异鸟苷掺人的富鸟嘌呤寡核苷酸的合成

目的 改进异鸟苷单体的合成路线，合成异鸟苷掺入的富鸟嘌呤的寡核苷酸。方法 以6-O-苄基鸟嘌呤为原料，经环氧开环、催化氢化、水解还原制备异鸟苷，经多步反应后得到异鸟苷亚磷酰化产物，采用固相合成方法合成异鸟苷掺入的富含鸟嘌呤的寡核苷酸。结果 与结论经环氧开环能够区域选择性地得到N9取代的单一产物，收率提高到40％，并成功地合成了异鸟苷掺入的富含嘌呤十六聚寡核苷酸。本合成路线具有区域选择性强、路线简单、易操作、收率高等优点。     

2,N-二甲基-N-(3,3-二苯基丙基)-1-氨基-2-丙醇的合成

目的研究2,N-二甲基-N-(3,3-二苯基丙基)-1-氨基-2-丙醇(1)的合成方法.方法以肉桂酸、氯化亚砜、甲胺等为原料,经烃化、氯化、酰化和还原反应得到N-甲基-3,3-二苯基丙胺(5);以3-氯异丁烯为原料,经加成、水解、环合反应得到环氧异丁烷(7),化合物5与7经烃化反应得到目标产物.结果与结论设计的合成路线以肉桂酸计,5步反应总收率为62.7%,合成路线简便易行,适于大规模制备.所合成的目标产物经ESI-MS和1H-NMR确证.     

脱氢氯甲睾酮的合成工艺

目的 合成脱氢氯甲睾酮并改进其工艺.方法 以甲睾酮和H2O2环氧化反应得到环氧甲睾酮,再与盐酸在丙酮溶媒中进行氯化反应,得到氯甲睾酮,最后用2,3-二氯-5,6-二氰基对苯醌在PTS催化下脱氢得到脱氢氯甲睾酮.结果 总收率30%,产物结构经熔点、质谱和核磁共振氢谱确证.结论 此合成路线操作简单可行,有利于工业化生产.     

异核苷掺入寡核苷酸的合成及其与互补序列的结合研究

目的合成异核苷掺入寡核苷酸并考察它们与互补序列的结合能力.方法采用DNA固相合成仪合成寡核苷酸,通过热变性实验考察双链的稳定性.结果合成了四条单异核苷掺入的寡核苷酸,热变性实验结果发现异核苷的引入降低了双链的稳定性,当异核苷处于寡核苷酸链的中央时,这种影响更为明显.异核苷6′-OH处于游离和烯丙基保护状态时的结果没有显著差异.结论寡核苷酸中的异核苷使链发生扭曲,从而导致双链稳定性降低.     

氯化异黄连碱季铵盐的全合成

目的探讨天然产物氯化异黄连碱季铵盐的全合成方法。方法以邻苯二酚为起始原料,经环合、氧化、缩合、还原和闭环5步反应合成天然产物氯化异黄连碱季铵盐。结果路线总收率为20.03%(以邻苯二酚计),其结构经~1H-NMR、~(13)C-NMR和MS谱确证。结论本合成方法原料易得、操作简单、成本较低,适合氯化异黄连碱季铵盐的批量合成,具有潜在的应用价值。     

1α-羟基胆固醇的合成工艺改进

文章对1α-羟基维生素D₃关键中间体1α-羟基胆固醇(1)的合成工艺进行改进：以胆固醇(2)为原料，经过氧化脱氢、环氧化、选择性开环、异构化和还原等5步反应得到1。较现有1的制备工艺，该路线一方面规避了液氨/锂于-78℃还原的苛刻条件，操作简单，条件温和；另一方面采用苯硒酚对1α,2α-环氧-4,6-胆甾二烯-3-酮(4)进行选择性开环，并由I₂/乙酸异丙烯酯体系实现由烯酮异构化为烯醇酯。采用优化后的工艺，1的总收率达40%，纯度为98%。     

SGLT2抑制剂LX4211的合成方法研究

目的研究SGLT2抑制剂LX4211的合成方法。方法以L-(-)-木糖为起始原料,经羟基保护、氧化、酰胺化得到中间体(5S)-1-C-4-吗啉基-4,5-O-异亚丙基-D-2,5-呋喃木糖二醛,该中间体与5-溴-2-氯-4'-甲氧基二苯甲烷缩合,再经还原、脱保护、开环扩环、酯化、溴代、硫醚化、醇解得到目标化合物LX4211。结果与结论优化并确定了LX4211的合成路线,总收率由18.1%提高至23.2%(以L-(-)-木糖计),其结构经1H-NMR和MS确证。该路线成本较低、操作简便、条件温和、收率高,具有工业化生产的潜力。     

多烯紫杉醇的合成工艺研究

目的 改进多烯紫杉醇的合成工艺,寻找一条适合于工业生产的切实可行的合成路线。方法 以顺式肉桂酸乙酯为起始原料,经不对称环氧化、叠氮开环、氢化等反应制备噁唑烷羧酸型侧链;将该侧链与选择性保护的母核结构—10-去乙酰基巴卡亭Ⅲ连接,经酯化、脱保护基反应合成多烯紫杉醇。结果 目标化合物的结构经¹H-NMR、¹³C-NMR、MS、IR、元素分析确证,合成C₁₃位手性侧链的收率为66%,酯化及脱保护反应的收率为60%。结论 新工艺路线采用低成本原料,简单可行、适合于工业化生产。     

抗青光眼药地匹福林的合成工艺改进

目的:改进抗青光眼药地匹福林的合成工艺.方法:以肾上腺素的中间体肾上腺酮为原料,经酰化、催化氢化两步反应合成地匹福林.结果:所得产物结构经红外光谱、核磁共振谱及质谱等确证,总收率为18.1%.结论:该合成路线可行并易于工业生产.     

(R)-(-)-1-(2-萘基)-2-N-甲基氨基乙醇的合成

目的研究拟β-肾上腺素(R)-(-)-1-(2-萘基)-2-N-甲基氨基乙醇(1)的合成方法.方法以β-萘乙烯(2)为原料,通过烯烃的Sharpless不对称双羟化、环化、选择性开环、催化氢化、甲酰化、还原等6步反应制备目标产物.结果与结论设计的合成路线以β-萘乙烯计,6步反应总收率为39.3%,ee值高达97%～99%,合成路线易行.目标产物的结构经质谱、红外光谱、1H-NMR和13C-NMR确证.     

G-quadruplex based probes for visual detection and sensing

Recent advances in colorimetric biosensing have led to rapid methods for target detection, potentially leading to applications on-site, at the point-of-need. This review focuses on one such platform, the G-quadruplex-hemin based DNAzymes, which exhibit peroxidase- like activity. Since their discovery in the late 1990s, various approaches have been adopted in applying the unique catalytic properties of these DNAzymes to detecting nucleic acids, proteins, metal ions and other ligands, through the oxidation of substrate pre-cursors into colored products. G-quadruplex based DNAzymes act as modular units of G-rich DNA sequences, and hence can be synthesized cheaply and conveniently using routine oligonucleotide synthesis. Herein, we discuss the various strategies that have been developed to exploit this class of DNAzymes as candidate probes for optical detection and sensing, for a variety of chemical and biological targets.     

Albumin nanoparticles as carriers for a phosphodiester oligonucleotide

The goal of this study was the evaluation of albumin nanoparticles as drug delivery systems for antisense oligonucleotides. Bovine serum albumin (BSA) nanoparticles were prepared by a coacervation process. A phosphodiester oligonucleotide was either incorporated into the matrix of the particles by incubation with the albumin prior the coacervation process or adsorbed onto the pre-formed nanoparticles. Incorporated and/or adsorbed oligonucleotide was estimated by capillary electrophoresis and fluorescence spectroscopy. The adsorbed amount of oligonucleotide was dramatically dependent on the pH of the medium. Desorption of the oligonucleotide was also affected by the pH and ionic strength of the medium. This indicated that electrostatic forces play a major role in the interaction between the oligonucleotide and the nanoparticles. When the oligonucleotide was incubated with the albumin prior to nanoparticle formation, the profile of release confirmed that a fraction was incorporated into the matrix and its release was controlled by the albumin degradation. The hybridisation capability of the oligonucleotide in both nanoparticle formulations was retained. However, only the oligonucleotide incorporated into the nanoparticle matrix was protected against enzymatic degradation.     

Synthesis and biological activity of 6-substituted-2-oxo-purine nucleosides

We have synthesized various 6-substituted-2-oxo-purine nucleosides from key intermediate, 6-[(4-methylphenylthio)-2-oxo-9-(2,3,5-tri-o-acetyl-β-D-ribofuranosyl)]-2,3-dihydropurine in relatively high yields by one step nucleophilic substitution. Various isoguanosine, xanthosine analogs and other 2-oxo-purine nucleosides containing nitrogen, sulfur and oxygen at C-6 of purine base were easily obtained by this method. The structures of the products were established on the basis of their spectral data studies. And cytotoxicity of resulting synthetic 6-substituted-2-oxo-purine nucleosides against some tumor cell-lines was examined. ED₅₀ values of these synthetic compounds were above 100 μg/ml except isoguanosine, N⁶-methyl isoguanosine and thioxanthosine analogs.     

Role of a non-natural beta-C-nucleotide unit in DNA as a template for DNA and RNA syntheses and as a substrate for nucleolytic digestion.

A non-natural beta-C-nucleoside bearing a 3,4-dibenzyloxyphenyl group as a nucleobase (X) was synthesized and incorporated into a 34-mer oligomer with the sequence 5'-dTTTTTAAAAAAXATATAGCAGCGACATGTCACCG-3'. This synthetic oligonucleotide was examined for template activity in the enzymatic syntheses of DNA by the Klenow fragments of Escherichia coli DNA polymerase I and the recombinant DNA polymerase I, and in the synthesis of RNA by the E. coli RNA polymerase core enzyme. As a result, the template-directed polymerization of both DNA and RNA was precisely terminated at the position of X. The X-containing oligonucleotide was also tested for digestion by an exonuclease, Exo III nuclease (Exo III), and an endonuclease, Mung Bean nuclease (MB). The results indicate that the artificial nucleobase X acts as a terminator for digestion by Exo III, whereas the site X becomes susceptible to digestion by MB. These findings provide a useful tool for the size control of products in the synthesis and degradation of nucleic acids.     

Site specific synthesis and polymerase bypass of oligonucleotides containing a 6-hydroxy-3,5,6,7-tetrahydro-9H-imidazo[1,2-a]purin-9-one base, an intermediate in the formation of 1,N2-etheno-2'-deoxyguanosine

The reaction of DNA with certain bis-electrophiles such as chlorooxirane and chloroacetaldehyde produces etheno adducts. These lesions are highly miscoding, and some of the chemical agents that produce them have been shown to be carcinogenic in laboratory animals and in humans. An intermediate in the formation of 1,N2-ethenoguanine is 6-hydroxy-3,5,6,7-tetrahydro-9H-imidazo[1,2-a]purin-9-one (6-hydroxyethanoguanine), which undergoes conversion to the etheno adduct. The chemical properties and miscoding potential of the hydroxyethano adduct have not been previously studied. A synthesis of the hydroxyethano-adducted nucleoside was developed, and it was site specifically incorporated into oligonucleotides. This adduct had a half-life of between 24 and 48 h at neutral pH and 25 degrees C at the nucleoside and oligonucleotide levels. The miscoding potential of the hydroxyethano adduct was examined by primer extension reactions with the DNA polymerases Dpo4 and pol T7-, and the results were compared to the corresponding etheno-adducted oligonucleotide. Dpo4 preferentially incorporated dATP opposite the hydroxyethano adduct and dGTP opposite the etheno adduct; pol T7- preferentially incorporated dATP opposite the etheno adduct while dGTP and dATP were incorporated opposite the hydroxyethano adduct with nearly equal catalytic efficiencies. Collectively, these results indicate that the hydroxyethano adduct has a sufficient lifetime and miscoding properties to contribute to the mutagenic spectrum of chlorooxirane and related genotoxic species.     

Evaluation of synthetic oligonucleotides as inhibitors of West Nile virus replication

A series of synthetic oligonucleotide phosphorothioate 15-mers were generated against specific sequences in the West Nile virus RNA genome. These antisense oligonucleotides targeted (1) conserved features of the West Nile virus RNA genome that may be expected to lead to inhibition of virus replication since such features play essential roles in the virus lifecycle; (2) G-quartet oligonucleotides with potential facilitated uptake properties and that also targeted conserved sequences among a range of West Nile virus strains. Several formulations with significant in vitro antiviral activity were found. Among the active oligonucleotides were examples that targeted both C-rich RNA sequences of the West Nile RNA genome as well as recognized conserved sequences key to West Nile virus replication. Since the antiviral activity of the latter oligonucleotides diminished upon 2'-O-methyl substitution, it is likely that their activity involves RNase H-catalyzed RNA degradation. One G-rich oligonucleotide that did not target a West Nile virus RNA sequence also was found. These results suggest the potential of antisense strategies for the control of West Nile virus replication if the attendant problem of oligonucleotide delivery can be adequately addressed.     

Targeted delivery of a splice-switching oligonucleotide by cationic polyplexes of RGD-oligonucleotide conjugate

Nanoparticle-based delivery has become an important strategy to advance therapeutic oligonucleotides into clinical reality. Delivery by nanocarriers can enhance access of oligonucleotides to their pharmacological targets within cells; preferably, targeting ligands are incorporated into nanoparticles for targeting oligonucleotides to disease sites, often by conjugation to delivery carriers. In this study, a splice-switching oligonucleotide (SSO) was conjugated to a bivalent RGD peptide, and then, the RGD-SSO conjugate was formulated into polyplexes with a cationic polymer polyethylenimine. The resultant polyplexes of RGD-oligonucleotide conjugate demonstrated dramatic increase in the pharmacological response of splicing correction compared to free RGD-SSO conjugate or the polyplexes of unconjugated SSO, through integrin-mediated endocytosis and rapid endosomal release. This study has shown that coupling a targeting ligand to cargo oligonucleotide can maintain the integrin targeting ability after the peptide-oligonucleotide conjugate is complexed with cationic polymer. Preliminary study also revealed that integrin targeting redirects intracellular trafficking of the polyplexes to caveolar pathway and thereby generates greater effectiveness of the oligonucleotide. This study provides a new platform technology to construct multifunctional delivery systems of therapeutic oligonucleotides.     

Isolation of isoguanosine fromCroton tiglium and its antitumor activity

This paper describes the isolation of isoguanosine from Croton tiglium L. and its cytotoxic effect against several tumor cell lines in culture and newly reports that isoguanosine has an antitumor activity against implanted S-180 ascitic tumor mice. Isoguanosine is effective at the dose of 24 mg/kg/day x 5, with T/C value of 168%. Isoguanosine inhibits the growth of S-180 and Ehrlich solid tumor in mice at the optimal doses of 96 mg/kg/day x 12 and 48 mg/kg/day x 12, with 1-T/C values of 65% and 60%, respectively.     

Recent developments in the chemistry and biology of G-quadruplexes with reference to the DNA groove binders

DNA is the chemotherapeutic target for treating diseases of genetic origin. Besides well-known double-helical structures (A, B, Z, parallel stranded-DNA etc.), DNA is capable of forming several multi-stranded structures (triplex, tetraplex, i-motif etc.) which have unique biological significance. The G-rich 3'-ends of chromosomes, called telomeres, are synthesized by telomerase, a ribonucleoprotein, and over-expression of telomerase is associated with cancer. The activity of telomerase is suppressed if the G-rich region is folded into the four stranded structures, called G-quadruplexes (G4-DNAs) using small synthetic ligands. Thus design and synthesis of new G4- DNA ligands is an attractive strategy to combat cancer. G4-DNA forming sequences are also prevalent in other genomic regions of biological significance including promoter regions of several oncogenes. Effective gene regulation may be achieved by inducing a G4-DNA structure within the G-rich promoter sequences. To date, several G4-DNA stabilizing ligands are known. DNA groove binders interact with the duplex B-DNA through the grooves (major and minor groove) in a sequence-specific manner. Some of the groove binders are known to stabilize the G4-DNA. However, this is a relatively under explored field of research. In this review, we focus on the recent advances in the understanding of the G4-DNA structures, particularly made from the human telomeric DNA stretches. We summarize the results of various investigations of the interaction of various organic ligands with the G4-DNA while highlighting the importance of groove binder-G4-DNA interactions.