Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis

Greschner, Wilko; Neumann, Beate; Stammler, Hans‐Georg; Gröger, Harald; Kuck, Dietmar

doi:10.1002/anie.201506906

Cited by 26 publications

(19 citation statements)

References 51 publications

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“…Hydrolysis under basic conditions gave the corresponding benzyl alcohol (-)-(P)-7 in almost quantitative yield and subsequent Swern oxidation furnished the respective TBTQ-based benzaldehyde (-)-(P)-6 in 94 % yield. Both compounds had already been described in our previous report [20] and were obtained in excellent optical purity (>99 % ee) here as well.…”

Section: Chirality-assisted Synthesis Of the Syn-bi-concave 14-dioxisupporting

confidence: 58%

“…However, owing to the use of the enantiomerically pure precursor (M)-10 for the Ullmann-type cyclocondensation, there is no doubt that the syn-diastereomer, 5, was formed exclusively. [12,[20][21][22] Irrespective of the enforced syn-stereochemistry of 5 and in view of its model character as a subunit of a potential (TBTQ) 8 cube and similar oligomers, we aimed at the elucidation of structural details by X-ray diffraction. After many futile attempts, we succeeded to grow single crystals of 5 suitable for X-ray structural analysis by very slow evaporation of the solvent from solutions in dichloromethane/methanol, 20:1 (v/v).…”

Section: Chirality-assisted Synthesis Of the Syn-bi-concave 14-dioximentioning

confidence: 99%

“…[13][14][15][16] Among the latter, various enantiomerically pure TBTQ derivatives have been reported and optical resolution was achieved by use of chiral auxiliaries, [11a,17,18] by chiral chromatography, [19] and by enzyme-catalyzedenantioselectivesynthesis. [20] Inseveralcases,enantiomerically pure TBTQ derivatives were shown to form cubic assemblies [10a,12] or molecular squares [19a] in analogy to the recently proposed concept of chirality-assisted synthesis. [21,22] Therefore, the facile access to enantiomerically pure TBTQ synthons and their utilization for the construction of novel, threedimensional molecular assemblies and networks represent a challenging field in organic chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…We chose TBTQ-2-carbaldehyde 6 (Scheme 2) as a starting point to prepare the corresponding TBTQ-based benzyl acetate rac-8 as a racemic substrate for the enzymatic resolution on a multi-gram scale. [20] The optically pure enantiomer (P)-8 was then converted into the corresponding ortho-iodophenol (M)-10 and subsequent chirality-assisted Ullmann-type condensation of this enantiomer gave the bi-concave dioxine-fused TBTQ "dimer" 5. In analogy to phenazine-merged dimers of type 4, dibenzodioxine 5 represents an achiral compound bearing the bowls of the two TBTQ units in mutual syn-configuration, thus suitably oriented toward the interior of a hypothetical (TBTQ) 8 cube.…”

Section: Introductionmentioning

confidence: 99%

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Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

et al. 2018

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The stereoselective synthesis of enantiomerically pure single‐wing‐functionalized tribenzotriquinacenes using the enzyme CAL‐B was successfully extended towards operating on a multi‐gram scale. Based on the (P)‐tribenzotriquinacene‐2‐carbaldehyde (P)‐6 obtained in >99 % ee, the hitherto unknown (P)‐2‐hydroxy‐ and (M)‐2‐hydroxy‐3‐iodo‐TBTQ derivatives (P)‐9 and (M)‐10 were prepared in optically pure form. The bowl‐shaped ortho‐iodophenol (M)‐10 was subjected to a twofold crosswise Ullmann‐type condensation to give, albeit in low yield (10 %), the 1,4‐dioxine 5, in which two TBTQ bowls are fused exclusively in a syn‐bi‐concave orientation, thus demonstrating a new example for a chirality‐assisted synthesis. The corresponding Ullmann condensation of the racemic TBTQ‐ortho‐iodophenol rac‐10 furnished the respective anti‐bis‐TBTQ‐dioxine 11 as the major diastereomer together with the syn‐isomer 5 in the same total yield and in a 11/5 ratio of at least 4. The two diastereomeric bis‐TBTQ‐dioxines show minor but significant differences in most of the characteristic 1H‐NMR chemical shifts. The solid‐state structure of the syn‐dimer 5, determined by X‐ray diffraction, was found to consist of pairs of host–guest complexes, [5·CH2Cl2]2, with pronounced face‐to‐face orientation of the bi‐concave host molecules.

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Section: Chirality-assisted Synthesis Of the Syn-bi-concave 14-dioxisupporting

confidence: 58%

Section: Chirality-assisted Synthesis Of the Syn-bi-concave 14-dioximentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

et al. 2018

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“…[1] However,the number of enantiopure C 3 -symmetric molecules synthesized to date is severely limited [2][3][4][5][6] compared with that of C 2 -symmetric molecules,p robably due to the scarcity of appropriate synthetic approaches,a nd thus chemistry based upon C 3 -symmetric molecules remains underdeveloped. [1] However,the number of enantiopure C 3 -symmetric molecules synthesized to date is severely limited [2][3][4][5][6] compared with that of C 2 -symmetric molecules,p robably due to the scarcity of appropriate synthetic approaches,a nd thus chemistry based upon C 3 -symmetric molecules remains underdeveloped.…”

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confidence: 99%

Synthesis of Enantiopure C₃‐Symmetric Triangular Molecules

et al. 2017

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An asymmetric synthesis of C -symmetric triangular macrocycles is reported. 1-Methylsulfonyl-4-(4-vinylphenyl)-1,2,3-triazole undergoes a rhodium(II)-catalyzed cyclotrimerization to establish an enantiopure C -symmetric triangular macrocycle motif. This method can be applied to the synthesis of an enantiopure hydrocarbon, which owes its chirality to asymmetric distribution of H/D atoms on the benzene rings.

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Chirality‐Assisted Synthesis of a Very Large Octameric Hydrogen‐Bonded Capsule

2016

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The strategy of chirality-assisted synthesis, which makes use of enantiomerically pure building blocks that are designed to associate in a single geometric orientation, was applied to synthesize an octameric hydrogen-bonded capsule with a cavity volume of 2300 3 . This cube-shaped capsule forms even host-guest complexes with tetraalkylammonium ions, and accommodates the large tetrahexadecylammonium cation in its cavity. The use of an enantiopure building block was shown to be highly beneficial for capsule formation, whereas its racemate also generates a large amount of illdefined aggregates in solution and crystallizes as a hydrogenbonded network.The synthesis of artificial viral capsids self-assembled from small molecules has attracted considerable interest since the first molecular containers were reported by the groups of Cram [1] and Collet [2] in the mid-1980s. [3] Since then, the size of covalent organic [4] and metal-organic [5] cages has continuously increased, with the largest yet reported reaching a diameter of about 8 nm while partially surrounding an open cavity volume of roughly 160 000 3 . [6] In contrast, the size of closed-shell molecular capsules that spontaneously self-assemble in solution through noncovalent interactions has stagnated since hexameric resorcinarene-and pyrogallolarene-derived capsules were discovered in the late 1990s. [7] Such capsules completely enclose the space defined by their cavity, but with cavity volumes only reaching about 1400 3 they are dwarfed by even the smallest known viruses. As such, the encapsulation of large molecules (e.g., proteins and DNA fragments) by noncovalent capsules remains a long-term objective. [8] One major difficulty in the synthesis of large noncovalently bound capsules arises from the relatively poor directionality of noncovalent interactions which can result in the formation of networks instead of discrete nanosized objects. [9] In this regard, a simple way to reduce the likelihood of network formation is to design small molecules that form dimeric capsules through multiple interactions, and it is therefore not surprising that dimeric capsules [3f, 10] far outnumber tetrameric, [11] pentameric, [12] hexameric, [7a,b, 13] and higher-order capsules.[14] However, a major drawback of this approach is that the size of the molecular units required for the construction of a dimeric capsule increases at the same rate as the targeted capsule itself. From a synthetic point of view, it is far more desirable to use several small components instead of two large ones. The strategy of chirality-assisted synthesis may help solve this problem as the use of enantiopure, inherently chiral building blocks should work against the formation of polymeric materials.[15] Herein we show that this strategy can be exploited to rationally design a small molecule that predictably self-assembles into a hydrogen-bonded capsule with a very large cavity volume.Tris(isatin) 1 (Figure 1 A) was designed by combining a tribenzotriquinacene core [16] with confor...

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Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis

Cited by 26 publications

References 51 publications

Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

Synthesis of Enantiopure C₃‐Symmetric Triangular Molecules

Chirality‐Assisted Synthesis of a Very Large Octameric Hydrogen‐Bonded Capsule

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Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis

Cited by 26 publications

References 51 publications

Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

Combining Stereoselective Enzyme Catalysis with Chirality‐Assisted Synthesis in Tribenzotriquinacene Chemistry

Synthesis of Enantiopure C3‐Symmetric Triangular Molecules

Chirality‐Assisted Synthesis of a Very Large Octameric Hydrogen‐Bonded Capsule

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Synthesis of Enantiopure C₃‐Symmetric Triangular Molecules