Study On Novel Nucleoside Analogues With Carbohydrate Fragment Modified

Nucleoside analogues have been widely used in the clinical treatment for their effectively antiviral and antitumour abilities. With the development of synthetic technology and pharmaceutical research method, a good deal of new nucleosides are prepared for antiviral infection and antitumour research in recent years, such as telbivudine (L-dt) was approved to be used in HBV treatment by FDA in 2006. However, the existing drugs can't treat thoroughly malignancy and some viral infection disease with high incidence, such as HBV. Moreover, the problem of drug tolerance is increasing in clinical treatment. Which are counterworking the application and developmentof this series of compounds. Therefore, peoples study are focus on looking for novel nucleoside analogues with high efficiency and low toxicity.The antiviral and antitumour mechanism of nucleoside drugs is that these compounds have the similar chemical structure with the natural nucleosides, and could be introduced into the DNA chain of host cell to inhibit viral and tumour cell by interfering the synthsis of its DNA and protein. The modification on nucleosides were base and carbohydrate fragments, most of these compumds were that with carbohydrate fragment modified. The categories of modifaction included acyclicnucleosides, deoxyribonucleoside, the introduction of heteroatoms, configure inversion and enlargement or minish of carbohydrate ring.1. The design of target compoundBy the analysis of the relevant research reports, it is found that many acyclicnucleosides possess antiviral activity, introduction of heteroatom into the carbohydrate fragments of nucleosides can change the bioactivity, selenium exerts anticancer and antiviral activities by affecting the enzyme in organisms, many L-nucleoside analogues have better antiviral activity and lower cytotoxicity than their D-isomers. Therefore, on the basis of analyzing the structure and activity of existing nucleoside analogues, novel fluorinated (azido-) seconucleoside analogues, seleno nucloside analogues and L- nucloside analogues are in the light of the target compounds of this paper. The synthetic method and bio-activity study on these title compounds, would provide use for reference for related study in this field for the future.2. The synthesis of target compoundsThe synthesis route of all these target compounds were disigned with retrosynthetic analysis, the method of natural nucleosides modified on carbohydrate fragment were adopted.2.1 The preparation of fluorinated (azido-) seconucleosides.Starting from four natural ribonucleoside (adenosine, cytosine, guanine, thymine), the amino groups were protected selectively, and the 5'-hydroxy was following protected selectively. Then the pre-activated nucleotide sulfonic ester with an opened ring was obtained after oxido-reduction and sulfonylation. The pre-activated mesylate reacted with NaN3 and subsequent deprotection on amindo and 5'-hydroxy, giving for kinds of 2', 3'- diazide seconucleosides. The poor yield while NaN3 used as nucleophile was solved by moisture control of reacting system.The dimesylate of purine seco-nucleosides reacted with TBFA and subsequent deprotection giving 2', 3'-difluorinated seconucleosides. After the 3-N was protected with PMB, the uridine was oxidatied, reducted, activated and fluorated, and which giving 2', 3'-difluo seco cytosine analogues by 4-carbonyl activation,aminolysis and deprotection. This process provide a way to synthsize 2', 3'-difluo seco pyrimidine analogues which can't be prepared by fluorination directly.Controlling the reaction conditions and the ratio of reactants in the azide nucleophilic substitution reaction of purine seconucleotide dimesylate can produce intermediates with azide substituent only at position 3'position, followed by fluorination nucleophilic substitution reaction at position 2'and deprotection, yielding 2'-fluo,3'-azide-2', purine seconucleoside analogues.Controlling the reaction conditions and the ratio of reactants in the fluorination nucleophilic substitution reaction of seconucleotide dimesylate give intermediates with fluorinatd substituent only at position 3'position, followed by azide nucleophilic substitution at position 2'and deprotection, yielding 2'-azido, 3'-fluo- purine seconucleoside analogues. The seco-uridine dimesylate experienced an intramolecular cyclisation, forming a 2, 2'-anhydrous intermediate. After fluorination at oposition 3', the ring was opened by reacting with NaN3. 2'-Azido, 3'-fluo uridine analogue was obtained by deprotection. The correspoding cytosine analogue were obtained through activation and aminolysis of the protective uridine analogue. Selective fluorination process was established.2.2 The preparation of seleno nucleoside analoguesNaHse aqueous solution, was used as seleniferous nucleophile, reacting with dimesylate of the four seconucleosides in dioxane-water solution, then deprotecting to give novel nucleoside analogues with 1, 4- oxaselenine ring as carbohydrate fragment. Compared with the preparation of other 1,4-oxaselenine ring structure in the literature, better yield and more convenient separation were achieved in this step.2.3 The preparation of L-nucleoside analogues with six-membered ring as carbohydrate fragment.L-nucleoside was prepared from L-ribose by five steps. After protection selectively, oxidation-reduction and mesylation, L-uridine and 5-methyl-L-uridine respectively with sodium hydroxide, arduous sodium sulfide and NaHSe, then removed the protective group to give uridine and thymidine nucleoside analogues with 1, 4-dioxane, 1,4-oxathiane, 1,4-oxaselenine ring as carbohydrate fragment. L-cytosine analogues were obtained through activation and aminolysis of 4-carbonyl group from the corresponding L-uridine analogues with protective groups. Although there were much steps in this process, but good yields and convenient seperation were achived for the ripely reacting conditons.There are 108 compounds prepared in this paper, and 58 of them were not reported. Their structures were confirmed by 1H NMR, 13C NMR, H-H COSY, MS, HRMS and X-ray single crystal diffraction.3. The primary activity evaluation The three series of compounds were primary evaluated in vitro for their inhibitory activities on viral and tumour cells. The result showed that the seco-nucleoside analgues have no cytotoxicity in test and some of them showed anti- HSV-I activity. The seleno nucleoside analogues didn't exihibited significant inhibition effect on A549, LOVO, CEM, but there was diversity of the four compounds. L- nucleoside analgues showed no inhibition effect on tumour cells in test. The antiviral test of seco- and L- nucleoside analgues was in preparation.On all accounts, three series of nucleoside analgues with carbohydrate fragment were successfullydesiged and prepared. Meanwhile, Synthetic procedures were studied yielding a facile and efficient methodology by the study of their synthetic process. The result of primary activity evaluation provided investigative idea and reference, supplied the material of study on nucleoside analogues.