Synthetic Methods for the Preparation of Conformationally Restricted Analogues of Nicotine

In the context of naturally occurring nitrogen heterocycles, nicotine is a chiral alkaloid present in tobacco plants, which can target and stimulate nicotinic acetylcholine receptors (nAChRs), a class of ligand-gated ion channels commonly located throughout the human brain. Due to its well-known toxicity for humans, there is considerable interest in the development of synthetic analogues; in particular, conformationally restricted analogues of nicotine have emerged as promising drug molecules for selective nAChR-targeting ligands. In the present mini-review, we will describe the synthesis of the conformationally restricted analogues of nicotine involving one or more catalytic processes. In particular, we will follow a systematic approach as a function of the heteroarene structure, considering: (a) 2,3-annulated tricyclic derivatives; (b) 3,4-annulated tricyclic derivatives; (c) tetracyclic derivatives; and (d) other polycyclic derivatives. For each of them we will also consider, when carried out, biological studies on their activity for specific nAChR subunits.     

Design and Synthesis of Lipids Bearing Nucleosides as Gene Vectors

Delivery of exogenous DNA into cells of various origins plays an important role not only in basic research, but also in clinical application in gene therapy. Great efforts have been made towards the development of viral and nonviral vectors for these purposes1~6. However, at the present stage, none of the vectors can claim to be the panacea. Although most viral vectors can transfer gene efficiently and some of them can be used for gene transfer into tissue cells in vivo, they suffer from immu…     

复分解反应在核苷类似物合成中的应用

核苷类似物可以参与并干扰细菌（病毒）的DNA或RNA过程,抑制其生长和繁殖,从而有希望发展为抗肿瘤抗病毒药物。一些天然的核苷化合物虽然表现出一定的生理活性,在体内缺乏酶稳定性和靶向选择性却限制了其在医药领域的应用,合成具有生物活性的化学修饰的核苷及其衍生物是核酸药物化学中的重要课题。一类在金属卡宾复合物催化下的分子内或分子间烯烃重组反应-----复分解反应的发展使核苷类似物的合成进入了新阶段, 烯烃复分解反应成为核苷类似物合成的主要途径之一。随着施洛克催化剂、格拉布催化剂等复分解反应催化剂的发现和不断改进,烯烃复分解反应,尤其是关环复分解和交叉复分解反应被广泛应用于构建核苷类似物的糖环(或伪糖)结构或连接核苷类似物单体而形成核苷多聚物。本文对烯烃复分解反应在核苷类似物包括碳环核苷,2’,3’-双脱氧核苷,无环核苷,多环核苷及核苷二聚体或三聚体的合成中的应用进行了综述。     

碳环核苷的合成研究进展

碳环核苷是一类结构特殊且具有多种生物活性, 其中特别是抗病毒活性的核苷衍生物. 目前, 碳环核苷的合成及生物活性筛选已成为新药研究领域的热点之一. 综述了近年来各类碳环核苷的合成研究进展, 并对不同合成路线作了简要分析和评论.     

Synthesis and Crystal Structure of N-[1-（2-Methyl-1-methylcarbamoyl- propylcarbamoyl）-2,3-diphenyl- cyclopropyl]-benzamide

N-[1-（2-Methyl-1-methylcarbamoyl-propylcarbamoyl）-2,3-diphenyl-cyclopropyl]-ben- zamide, C29H31N3O3, has been synthesized and characterized by IR, ^1H NMR, ^13C NMR and singlecrystal X-ray diffraction. The crystal is of orthorhombic, space group P212121 with a = 11.0855（11）, b = 18.7756（19）, c = 24.434（2）A, V = 5085.5（9）A^3, Z = 8, Mr = 469.57, Dc = 1.227 g/cm^3, λ = 0.71070 A,μ（MoKα） = 0.080 mm^-1, F（000） = 2000, the final R = 0.0579 and wR = 0.1111 for 4569 observed reflections with I 〉 2σ（I）. The N-H and oxygen atom are involved in intermolecular hydrogen bonds which link the molecules into a one-dimensional chain.     

Synthesis,Crystal Structure and Bioactivity of N-Phenethyl-4-hydroxy-4-phenyl Piperidine Hydrochloride

A novel compound N-phenethyl-4-hydroxy-4-phenyl piperidine hydrochloride （C19H24ClNO·H2O） has been synthesized and structurally characterized by elemental analysis, IR, ^1H NMR spectra and single-crystal X-ray diffraction. The crystal belongs to orthorhombic, space group P212121 with a = 8.6306（8）, b = 11.0464（10）, c = 19.3221（18）A^°, V = 1842.1（3）A^°^3, Z = 4, Dc =1.211 g/cm^3,μ = 0.217 mm^-1, Mr= 335.86, F（000） = 720, S = 0.973, R = 0.0420 and wR = 0.1009 for 3627 unique reflections with 3157 observed ones （I 〉 2σ（I））. In the crystal, the dihedral angles made by piperidine ring with two benzene rings are 84.8（6） and 62.5（7）°, respectively. Intermolecular O-H…O and O-H…Cl hydrogen bonds involving water molecules form chains along the b axis, which stabilizes the crystal structure. The preliminary bioactivity tests indicated that the title compound has good effect of cellular growth inhibition to K562 cells and potential bioactivity of anti-leukemia.     

Synthesis and Evaluation of Some Uracil Nucleosides as Promising Anti-Herpes Simplex Virus 1 Agents

Since herpes simplex virus type 1 (HSV-1) infection is so widespread, several antiviral drugs have been developed to treat it, among which are uracil nucleosides. However, there are major problems with the current medications such as severe side-effects and drug resistance. Here we present some newly synthesized cyclic and acyclic uracil nucleosides that showed very promising activity against HSV-1 compared to acyclovir.     

Synthesis and Evaluation of Non-Hydrolyzable Phospho-Lysine Peptide Mimics

The intrinsic lability of the phosphoramidate P−N bond in phosphorylated histidine (pHis), arginine (pHis) and lysine (pLys) residues is a significant challenge for the investigation of these post-translational modifications (PTMs), which gained attention rather recently. While stable mimics of pHis and pArg have contributed to study protein substrate interactions or to generate antibodies for enrichment as well as detection, no such analogue has been reported yet for pLys. This work reports the synthesis and evaluation of two pLys mimics, a phosphonate and a phosphate derivative, which can easily be incorporated into peptides using standard fluorenyl-methyloxycarbonyl- (Fmoc-)based solid-phase peptide synthesis (SPPS). In order to compare the biophysical properties of natural pLys with our synthetic mimics, the pK_a values of pLys and analogues were determined in titration experiments applying nuclear magnetic resonance (NMR) spectroscopy in small model peptides. These results were used to compute electrostatic potential (ESP) surfaces obtained after molecular geometry optimization. These findings indicate the potential of the designed non-hydrolyzable, phosphonate-based mimic for pLys in various proteomic approaches.     

Synthesis and Novel Properties of Alkyl Thiophosphoramidate Derivatives of Nucleosides

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Synthesis and Novel Properties of Alkyl Thiphosporamidate Derivatives of Nucleosides

Novel alkyl thiophosphoramidate derivatives of nucleosde analogues(5) have been prepared by phosphochloridothioate chemistry.O-Isopropyl 2‘,3‘-O-isopropylidene uridine-5‘-yl N-thiophosphoryl threonine and serine methyl esters(5a and 5b )underwent the intramolecular catalyzed hydrolysis reaction.     

Noncanonical RNA Nucleosides as Molecular Fossils of an Early Earth—Generation by Prebiotic Methylations and Carbamoylations

The RNA‐world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth.     

Advances in Atroposelectively De Novo Synthesis of Axially Chiral Heterobiaryl Scaffolds

Axially chiral heterobiaryl frameworks are privileged structures in many natural products, pharmaceutically active molecules, and chiral ligands. Therefore, a variety of approaches for constructing these skeletons have been developed. Among them, de novo synthesis, due to its highly convergent and superior atom economy, serves as a promising strategy to access these challenging scaffolds including C-N, C-C, and N-N chiral axes. So far, several elegant reviews on the synthesis of axially chiral heterobiaryl skeletons have been disclosed, however, atroposelective construction of the heterobiaryl subunits by de novo synthesis was rarely covered. Herein, we summarized the recent advances in the catalytic asymmetric synthesis of the axially chiral heterobiaryl scaffold via de novo synthetic strategies. The related mechanism, scope, and applications were also included.     

Synthesis of 5-substituted pipecolic acid derivatives as new conformationally constrained ornithine and arginine analogues

Two, orthogonally protected, constrained analogues of arginine have been synthesised in a diastereodivergent manner. The key step involved an electrophilic or radical functionalisation of methyl N-Boc-5,6-dehydropipecolate.     

Synthesis and biological evaluation of two novel 2′-substituted tiazofurin analogues

Two novel tiazofurin analogues, 2-(2-benzamido-2-deoxy-β-d-ribofuranosyl)thiazole-4-carboxamide 4 and 2-(2-azido-2-deoxy-β-d-ribofuranosyl)thiazole-4-carboxamide 5, have been synthesized starting from d-glucose and evaluated for their in vitro cytotoxicity against several human leukaemia and solid tumour cell lines.     

Synthesis and Characterization of New 1-Methyl-4-(Methylamino)Piperidine and Decahydroquinoline Platinum(II) Complexes Containing Disubstituted Sulfide as a Leaving Group

A series of cationic platinum(II) complexes of the type [Pt(mmap)R'R"S)Cl](NO₃) and [Pt(dhq)₂(R'R"S)Cl]-(NO₃) (where mmap=1-methyl-4-(methylamino)piperidine; dhq=decahydroquinoline; and R'R"S=dimethylsulfide, diethylsulfide, diisopropylsulfide, diphenylsulfide, dibenzylsulfide, methylphenylsulfide or methyl-p-tolylsulfide) has been synthesized and characterized by elemental analysis, infrared, ¹H and ¹⁹⁵Pt nuclear magnetic resonance spectroscopic techniques.     

Synthesis of some substituted triazolo[4,3-b][1,2,4]triazines as potential anticancer agents

The synthesis of some 3-substituted amino-6,7-diphenyl-1,2,4-triazolo[4,3-b][1,2,4]triazines (15) by cyclodesulfurisation of the corresponding N-(5,6-diphenyl-1,2,4-triazin-3-yl)-N-[substituted thio (carbamoyl)]hydrazines (3) using dicyclohexylcarbodiimid (DCC) and mercuric chloride is described. Moreover, trials to prepare 3-substituted amino-7-hydroxy-6-methyl-1,2,4-triazolo[4,3-b][1,2,4]triazines were not successful.

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Synthese einiger substituierter Triazolo[4,3-b][1,2,4]-triazine als potentielle Antikrebswirkstoffe

Zusammenfassung Es wird die Synthese einiger 3-substituierter Amino-6,7-diphenyl-1,2,4-triazolo[4,3-b][1,2,4]-triazine (15) mittels Cyclodesulfurisierung der entsprechenden N-(5,6-Diphenyl-1,2,4-triazin-3-yl)-N-[subst.thio(carbamoyl)]-hydrazine (3) unter Verwendung von Dicyclohexylcarbodiimid (DDQ) beschrieben. Versuche zur Herstellung von 3-substituierten Amino-7-hydroxy-6-methyl-triazolo[4,3-b][1,2,4]-triazinen schlugen fehl.

     

Stereoselective Synthesis of 2,6‐Disubstituted Piperidines Using the Iridium‐Catalyzed Allylic Cyclization as Configurational Switch: Asymmetric Total Synthesis of (+)‐241 D and Related Piperidine Alkaloids

Pressing the configurational switch : Use of enantiomeric Ir catalysts allows the vinylpiperidine building blocks 2 a and 2 b to be synthesized with high selectivity. Total syntheses of the dendrobate alkaloid (+)‐241 D, its C6‐epimer, and a spruce alkaloid are presented as applications.

     

KF/Al2O3 as a Highly Efficient,Green, Heterogeneous,and Reusable Catalytic System for the Solvent-Free Synthesis of Carboacyclic Nucleosides via Michael Addition Reaction

KF/Al₂O₃ acts as an efficient catalytic system for the synthesis of carboacyclic nucleosides via Michael addition of pyrimidine and purine nucleobases to α,β-unsaturated esters under solvent-free and microwave conditions. Using this method, the title compounds are produced in good to excellent yields and short reaction times.