Synthesis and evaluation of hexitol nucleoside congeners as ambiguous nucleosides

A series of anhydrohexitol nucleoside congeners was synthesized as ambiguous or so-called universal nucleosides and was evaluated for their hybridization potential and discrimination properties. The 1,5-anhydro-2,3-dideoxy-2-(5-nitroindazol-1-yl)-d-arabino-hexitol 4e showed the lower spread in T_m values upon hybridization to the natural bases, with minimal destabilization, and therefore behaved as a true ambiguous nucleoside.     

Synthesis of 2,5-disubstituted pyrazolyl-1,3,4-oxadiazoles by the Huisgen reaction

Russian Chemical Bulletin - We developed an approach to the synthesis of 2,5-disubstituted pyrazole-containing 1,3,4-oxadiazoles by acylation of 5-(nitropyrazolyl)tetrazoles with alkyl, aryl, and...     

Synthesis of new azido porphyrins and their reactivity in copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction with alkynes

We report herein the preparation of two novel porphyrins substituted with an azido group born either on the para-position of one phenyl meso-susbtituent of a tetraaryl zinc porphyrin (1) or directly on the meso-position of a trisaryl nickel porphyrin (2). We studied the scope and the limitation the Huisgen cycloaddition reaction of these two porphyrins using different catalytic conditions. We observed that the carbene (SIMes)CuBr in THF/H₂O 3:1 at 45 °C for 60 h gives almost quantitative yields for the reaction between 1 and different alkynes, but significantly lower yields with 2 probably due to its thermal instability.     

Synthesis of fullerene glycoconjugates via a copper-catalyzed Huisgen cycloaddition reaction

The synthesis of fullerene-carbohydrate conjugates using a copper-catalyzed [3+2] cycloaddition reaction to facilitate the union of an azido-functionalized sugar and a pentaalkynyl[60]fullerene is straightforward. Thus, fullerenes bearing five oligosaccharides such as Gb3-trisaccharide can be readily accessed. Nanometer-scale molecular architectures presenting as many as 15 sugar moieties in C5-symmetry are readily produced. The cycloaddition reaction proceeds quantitatively under mild conditions without the need to protect the sugar hydroxyl groups.     

Theoretical study of the regioselectivity of the Huisgen reaction

From the structure of a series of spiro (pyrrolidine-2,3′-oxindole) derivatives synthesized by Huisgen reaction of isatin, α-amino acids, and different olefins, different regioselectivities were found. The possible mechanism of the Huisgen reaction of oxindole azomethine ylide and the substituent of olefins was investigated using a B3LYP/6-311G* level of theory, and the results show that the regioselection depends on the energy barrier between the stacking state and the regioisomer. This mechanism can also be applied to the illumination of other Huisgen reactions.     

Pyrrolopyrimidine nucleosides. XIII. Synthesis and chemical reactivity of certain selenopyrrolo[2,3-d]pyrimidine nucleosides

5-Cyano-7-(β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidin-4-selone ( 1 ) has been prepared via a reaction of the appropriate 4-chloro compound with sodium hydrogen selenide. Alkylation of 2 under basic conditions has provided certain 4-substitutedseleno-5-cyano-7-(β-D-ribofuranosyl)-pyrrolo[2,3-d]pyrimidines. 5-Cyano-4-methylseleno-7-(β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine was allowed to react with hydroxylamine and hydrazine. The products obtained and reaction course were compared to those obtained from identical reactions using the corresponding sulfur analog.     

Synthesis, structure, and reactivity of unexpectedly stable spiroepoxy-beta-lactones obtained by epoxidation of 4-alkylidene-2-oxetanones

We describe the first synthesis of spiroepoxy-beta-lactones obtained via epoxidation of ketene dimers. These compounds display unexpected stability that may be due to a double anomeric effect garnered from analysis of bond lengths by X-ray crystallography of one spirocycle in comparison to calculated bond lengths of related structures. These new strained intermediates display interesting reactivity leading to a butenolide, an alpha-hydroxyketone, a triol, an alpha-chloroketone, and an alpha-azidoketone.     

Staudinger–Vilarassa reaction versus Huisgen reaction for the control of surface hydrophobicity and water adhesion

Surface modifications are keys for a great number of applications. In order to perfectly control the surface properties, it is important to control the modification pathways. Two general pathways can be described in order to introduce modification on surfaces: the post‐strategies and the ante‐strategies. In this work, we focus on the comparison between the Huisgen and the Staudinger–Vilarrasa reaction for both post‐surface and ante‐surface modifications. Here, we focused on the possibility to use both two reactions to obtain superhydrophobic and oleophobic properties. This work includes monomer synthesis, surface modifications with alkyl, aryl or perfluoroalkyl chain. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of coumarin-nucleoside conjugates via Huisgen 1,3-dipolar cycloaddition

An efficient synthesis of fluorescent coumarin-nucleoside conjugates via Cu(I) catalysed Huisgen 1,3-dipolar cycloaddition is described. Starting from azidonucleosides and coumarin derivatives, products are obtained in good yields. The fluorescent properties of the newly prepared coumarin-nucleoside conjugates are determined.     

Cyclopentene carbocyclic nucleosides related to the antitumor nucleoside clitocine and their conversion to 8-Aza-neplanocin analogues. Synthesis and antiviral activity

Synthesis of the cyclopentene carbocyclic analogue of the naturally occurring nucleoside clitocine ( 1 ) is reported. Starting with racemic cyclopentenylamine ( 10 ), the heterocyclic moieties of the clitocine analogue 4 and related 1,6-dihydro-6-oxo, 5 , and 2-amino-1,6-dihydro-6-oxo, 6 , analogues were constructed. These compounds were respectively converted to 8-aza-neplanocin A (7) , 8-aza-neplanocin D ( 8 , the inosine analogue), and the corresponding 8-aza-guanosine analogue 9 after reduction of the nitro group followed by nitrous acid cyclization. Extensive antiviral evaluation revealed that only 8-aza-neplanocin A ( 7 ) had enough antiviral activity to warrant further studies. This compound showed weak antiviral activity against HSV-1, HSV-20 and the thymidine kinase deficient (TK-) HSV-1. However, it displayed good antiviral activity against human cytomegalovirus (HCMV) at a concentration of 0.40–2.50 μg/ml, well below the cytotoxicity threshold. This activity profile is consistent with a mechanism of action involving the inhibition of the enzyme adenosylhomo-cysteine hydrolase.     

Facile access to pyrazolines via domino reaction of the Huisgen zwitterions with aziridines

A novel, efficient, and general domino reaction of 2-acylaziridines with the Huisgen zwitterions to furnish 2-pyrazoline rings is described. A possible mechanism for the domino sequence is proposed.     

Synthesis of a transition state analogue inhibitor of purine nucleoside phosphorylase via the Mannich reaction

[reaction: see text] The expeditious convergent synthesis of the potent human purine nucleoside phosphorylase inhibitor DADMe-Immucillin-G (3) was achieved via the Mannich reaction. The Mannich chemistry of a series of deazapurines and amine hydrochlorides was also investigated.     

Uncharacteristic thione behavior in a Huisgen cycloaddition reaction: a kinetic and theoretical study

In the reaction of phthalazinium-2-dicyanomethanide with adamantanethione the rare ring system [1,3]thiazolo[2,3-a]phthalazine was obtained. An X-ray crystal structure of the product shows regioselectivity with the thione carbon bonded to the dicyanomethanide terminus of the 1,3-dipole. UV kinetic measurements and DFT calculations showed that the rate of cycloaddition of adamantanethione was significantly slower than that of DMAD and no super-dipolarophile character was exhibited. This arose from exceptional lowering of the HOMO energy of the 1,3-dipole by the cyano substituents.     

Synthesis of novel C6-phosphonated purine nucleosides under microwave irradiation by SNAr-Arbuzov reaction

Novel C6-phosphonated purine nucleosides were obtained in good to excellent isolated yields by the simple and catalyst-free SNAr-Arbuzov reaction of trialkyl phosphite with 6-choloropurine nucleosides, including a series of nonsugar carbon nucleosides. Shorter reaction times were needed, and substantially higher yields were obtained under microwave irradiation conditions compared with conventional heating conditions.     

Synthesis of the ezomycin nucleoside disaccharide

[equation--see text] A protected ezomycin octosyl nucleoside was glycosylated at O-6' with a protected ezoaminuroic acid donor to afford, following several functional group modifications, the title compound 1 ( identical with 4-desamino-4-oxoezomycin A(2)).