Total synthesis of N-malayamycin A and related bicyclic purine and pyrimidine nucleosides

Methods are described for the total synthesis of bicyclic perhydrofuropyran nucleosides as N-analogues of the naturally occurring malayamycin A. Formation of the N-nucleosides relied on the activation of thioglycosides, proceeding via sulfonium intermediates. Ring closure metathesis was used in two approaches to build the bicyclic dioxa heterocycle. Another approach relied on the use of a sugar precursor and cyclization to the bicyclic thioglycoside.     

Ferrocene-modified pyrimidine nucleosides: synthesis, structure and electrochemistry

This paper reports syntheses, crystal structures and electrochemical results for two ferrocene(Fc)-modified pyrimidine nucleosides that could potentially be used for investigating electron transfer in DNA. Fc was directly attached to the 5-position of deoxyuridine and deoxycytidine via the Stille coupling reaction. Fc-modified uridine was incorporated into DNA trinucleotides with standard solid-phase synthesis. The structures of corresponding detritylated compounds were determined by single-crystal X-ray analysis. Electrochemical investigations of all compounds by cyclic voltammetry revealed reversible redox processes.     

Analogs of the pyrimidine nucleosides

The kinetics of the hydrolysis of the pseudoglycosidic C-N bond in the N¹-derivatives of uracil, thymine, and 5-fluorouracil at various pH values of the medium have been studied. The dependence of the rate of hydrolysis of N¹-(tetrahydrofuran 2-yl)-5-fluorouracil on the temperature has been investigated. The influence of substituants at C₅ and N₁ of the pyrimidine ring on the stability of the pseudoglycosidic C-N bond has been evaluated.For part V, see [10].     

An efficient synthesis of novel deoxy phospha sugar pyrimidine nucleosides

An efficient method is described in the synthesis of several novel deoxy phospha sugar pyrimidine nucleosides in racemic form, analogs of normal sugar nucleosides, in high yields by treatment of (±)-2-aminophospholane 1-oxide with several, α-cyano-, -acetyl-, -ethoxycarbonyl-β-ethoxy-N-ethoxycarbonylacrylamides.     

Analogs of pyrimidine nucleosides

The UV absorption spectra of 5-substituted N¹-(tetrahydrofuran-2-yl)- and N¹-(2oxotetrahydrofuran-3-yl)uracils have been studied and their protolysis constants have been determined by the spectrophotometric method. A comparison is given with the spectra and pKa values of the corresponding N¹-methyl derivatives and ribosides and deoxyribosides.For part IV see [11].The work was carried out with analytical samples of compounds obtained by us previously [9–12].     

Enantioselective synthesis of chiral carbocyclic pyrimidine nucleosides via asymmetric cyclopropanation

An efficient method to construct chiral cyclopropyl pyrimidine carbocyclic nucleoside analogues bearing a quaternary center was developed via asymmetric Michael-initiated cyclopropanation. The axis chirality was observed in cyclopropyl pyrimidine carbocyclic nucleoside analogues for the first time, which was caused by the rotationally restricted NC bond in N-COPh moiety. Using (DHQD)₂AQN as the organocatalyst, diverse cyclopropyl pyrimidine carbocyclic nucleoside analogues were generated in 76–93% yields and 73–96% ee.     

Analogs of pyrimidine nucleosides

N₁-(-Tetrahydrofuranyl)- and N₁-(-tetrahydropyranyl)uracils and the corresponding 6-azauracils have been obtained by the condensation of bistrimethylsilyl derivatives of uracils and 6-azauracils with-chlorotetrahydrofuran and-chlorotetrahydropyran. The superiority of the silyl method over the mercury method used previously has been demonstrated.For part III, see [9].     

Analogs of pyrimidine nucleosides

A new method was developed for the synthesis of 1-(2-tetrahydrofuryl) derivatives of uracil, 5-substituted uracils, 6-azauracil, and cytosine by alkylation of 2,4-bis(trimethylsilyl) derivatives of pyrimidine bases with 2-acetoxytetrahydrofuran in the presence of Lewis acids. In contrast to 2-chlorotetrahydrofuran, which is used in a previously described method, 2-acetoxytetrahydrofuran is stable at room temperature and reacts under these conditions with silyl derivatives of uracils in the presence of SnCl₄ to give 1-(2-tetrahydrofuryl) derivatives of pyrimidine bases in 80–85% yields.See [1] for communication X.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedineaii, No. 9, pp. 1258–1259. September, 1977.     

Analogs of pyrimidine nucleosides

A new method for the synthesis ofN₁-(dihydroxyalkyl)uracils by reduction of substituted α- (1-uracilyl)- and γ-[(1-uracilyl)methyl]-γ-butyrolactones with sodium borohydride was found.     

Analogs of pyrimidine nucleosides

α-(1-Cytosinyl)-γ-butyrolactone was obtained by condensation of bis(trimethylsilyl)cytosine with α-bromobutyrolactone. The reduction of α-(1-cytosinyl)-γ-butyrolactone with sodium borohydride gave N₁-(1,4-dihydroxy-2-butyl)cytosine, the acylation of which with benzoyl chloride and subsequent partial hydrolysis gave N₁-(1,4-dihydroxy-2-butyl)-N₄-benzoylcytosine.     

Analogs of pyrimidine nucleosides

The reaction of alkoxy bromides with N₁-(-tetrahydrofuryl) derivatives of pyrimidine bases has given a series of 6-alkoxy-5-bromo-1-(-tetrahydrofuryl)-5, 6-dihydrouracils. The hydrogenation of the 1-(-tetrahydrofuryl) derivatives of uracil and of 5-fluorouracil has been studied. It has been shown that in both cases 1-(-tetrahydrofuryl)-5, 6-dihydrouracil is formed.     

Analogs of pyrimidine nucleosides

A number of N₁-(-butyrolactono) derivatives of 5-substituted uracils have been synthesized by condensing the sodium derivatives of the corresponding bases with -bromobutyrolactone or by the halogenation of N₁-(-butyrolactono)uracil.For part I, see [1].     

A short path synthesis of [13C/15N] multilabeled pyrimidine nucleosides starting from glucopyranose nucleosides

The synthesis of fully [13C/15N] labeled pyrimidine nucleosides has been achieved from 13C-glucose and labeled nucleobases. The reaction scheme leads directly to the protected nucleosides without the need for the inversion of configuration of C-3 of 13C-glucose. This was achieved by an oxitative ring-opening reaction removing the carbon with the wrong configuration.