Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• , or azacrown ethers 8, with a certain number of nitrogen atoms instead of oxygen in the macrocycle. A combination of both, triaza crown ether, with alternating nitrogen and oxygen atoms in the ring (8b), can be employed to enhance the selectivity for ammonium ions in comparison to potassium ions. It

• salts with binding affinities Kass up to 4.8 × 105 M−1 in CH2Cl2 with 0.25% CH3OH. The bpy-crown macrocycle with n = 1, reflecting the pseudo 18-crown-6 type structure, exhibited the best properties and the highest enantioselectivity towards the S-enantiomer of phenylglycine methyl ester hydrochloride

• for the potassium salt of S-Phe. The cavity of the macrocycle plays an important role in recognition: A dibenzo substitution on the diazacrown ether may close the cavity due to steric hindrance of the arene units on the ring and the resulting π–π-interaction between the two aromatic moieties on the

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• alternating α,α-trehalose motifs and semi-rigid thiourea segments (cyclotrehalans, CTs) [77][78][79][88][89]. Molecular diversity was introduced at the inter-saccharide connectors by exploiting the chemistry of macrocyclic carbodiimides [77][78][79][88][89] as well as by varying the size of the macrocycle

Templated versus non-templated synthesis of benzo-21-crown-7 and the influence of substituents on its complexing properties

• Wei Jiang and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2010, 6, No. 14, doi:10.3762/bjoc.6.14

• ][18][19][20][21][22]. Recently, Huang and co-workers reported that the macrocycle size for forming pseudorotaxane can be reduced to only 21 atoms, namely benzo-21-crown-7 [23] (C7; Scheme 1) and pyrido-21-crown-7 [24], which could still slip over a secondary dialkylammonium ion when one of the alkyl

• property of C7 is more susceptible to modification probably because the smaller macrocycle is more or less rigidified after complexation with secondary dialkylammonium, thus weakening its adjustability. This has to be taken into account if one desires to construct more complex interlocked assemblies by

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• of intramolecular hydrogen bonds. Moreover, we were able to minimize structures for the complexes formed between both receptors and n-C6H13CO-D-Ala-D-Ala-NH2 in which the dipeptide is threaded through the macrocycle (Figure 3). In these minimized structures, the hydrogen-bonding groups of the

• receptor converge toward the center of the macrocycle. The macrocycle is large enough to accommodate the threading dipeptide without incurring any substantial steric clashes. We also observed appropriate complementarity between the hydrogen-bonding groups of substrate and receptor (Figure 3). The analysis

• macrocycle, also allows for the possibility of binding short amino acid sequences not necessarily located on the edges of larger peptides. Other considerations, apart from preventing intramolecular hydrogen bond formation, related to the use of bis(alanyl)benzophenone rigid linkers include: a) to avoid

An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III) ions

• Markus Albrecht,
• Olga Osetska,
• Thomas Abel,
• Gebhard Haberhauer and
• Eva Ziegler

Beilstein J. Org. Chem. 2009, 5, No. 78, doi:10.3762/bjoc.5.78

• opposite helicities (Λ and Δ) and the three isobutenylidene spacers can adopt two different orientations relative to the macrocycle: the CH2 units of the spacers point to the interior of the molecule in the case of the conformers (Λ1)-1b·La and (Δ1)-1b·La and to the exterior in the case of the conformers

Versatile supramolecular reactivity of zinc-tetra(4-pyridyl)porphyrin in crystalline solids: Polymeric grids with zinc dichloride and hydrogen-bonded networks with mellitic acid

• Sophia Lipstman and
• Israel Goldberg

Beilstein J. Org. Chem. 2009, 5, No. 77, doi:10.3762/bjoc.5.77

• with two axial ligands on both sides of the porphyrin macrocycle). In the five-coordinate case, the ZnTPyP assemblies are either 1D chain-polymeric or 0D square-oligomeric, whereas in the six-coordinate case, they form either 3D honeycomb architectures or 2D square-grid networks [17][18][19

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• macrocycles. Keywords: axially chiral biaryl; isoplagiochin; macrocycle; ring strain; total synthesis; Introduction The cyclic bisbibenzyls isoplagiochin C (1) and D (2) were isolated from the liverworts Plagiochila fruticosa [1], Plagiochila deflexa [2], Herbertus sakuraii [3] and Lepidozia fauriana [4

• could be obtained more straightforwardly and in higher overall yield directly from the bromoarene 16 and the arylboronate 26. Indeed, the cyclization of 28 to the macrocycle 7 bearing an “alkyne bridge” was successful in moderate yield using a McMurry protocol (Scheme 7) [32]. Hydrogenation of the

• was obligatory to prevent exclusive pinacolborane reduction. ddppf: 1,1′-bis(diphenylphosphino)ferrocene. Synthesis of the tolane precursors 27 and 28 for cyclization. Synthesis of the modified macrocycles 5–7 from the dialdehyde precursors 28–30. Synthesis of the known macrocycle 3 via McMurry

The first direct synthesis of β-unsubstituted meso- decamethylcalix[5]pyrrole

• Luis Chacón-García,
• Lizbeth Chávez,
• Denisse R. Cacho and
• Josue Altamirano-Hernández

Beilstein J. Org. Chem. 2009, 5, No. 2, doi:10.3762/bjoc.5.2

• ; calix[n]pyrrole; Results and Discussion Calix[n]pyrroles have attracted attention because of their ability to recognize anions [1][2]. To date, the calix[4]pyrroles have been studied the most, in part due to the ease with which the macrocycle can be obtained by the condensation of pyrrole with a ketone

• acetate with 40% yield [6][7]. On the other hand, β-unsubstituted calix[5]pyrroles have been obtained by two routes: a) from the corresponding meso-decamethylcalix[5]furan, via a method analogous to that reported for calix[6]pyrroles, with 1% yield; and b) directly when the macrocycle is covalently bound

• the method described here—namely that bismuth is relatively non-toxic, the macrocycle is obtained in moderate yield, and the synthesis proceeds without any intermediates—make it the best route to β-unsubstituted meso-decamethylcalix[5]pyrrole reported to date. Experimental meso-Decamethylcalix[5

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• ][22]. Recently, we could show that shape-persistent macrocycles with fixed intraannular side chains (e.g. 1) can also exhibit liquid crystalline behavior [23][24]. Compound 1 is a shape-persistent macrocycle which is based on the phenylene-ethynylene-butadiynylene backbone. As it generally holds for

• compared to macrocycle 1. 3,5-Diiodo-4-methylbenzene (2) was treated with trimethylsilyl(TMS)acetylene under standard Hagihara-Sonogashira coupling conditions and subsequently deprotected with K2CO3 in MeOH/THF. As expected, the Pd-catalyzed coupling reaction runs under milder conditions and with higher

• substituents on the phase behavior of these macrocycles [29][30]. A PAH has previously been incorporated into a shape-persistent macrocycle as a part of the rigid backbone [26]. The investigation of the thermal behavior of that compound led to the indication that PAHs could stabilize the thermotropic

Molecular recognition. 1. Crystal structures of hexaazamacrocyclic amines containing p-xylylene spacers and their adducts with acids

• Teresa Borowiak,
• Grzegorz Dutkiewicz,
• Maciej Kubicki,
• Marek Pietraszkiewicz,
• Agnieszka Gil and
• Rainer Mattes

Beilstein J. Org. Chem. 2005, 1, No. 16, doi:10.1186/1860-5397-1-16

• of 1 with hydrochloric or hydrobromic acids,[6][13] with all twelve N-H bonds directed out of the macrocycle. Six of them are roughly normal to the macrocyclic ring whereas the other six are located approximately in the average plane of the macrocycle and hence the cation acts as a twelve-fold donor

• from those which were found in crystals of 1 with HCl, HBr and o-nitrophenol. It clearly shows that the macrocycle adjusts its conformation in order to optimize Coulombic interactions with the dianion of fumaric acid. Thus, as in the previous examples,[6][13] the supramolecular structure is organized

• height of one sheet corresponds to the height of the macrocycle, i.e. about 12 Å. The molecular conformation of 1-N-Me, atom labeling scheme indicated. Displacement parameters are drawn at 50% probability level. The unit cell of 1-N-Me, stacks of molecules are indicated. Formulas of macrocyclic amines, 1