Synthesis of homochiral tetrahydropteridines

A synthesis of protected homochiral tetrahydropteridines from (2S)-malic acid has been developed. This presents methodology for the synthesis of reduced pteridine coenzymes and pharmaceuticals.     

Multiferroic homochiral metal-organic framework

The hydrothermal reaction of (L)-ethyl lactate (Lig-Et) with Tb(ClO(4))(3).6H(2)O gives colorless block (Lig)(2)Tb(H(2)O)(2)(ClO(4)) (1), in which 1 displays a laminar 2D framework. Ferroelectric and magnetic property measurements reveal that 1 probably is the first example of two "ferroic" metal-organic frameworks. Ferroelectricity of its analogue, (Lig)(2)Tb(D(2)O)(2)(ClO(4)) (2), further confirms the presence of the ferroelectric deuterium effect.     

Highest-Tc single-component homochiral organic ferroelectrics

Organic single-component ferroelectrics with low molecular mass have drawn great attention for application in organic electronics. However, the discovery of high-T_c single-component organic ferroelectrics has been very scarce. Herein, we report a pair of homochiral single-component organic ferroelectrics (R)-10-camphorsulfonylimine and (S)-10-camphorsulfonylimine under the guidance of ferroelectric chiral chemistry. They crystallize in the chiral–polar space group P2₁, and their mirror image relations have been identified using vibrational circular dichroism spectra. They both exhibit 422F2 multiaxial ferroelectricity with T_c as high as 429 K. Besides, they possess superior acoustic impedance characteristics with a value of 2.45 × 10⁶ kg s⁻¹ m⁻², lower than that of PVDF. To our knowledge, enantiomeric (R and S)-10-camphorsulfonylimine show the highest T_c among the known organic single-component ferroelectrics and low acoustic impedance well matching with that of bodily tissues. This work promotes the development of high-performance organic single-component ferroelectrics and is of great inspiration to explore their application in next-generation flexible smart devices.

A pair of enantiomeric organic ferroelectrics (R and S)-10-camphorsulfonylimine show the highest T_c among the known single-component organic ferroelectrics.     

Polymorphism in homochiral zinc phosphonates

This paper reports four homochiral zinc phosphonates, alpha-(S)-[Zn 2(pemp)(pempH)Cl] (1), alpha-(R)-[Zn 2(pemp)(pempH)Cl] (2), beta-(S)-[Zn 2(pemp)(pempH)Cl] (3), and beta-(R)-[Zn 2(pemp)(pempH)Cl] (4) [pempH 2 = (1-phenylethyl)amino]methylphosphonic acid]. Both 1 and 2 are enantiomers, crystallizing in an orthorhombic P2(1)2(1)2(1) space group, while 3 and 4 are polymorphic phases of 1 and 2, respectively, crystallizing in a monoclinic P2(1) space group. The polymorphism is induced by temperature or additional organic molecules.     

Metal-complex-decorated homochiral heterobimetallic telluride single-stranded helix

Solvothermal reaction of a mixture of Sn, Mn, and Te at 200 degrees C using teta as the solvent yields a novel inorganic-organic hybrid solid [Mn(teta)(en)].[Mn(teta)][Mn(SnTe4)2.Mn(teta)] (teta=triethylenetetramine and en=ethylenediamine; 1), which has a homochiral single-stranded helical structure. The material is a semiconductor with a band gap of 0.88 eV and shows paramagnetic behavior between 2 and 300 K.     

Synthesis of homochiral pentadentate sulfonamide-based ligands

A two-step synthesis of pentadentate, tetraionic ligands based on sulfonamide, amide, and pyridyl groups is reported. These ligands are easily accessible in good to excellent yield from commercially available materials.     

Negatively-charged halide adducts of homochiral serine octamers

Negatively charged halide adducts of serine octamers, (Ser(8)+2Cl)(2-) and (Ser(8)+2Br)(2-), appear as magic number clusters in the negative ion electrospray mass spectra of solutions containing serine and the halide. Like the well-known protonated serine octamer, these negatively charged adducts are formed with homochiral preference and also undergo chiroselective substitution reactions with other amino acids. Tandem mass spectra of negatively charged halide adducts of serine octamers show that these ions also have a characteristic fragmentation signature. The fact that octamers of both polarities display analogous chemical properties suggests that these may be characteristics of the so-far-unknown neutral octamer. If serine played a key role in the origin of homochirality on the primitive earth, it was likely through both the neutral octamer and the ionic adducts. Unlike the octamers, the formation of halide-containing serine cluster ions of particular sizes is unfavorable under the conditions of the experiment. Signals corresponding to the ions (Ser(9)+2Br)(2-) and (Ser(15)+2Br)(2-) are particularly low in intensity, giving rise to gaps in the distribution of serine/bromide clusters in the negative ion electrospray mass spectra. These cluster sizes are likely to correspond to unstable "anti-magic number" clusters recently reported by Clemmer.     

An efficient approach to homochiral indane nucleosides

A series of new chiral 6-substituted purinyl and 8-aza-purinyl carbonucleosides based on indanol were synthesized from the commercially available (1R,2S)-1-amino-2-indanol and (1S,2R)-1-amino-2-indanol based on a well-known methodology.     

Parallel synthesis of homochiral β-amino acids

The parallel asymmetric synthesis of an array of 30 β-amino acids of high enantiomeric purity using the conjugate addition of homochiral lithium N-benzyl-N-(α-methylbenzyl)amide as the key step is accomplished. The experimental simplicity and highly practical nature of the protocol is demonstrated by the efficient parallel conversion of 15 α,β-unsaturated esters to both enantiomeric series of the corresponding β-amino acids in high overall yields and selectivities with minimal purification involved in each step of the reaction protocol.     

Hierarchical assembly of two-dimensional homochiral nanocavity arrays

We demonstrate the rational design of nanoporous two-dimensional supramolecular structures by the hierarchical assembly of organic molecules and transition metal atoms at surfaces. Single-molecule level observations with scanning tunneling microscopy monitor the successive aufbau of structures with increasing complexity. From the primary components secondary mononuclear chiral complexes are formed, which represent antecedents for tertiary polynuclear metal-organic nanogrids. These nanogrids represent the constituents of the eventually evolving two-dimensional networks comprising homochiral nanocavity arrays. Our findings visualize the evolution of complex matter in an exemplary way: from per se achiral species via chiral intermediates to mesoscale dissymmetric structures.     

The cycloaddition of nitrones with homochiral cyclopropanes

The cycloaddition of nitrones and enantiomerically pure cyclopropane-1,1-dicarboxylates is examined. Transfer of optical activity to the adduct is dictated by thermal reaction conditions and nature of cyclopropane substitution. Optically active 2-substituted cyclopropane-1,1-dicarboxylates are shown to racemize under typical reaction conditions, providing evidence for a zwitterionic ring-opened intermediate.     

Evolution of synthetic routes towards homochiral Tapentadol

Analysis of the literature shows that the development of synthetic approaches to Tapentadol, an agonist of the μ-opioid receptor and norepinephrine reuptake inhibitor, has followed four, partially overlapping, phases. The most advanced approaches, based on stereoselective syntheses, appeared only after 2010. The majority of the chemistry examples presented in this review come from patent applications and as such have not been subjected to rigorous peer review, but may serve well as an inspiration to organic chemists for solving analogous synthetic problems.     

Stereoselective intramolecular cycloadditions of homochiral N-alkenoyl aryl azides

Starting from the commercially available (S)-1-phenylethylamine and l-alanine benzylester, we synthesised the homochiral N-alkenoyl aryl azides 2a–2d. The intramolecular cycloaddition of unsubstituted 2a and 2b gave enantiopure 3,3a-dihydro-1,2,3-triazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones 3a, 3b, 4a and 4b, while phenyl-substituted 2c and 2d gave enantiopure 1,1a-dihydro-2H-azirino[2,1-c][1,4]benzodiazepine-4(6H)-ones 5c, 5d, 6c and 6d.     

Synthesis and structure of homochiral polymeric praseodymium tartrate

The homochiral metal-organic coordination polymer of the composition [{Pr(H₂O)₂}₂-(d-tart)₃]·H₂O was synthesized by heating an aqueous solution of praseodymium(III) chloride and d-tartaric acid (d-H₂tart) in the presence of KOH. The crystal structure of the polymer was determined by X-ray crystallography and confirmed by IR spectroscopy, thermogravimetry, and elemental analysis.     

Asymmetrization of meso-cyclic ketones using homochiral acetal templates

Employing the homochiral acetal template, asymmetrization of meso-substituted cyclohexanones is explored. By the use of optically-active 2,4-pentanediol as a chiral protecting group, highly diastereoselective acetal cleavage is achieved when treated with organoaluminum reagent. Dialkylaluminum amides are also effective reagents for this reaction.     

Asymmetric synthesis of beta-amino-gamma-substituted-gamma-butyrolactones: double diastereoselective conjugate addition of homochiral lithium amides to homochiral alpha,beta-unsaturated esters

Chiral alpha,beta-unsaturated esters, containing a single, gamma-stereogenic centre, show modest levels of substrate control upon conjugate addition of lithium dibenzylamide. Double diastereoselective conjugate additions of homochiral lithium N-benzyl-N-(alpha-methylbenzyl)amide to the homochiral alpha,beta-unsaturated esters display "matching" and "mismatching" effects. In each case, however, these additions proceed under the dominant stereocontrol of the lithium amide to give the corresponding beta-amino esters in high de. A remarkable reversal in stereoselectivity is noted by changing the ester functionality to an oxazolidinone. Subsequent O-deprotection and cyclisation of the resultant beta-amino adducts gives access to the corresponding beta-amino-gamma-substituted-gamma-butyrolactones in good yield and high de.     

A homochiral metal-organic framework membrane for enantioselective separation

For the first time, a homochiral metal-organic framework membrane was prepared for the enantioselective separation of important chiral compounds, especially chiral drug intermediates, which will allow for the potential development of a new, sustainable and highly efficient chiral separation technique.     

Dielectric anisotropy of a homochiral rare-earth metal complex

A homochiral rare-earth metal Tb complex that exhibited a very large dielectric anisotropic property with a temperature-independent feature is obtained. Our findings on high-dielectric anisotropy will provide a new impetus in this field of materials science.