新型鹅去氧胆酸分子裂缝的设计合成

分子识别是生物体系的基本特征,并在生命活动中起中心作用。生物酶高效专一地催化生化反应,抗体与抗原的结合,蛋白质分子与DNA序列的相互作用等都源于精确的分子识别[1,2]。利用合成的人工受体与适当底物之间的分子识别以建立仿生仿酶模型的研究,已成为生物有机化学前沿富有挑战性的领域。分子裂缝作为一类新型的人工受体,以其灵活的结构以及易于将功能团聚集在受体与底物结合的活性部位上等优点,引起了人们的广泛关注[3-5]。胆甾因其具有刚性的凹面结构和天然的手性,是构筑分子裂缝人工受体的理想结构单元。我们曾报道3α-OH和7α-OH同…     

氨基甲酸酯型脱氧胆酸分子钳对氨基酸甲酯的手性识别 研究

以脱氧胆酸为spacer,通过三光气桥连各种芳胺,合成了新的氨基甲酸酯型分子钳受体1～4,这些化合物的结构经IR,^1HNMR和元素分析所证实。利用差光谱滴定法考察了其与D/L氨基酸甲酯的对映选择性识别性能。结果表明,分子钳1～4对所考察的氨基酸甲酯均具有识别能力,其对D-氨基酸甲酯的识别优于对L-氨基酸甲酯的识别。从主客体间的大小形状匹配及几何互补关系等方面对这些受体的识别能力及对映选择性进行了讨论。     

新型鹅去氧胆酸分子钳的设计合成和分子识别性质研究

以鹅去氧胆酸为隔离基, 芳香族化合物为手臂设计合成了一类新型的分子钳, 其结构经¹H NMR, IR, MS及元素分析确证. 利用紫外光谱滴定法考察了其与D/L氨基酸甲酯的对映选择性识别性能. 结果表明, 分子钳3a～3e对所考察的氨基酸甲酯均具有识别能力, 其对L-氨基酸甲酯的识别优于对D-氨基酸甲酯的识别. 从主客体的大小形状匹配及几何互补关系等方面对这些受体的识别能力及对映选择性进行了讨论.     

Hydrogen-bonding-driven preorganized zinc porphyrin receptors for efficient complexation of C60, C70, and C60 derivatives

This paper describes the self-assembly of a new class of foldamer-based molecular tweezers, whose rigid folded conformations are stabilized by intramolecular hydrogen bonding. Two zinc porphyrin units are introduced to the ends of molecular tweezers Zn(2)1 and Zn(2)2, while three zinc porphyrin units are incorporated to the S-shaped bi-tweezers Zn(3)3, which may be regarded as a combination of two Zn(2)1 molecules. Due to the preorganized U-shaped feature, Zn(2)1 and Zn(2)2 are able to strongly complex C60, C70, and C60 derivative 25 in chloroform or toluene in a 1:1 binding stoichiometry, whereas Zn(3)3, which possesses two tweezer units, complexes the guests in a 1:2 stoichiometry. More stable complex Zn(3)3.24 is formed between Zn(3)3 and 24, a linear molecule bearing two C60 moieties at the ends, as a result of the cooperative interaction of two binding sites. Chiral induction is observed for all the three receptors upon complexation with C60-incoporated chiral phenylalanine derivative 29, although the complexation of 29 by the folding receptors is pronouncedly weaker than that of C60 and 25 due to increased steric hindrance. The driving force for the formation of the complexes is the well established pi-pi stacking between the zinc porphyrin and fullerene units. The 1H and 13C NMR, UV-vis, fluorescent, and circular dichroism spectroscopy have been used to investigate the complexing behavior of the folding receptors and the fullerene guests. The association constants of the corresponding complexes in toluene and chloroform (if possible) have been evaluated with the UV-vis and fluorescent titration experiments.     

The Role of Amino Acid Esters and the Amide Group in the Chiral Induction Process by a Novel Monoamide‐Linked Monozinc Bisporphyrinate

A monoamide‐linked monozinc bisporphyrinate for monodentate chiral guests was designed and synthesized. It was used as a host to complex with amino acid esters; the resulting CD spectra showed typical bisignate shape, which suggest the ability to transfer chirality from amino acid esters. The molecular structure of the host indicates that amino acid esters function as monodentate ligands in the host‐guest complex. ¹H NMR spectroscopic studies suggest formation of a hydrogen bond between the amide NH and the carbonyl oxygen groups of the amino acid ester. The possible mechanism of the chiral induction process was further studied by DFT calculations.     

单手性臂脱氧胆酸分子裂缝的设计与微波合成

以脱氧胆酸甲酯为隔离基 ,3位构建为非手性单元 ,在 12位引入手性单元 ,合成具有不同手性中心和裂穴的新型单手性臂分子裂缝受体 .结构均经1 HNMR ,IR ,MS及元素分析所确证 ,并且考察了其对中性小分子和D/L 氨基酸甲酯的识别性能 .初步研究表明 ,这类裂缝型受体不仅对中性小分子具有优良的识别性能 ,而且对D/L 氨基酸甲酯具有良好的手性识别能力 .     

Self-assembly of chiral molecular polygons

Treatment of 2,2'-diacetyl-1,1'-binaphthyl-6,6'-bis(ethyne), L-H2, with 1 equiv of trans-Pt(PEt3)2Cl2 led to a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(L)]n (n = 3-8, 1-6). Each of the chiral molecular polygons 1-6 was purified by silica gel column chromatography and characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, MS, IR, UV-vis, and circular dichroism spectroscopies, and microanalysis. The presence of tunable cavities (1.4-4.3 nm) and chiral functionalities in these molecular polygons promises to make them excellent receptors for a variety of guests.     

新型酯键型鹅去氧胆酸分子钳的设计合成

以鹅去氧胆酸为隔离基、芳香族化合物为手臂设计合成了一类新型的分子钳, 其结构经¹H NMR, IR, MS和元素分析确证, 并且考察了其对D/L-氨基酸甲酯的对映选择性识别性能. 初步的结果表明, 这类手性分子钳对D-氨基酸甲酯有较好的识别性能.     

Stereodynamics of N-isopropyl-N-methylpropargylamine. Dynamic NMR studies. Molecular mechanics calculations.

N-Isopropyl-N-methylpropargylamine (N-isopropyl-N-methyl-2-propyn-1-amine; IMPA) is chiral at the pyramidal nitrogen. Racemization occurs via an inversion-rotation process. Both 13C(1H) and 1H dynamic NMR (DNMR) spectra decoalesce in response to slowing inversion-rotation (delta G++ = 7.7 +/- 0.1 kcal/mol). While aspects of the DNMR spectra suggest the presence of minor conformations, the spectrum at 100 K shows a strong preference for one conformation. The NMR data suggest that the preferred conformation has both the isopropyl methine proton and the ethynyl group anti to the lone pair. Both isopropyl methyl groups are gauche to the lone pair. This conformational preference is in significant contrast to N-ethyl-N-methyl-2-aminopropane in which the population of that conformation having the ethyl methyl group and the isopropyl methine proton both anti to the lone pair is only 5% at 95 K. The NMR data, supported by molecular mechanics (MMX) calculations, suggest a special stabilization for the ethynyl group being oriented anti to the lone pair.     

新型手性Salen双核锌配合物的分子识别研究

合成了新型手性Salen配体（H3L）及新型手性Salen双核锌配合物（主体）.通过研究主体对咪唑类客体及氨基酸酯类客体的分子识别行为,测定了这些配位反应的缔合常数.主体对咪唑类客体分子识别的缔合常数顺序为:K(Im) >K(2-MeIm) >K(2-Et-4-MeIm).主体对氨基酸酯类客体分子识别的缔合常数顺序为:K(LeuOCH3) >K(ValOCH3) >K(AlaOCH3) >K(SerOCH3),配位数均为2.主体与D、 L型氨基酸酯分子识别反应在不同温度下的缔合常数结果表明,随着温度的升高,对映选择性下降.实验发现反应体系中存在焓熵补偿关系. CD光谱的研究结果也反映了主体对不同客体识别能力的差异.     

Chiral clusters in a supersonic beam: R2PI-TOF spectroscopy of diastereomeric carboxylic esters/(R)-(+)-1-phenyl-1-propanol complexes

Wavelength and mass resolved resonance-enhanced two photon ionization (R2PI) excitation spectra of (R)-(+)-1-phenyl-1-propanol (P(R)) and its complexes with some chiral esters, i.e. methyl lactates (L(R) and L(S)), methyl 3-hydroxybutyrates (H(R) and H(S)), and methyl 2-chloropropionates (C(R) and C(S)), have been recorded after a supersonic molecular beam expansion and interpreted in the light of DFT calculations. The spectral features of the selected complexes were found to depend on the nature of hydrogen-bond interactions within the diasteromeric complexes, whose intensity in turn depends upon the structure and the configuration of the estereal moiety. The study further confirms resonant two-photon ionization spectroscopy, coupled with time-of-flight mass resolution (R2PI-TOF), as an excellent tool for gathering valuable information on the interactive forces in molecular clusters and for the enantiodiscrimination of chiral molecules in the gas phase.     

新型脱氧胆酸类手性不对称脲分子钳的设计合成

以刚性的脱氧胆酸甲酯为隔离基, 在其3位连接苯甲酰基, 12位连接手性不对称脲, 设计合成了一类新型的手性分子钳. 其结构均经1H NMR, IR, MS和元素分析确证, 并且考察了其对中性分子和D/L-氨基酸甲酯的识别性能. 实验结果表明, 这类分子钳人工受体不仅对中性有机小分子具有良好的识别能力, 而且对D/L-氨基酸甲酯亦具有优良的对映选择性识别性能.     

α-猪去氧胆酸类分子钳的设计合成

以α-猪去氧胆酸为隔离基，芳香族化合物为手臂设计合成了一类新型的酯键 型分子钳，结构均经^1H NMR，IR,MS及元素分析所确证，并且考察了其对芳香胺类 化合物和D／L-氨基酸甲酯的识别性能．初步研究结果表明，这类分子钳受体不但 对中性小分子具有识别性能，而且对D／L-氨基酸甲酯具有对映选择性识别性能．     

The prediction of the absolute stereochemistry of primary and secondary 1,2-diols by 1H NMR spectroscopy: principles and applications

The absolute configuration of 1,2-diols formed by a primary and a secondary (chiral) hydroxyl group can be deduced by comparison of the 1H NMR spectra of the corresponding (R)- and bis-(S)-MPA esters (MPA = methoxyphenylacetic acid). This method involves the use of the chemical shifts of substituents L1/L2 attached to the secondary (chiral) carbon, and of the hydrogen atom linked to the chiral center (C alpha-H) as diagnostic signals. Theoretical (AM1, HF, and B3 LYP calculations) and experimental data (dynamic and low-temperature NMR spectroscopy, studies on deuterated derivatives, constant coupling analysis, circular dichroism (CD) spectra, and NMR studies with a number of diols of known absolute configuration) prove that the signs of the delta delta(RS) obtained for those signals correlate with the absolute configuration of the diol. A graphical model for the reliable assignment of the absolute configuration of a 1,2-diol by comparison of the NMR spectra of its bis-(R)- and bis-(S)-MPA esters is presented.     

Design and synthesis of chiral single-armed molecular tweezers derived fromα-hyodeoxycholic acid

A novel type of molecular tweezers with different chiral center and cleft has been designed and prepared by usingα-hyodeoxycholic acid as spacer and D/L-amino acid methyl ester as chiral arm attached at 3-position.Their structures were elucidated by ~1H NMR,FTIR and elemental analysis.Their recognition properties for various D/L-amino acid methyl esters were also investigated.The preliminary results indicated that these chiral single-armed molecular tweezers exhibited good recognition ability for D/L-ami...     

联苯二甲酸类手性分子钳的微波合成

在微波辐射条件下, 以联苯二甲酸为间隔基, L-氨基酸甲酯为手臂, 合成了7个新型手性分子钳. 其结构经¹H NMR, IR, MS和元素分析所证实. 与常规加热的一般合成方法相比, 该法明显地提高了反应速度和产率. 初步的实验结果表明, 这类分子钳人工受体对D/L-氨基酸甲酯具有良好的对映选择性识别性能.     

a,a,a,b-ZnT(o-BocThr)APP对咪唑衍生物和氨基酸酯的分子识别研究

Molecular Recognition of α,α,α,β-ZnT（o-BocThr）APP （1） toward a series of imidazole derivatives and amino acid esters was investigated. Association constants were determined in chloroform by means of UV-Vis titration method. The association constants of 1 with imidazole derivatives are larger than those of 1 with amino acid esters. 1H NMR spectra were investigated to describe the binding mode of the recognition system, showing that all the protons of the guests were shifted to upfield. The circular dichroism spectra of 1-L-/D-ValOMe showed a split cotton effect in Soret region, while those of 1-L-/D-PheOMe showed no split cotton effect. Molecular modeling was performed to understand chiral recognition on a molecular level. Quantum chemical calculation was carried out based on the stable conformations of these recognition systems, which gave a reasonable explanation for the behavior of molecular recognition. The results indicated that the conformation of 1-D-ValOMe was more stable than that of 1-L-ValOMe.     

Synthesis and chiral recognition properties of two novel chiral calix[4]arene tartaric ester derivatives

Two new chiral calix[4]arene derivatives containing tartaric acid ester moieties were synthesized. The chiral calix[4]arenes are in a ‘cone’ conformation according to NMR spectroscopy. The chiral recognition capabilities of 1–4 toward the guests, 1,2-propanediol and serine methyl ester hydrochloride (SerOMe), were investigated (¹H NMR spectroscopy). The extraction properties of compounds 1 and 2 toward selected α-amino acid methyl esters were also studied.     

‘Two-point’-bound supramolecular complexes from semi-rigidified dipyridine receptors and zinc porphyrins

Two linear compounds 1 and 2 have been designed and synthesized as new receptors for zinc porphyrins. Both compounds consist of two folded aromatic amide moieties, which are connected with an acetylene linker in 1 or directly in 2. The rigid conformations of their folded moieties are stabilized by intramolecular tri-centered hydrogen bonding, while the whole molecule adopts a ‘S’- or ‘C’-styled conformation depending on the relative orientation of the two rigid moieties. Two pyridine units are introduced at the ends of 1 and 2 for the complexation of zinc porphyrin guests. Although the ¹H NMR investigation indicated that both compounds can bind two zinc porphyrin guests at high concentrations (≥5 mM) in chloroform, the UV-vis studies revealed that, at low concentration of 1 and 2 (4 μM), both compounds complex one zinc porphyrin guest to form structurally unique ‘two-point’-bound 1:1 complexes. The association constants of the 1:1 complexes have been determined with the UV-vis titration experiments.     

Self-assembly of achiral and chiral macrocyclic ligands: synthesis,protonation constants,conformation and asymmetric catalysis

New 30-membered achiral and chiral polyaza macrocyclic ligands, L1 and L2 were synthesized directly from [3 + 3] condensation of phthalic dicarboxaldehyde with cis- and (1R,2R)-diaminocyclohexane, respectively. The trimeric macrocyclic structures were confirmed by electrospray ionization mass spectrometry (ESI-MS), 1H NMR, 13C NMR spectroscopy and elemental analysis. Potentiometry was used to determine the protonation constants of the ligands. UV-vis spectrophotometric titration was employed to investigate the coordination and conformational properties of the chiral ligand (L2). Direct enantioselective aldol reaction has been successfully performed using 4-nitrobenzaldehyde and acetone in the presence of the chiral macrocycle and its zinc(II) complexes as catalysts.