A novel synthesis of N-acetyl-α-d-fucosamine 1-phosphate and uridine 5"-diphospho-N-acetyl-α-d-fucosamine

In connection with studies on the biosynthesis of capsular polysaccharides from Staphylococcus aureus, a new synthesis of uridine 5"-(2-acetamido-2,6-dideoxy--d-galactopyranosyl diphosphate) (uridine 5"-diphospho-N-acetyl--d-fucosamine) using 2-azido-3,4-di-O-acetyl-2,6-dideoxy--d-galactopyranosyl nitrate as the key intermediate was carried out. The reaction of this product with cesium dibenzyl phosphate smoothly affords the corresponding -glycosyl dibenzyl phosphate, which undergoes anomerization on treatment with BF₃·Et₂O and 2-bromopyridine to give -glycosyl dibenzyl phosphate in high yield. This product was then transformed into 2-amino-3,4-di-O-acetyl-2,6-dideoxy--d-galactopyranosyl phosphate, subsequently converted into 2-acetamido-2,6-dideoxy--d-galactopyranosyl phosphate and the target nucleoside diphosphate sugar.     

The first chemical synthesis of pyrazofurin 5′-triphosphate

As an archetype C-nucleoside, pyrazofurin possesses broad-spectrum antiviral and antitumor activities. However, the presence of the acidic enol in the nucleobase of pyrazofurin poses a huge challenge to the conventional NTP synthetic methods. On the basis of a selective phosphorylation method and the P(V)-N activation strategy, the first chemical synthesis of pyrazofurin 5′-triphosphate (PTP) was accomplished, which will greatly facilitate the investigation on the interactions of viral RNA polymerases and PTP, an important cellular metabolite of pyrazofurin.     

Simple and effective method for the synthesis of 3′,5′-substituted 1-β-D-arabinofuranosyluracil

3,5-Substituted arabinofuranosyluracil is a starting compound in 2-modifications. A convenient and effective method is proposed for the synthesis of 1-(3,5-di-o-trityl--D-arabinofuranosyl)uracil by successive reactions of 2,2-cyclization of uridine, 3,5-tritylation of the 2,2-anhydrouridine, and hydrolytic cleavage of the 2,2-anhydro bond.Institute of Organic Synthesis, Riga LV-1006. Odense Universitet, Kemisk Institut, Odense, Denmark. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 975–977, July, 1996. Original article submitted April 25, 1996.     

Stereoselective synthesis of 5′-hydroxyzearalenone

A first stereoselective total synthesis of 14-memebered β-resorcylic macrolactone 5′-hydroxyzearalenone (1) has been achieved. The key steps are Jocobsen hydrolytic kinetic resolution, Sharpless asymmetric dihydroxylation, Vilsmeier-Haack reaction, Mitsunobu esterification and ring-closing metathesis.     

The synthesis of oligoribonucleotides—VII: The use of ribonucleoside 2′,5′-bisketals and 2′-ketal-3′-esters as synthetic intermediates

A proposed general oligoribonucleotide synthesis, based on four suitably protected derivatives of each nucleoside is outlined. The preparations of UpU, ApA, UpUp and UpUpU, from three of the four suggested types of unit, are described. The products have been shown to contain virtually exclusively 3′ → 5′-phosphodiester linkages.     

Chemical transformations of pyridoxal and pyridoxal 5′-phosphate condensation products with amino acids

The mechanism of chemical transformations of pyridoxal and pyridoxal 5′-phosphate condensation products with amino acids is studied by kinetic measurements. The Schiff bases are shown to be fairly stable in neutral media. In acid media, the Schiff bases are hydrolyzed into the initial components. In alkaline media, cleavage of α-hydrogen from the amino acid fragment and structural rearrangement into the quinoid form followed by hydrolysis of the latter with elimination of pyridoxamine and keto acid take place. The rate constants of the chemical transformations of the Schiff bases are found to depend on the pH of the medium. It is shown for the first time that the phosphate group in the pyridoxal 5′-phosphate fragment catalyzes the α-hydrogen cleavage and strongly accelerates alkaline decomposition of the Schiff bases.     

Asymmetric total synthesis of 5′-epi-paecilomycin-F

The asymmetric total synthesis of one of the stereoisomers of the naturally occurring 14-membered ring macrolide paecilomycin-F (5′-epi) has been reported in this article. The main highlight of the synthetic strategy involves the successful application of a ring closing metathesis (RCM) reaction at a late stage. Asymmetric Keck allylation, Sharpless asymmetric dihydroxylation, and Mitsunobu esterification have also been used successfully for the total synthesis of 5′-epi-paecilomycin-F.     

Incompatibility of acid-labile 2′ and 5′ protecting groups for solid-phase synthesis of oligoribonucleotides

Cleavage of 2−O-tetrahydropyranyl groups from ribonucleoside derivatives used in solid-phase oligoribonucleotide synthesis takes place to an unacceptable extent during treatment with protic acid to remove 5′-O-pixyl groups.     

The synthesis of α-methyl-β-phenylisocysteine and the preparation of substituted thiazolidine-5-carboxylic acids

(A) A new route of α-mercapto-β-amino-α,β-disubtituted carboxylic acids has been presented. By condensing 5-methyl-2-thiothiazolidine-4-one and benzylidene-N,N-bisacetamide, 5-methyl-5-[α-acetylaminobenzyl]-2-thiothiazolidine-4-one was obtained and this was converted through its oxime into the corresponding thiazolidine-2,4-dione. By the action of alkali the thiazolidine ring was cleaved and α-methyl-β-phenylisocysteine and its amide obtained.(B) Substituted thiazolidine-5-carboxylic acids and the corresponding acid amides have been prepared by the condensation of α-methyl-β-phenylisocysteine and its amide with formaldehyde, benzaldehyde, ethyl α-formylcaprilate and ethyl α-formylphenylacetate. The acids obtained show no in vitro biological activity.     

Some new derivatives of Cr(III) with uracil,uridine and 5′-UMP

Some new Cr(III) compounds with uracil, uridine and 5′-UMP were obtained by reaction of the starting complexes cis-[Cr(en)₂Cl₂]Cl and [Cr(NH₃)₅Cl]Cl₂ with the base, nucleoside and nucleotide. The complexes were characterized by their elemental analysis, conductivity, reflectance and IR data. In the case of uracil and uridine compounds, indirect bonding of Cr(III) to the pyrimidine ring seems to occur through the C₄O and NH₃(NH₂) groups of the starting complexes. In the 5′-UMP complex direct bonding is inferred through the phosphate group with additional interactions by hydrogen bonds involving the C₄O group.     

Regioselective synthesis of 1-azinyl-1′-isopropenylferrocenes

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