmentioning

confidence: 99%

Evidence for Ion-Templation During Macrocyclooligomerization of Depsipeptides

Batiste

Johnston

2018

J. Am. Chem. Soc.

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The ion-mediated Mitsunobu macrocyclooligomerization (M-MCO) reaction of hydroxy acid depsipeptides provides small collections of cyclic depsipeptides with good mass recovery. The approach can produce good yields of a single macrocycle or provide rapid access to multiple oligomeric macrocycles in good overall yield. While Lewis acidic alkali metal salts are known to play a role in the outcome of MCO reactions, it is unclear whether their effect is due to an organizational (e.g., templating) mechanism. Isothermal titration calorimetry (ITC) was used to study macrocycle-metal ion binding interactions, and this report correlates these thermodynamic measurements to the (kinetically determined) size distributions of depsipeptides formed during a Mitsunobu-based macrocyclooligomerization (MCO). Key trends have been identified in quantitative metal ion-cyclic depsipeptide binding affinity ( K), enthalpy of binding (Δ H), and stoichiometry of complexation across discrete series of macrocycles, and they provide the first analytical platform to rationally select a metal-ion template for a targeted size regime of cyclic oligomeric depsipeptides.

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“…Thus, we speculated that the thermodynamic macrocycle-metal binding data obtained from ITC experiments might be correlated to the kinetic phenomena in the ion-templated MCO. 33,37,39…”

Section: Introductionmentioning

confidence: 99%

Evidence for Ion-Templation During Macrocyclooligomerization of Depsipeptides

Batiste

Johnston

2018

J. Am. Chem. Soc.

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“…As displayed in Figure a, the 1 H NMR spectrum of an equilibrated (323 K, 160 h) equimolar (20 mM) mixture of the diamine 1 , the dialdehyde 2 , the DEG-containing macrocycle 6 , and NaTFPB {TFPB = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate} (Scheme ) featured several significantly upfield shifted signals for the protons of the DEG unit of the [2]catenanes. Considering our previous experience , and 2D COSY and NOESY spectra (see the Supporting Information), we identified the signals at δ 2.61 and 2.99 as representing the protons of the DEG unit of the interlocked imino macrocyclic component 3 in the homo[2]catenane [ 4· Na] + and the hetero[2]catenane [ 13· Na] + , respectively, and the signals at δ 2.46 and 2.91 as representing the DEG unit of the macrocyclic component 6 in [ 13· Na] + . Nevertheless, an intense signal at δ 3.52 in the equilibrated mixture, representing the resonances of the protons of the Na + -complexed DEG unit of the macrocycle 6 , suggested that the formation of the [2]catenane [ 13· Na] + was not efficient under the reaction conditions.…”

Section: Results and Discussionmentioning

confidence: 99%

“…On the basis of integration of these signals, the molar ratio of the hetero[2]catenane [ 13· Na] + , the homo[2]catenane [ 4· Na] + , and the macrocycle [ 6· Na] + was 1.7:1.0:3.2. Using NaBH 4 to reduce the mixture formed on a larger scale, but under similar conditions, followed by Eschweiler–Clarke methylation, we isolated the hetero[2]catenane 14 and the homo[2]catenane 15 in yields of 14% and 7%, respectively (the recovery yield of 6 was 59%). Thus, clipping the DEG-containing imino macrocycle 3 onto the DEG-containing macrocycle 6 in the presence of templating Na + ions was not particularly selective or efficient.…”

Section: Results and Discussionmentioning

confidence: 99%

“…A similar strategy of incorporating one ligand into the structure of a macrocycle does not appear to proceed efficiently when using the Na + /oligo(ethylene glycol) (OEG) recognition system. The clipping of the di(ethylene glycol) (DEG)-containing imino macrocycle 3 , formed from the diamine 1 and the dialdehyde 2 (Figure a), onto OEG-incorporated macrocycles has afforded hetero[2]catenanes with only moderate yields (21–28%, Figure b), presumably because of the inability to inhibit the formation of the competing imino homo[2]catenane [ 4· Na] + , as evidenced by the isolation of the homo[2]catenanes 5 after NaBH 4 -mediated reduction. We suspected that this low efficiency was largely due to the poorly directional binding of OEG chains, leading to both internal threading and external binding (Figure c), making the principle of maximum site occupancy less practical in avoiding the formation of competing homo[2]catenanes.…”

Section: Introductionmentioning

confidence: 99%

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Complementarity of 2,6-Dimethanolpyridine and Di(ethylene glycol) in the Complexation of Na⁺ Ions: Attaching Multiple Copies of [2]Catenane Branches to Isophthalaldehyde-Containing Cores

Chen

et al. 2021

J. Org. Chem.

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In this study we found that 2,6-dimethanolpyridine displays good complementarity toward di(ethylene glycol) for the complexation of Na+ ions, allowing us to use this recognition system for the efficient synthesis of hetero[2]catenanes; indeed, it allowed us to attach multiple copies of [2]catenanes to branched systems presenting multiple isophthalaldehyde units. When we attempted to form a catenane from a preformed macrocycle featuring only a single di(ethylene glycol) unit, reacting it with a di(ethylene glycol) derivative presenting two amino termini, isophthalaldehyde, and templating Na+ ions [i.e., with the aim of using di(ethylene glycol)·Na+·di(ethylene glycol) recognition to template the formation of the interlocked imino macrocycle], the yields of the hetero[2]catenane and homo[2]catenane, comprising two imino macrocyclic units, were both poor (14% and 7%, respectively). In contrast, when one or two 2,6-dimethanolpyridine units were present in the preformed macrocycles, their reactions with the same diamine, dialdehyde, and Na+ ions provided the hetero[2]catenanes with high selectivity and efficiency (44% and 64% yields, respectively), with minimal formation of the competing homo[2]catenane. The high complementary of the 2,6-dimethanolpyridine·Na+ ·di(ethylene glycol) ligand pair allowed us to synthesize [2]catenane dimers and trimers directly from corresponding isophthalaldehyde-presenting cores, with yields, after subsequent reduction and methylation, of 42% and 31%, respectively.

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“…We prepared the [2]rotaxane 1 , comprising the macrocyclic component 2 and the dumbbell‐shaped component 3 (Scheme ), through alkali metal ion templated clipping of an imino macrocycle and subsequent reduction . 2D COSY and NOESY experiments allowed us to identify most of the signals in the 1 H NMR spectra of the [2]rotaxane 1 in [D 8 ]toluene at 298 K (Figure , see the Supporting Information for the full signal assignments).…”

Section: Figurementioning

confidence: 99%