Synthesis of 4′-Trifluoromethyl Nucleoside Analogs

Abstract

A strategy based on the use of (trifluoromethyl) trimethylsilane for introduction of the trifluoromethyl group at the C-4 of ribose has been developed and utilized in the synthesis of various novel 4′-trifluoromethylated nucleoside analogs. Screening of these analogs against HIV did not reveal significant biological activity.     

DSC — A Valuable Tool in Heterocyclic Synthesis

Many decomposition and ring closure reactions in the azide series (e.g. a cyclization and rearrangement reaction sequence from the azido ester 1 via the ethoxy oxazole 2 to the oxazolone 3), intramolecular rearrangement reactions (e.g. via a-oxoketenes), self condensation of p-octopamine and also reactions with two reactants and the influence of solvents at the reaction conditions were studied using DSC (Differential Scanning Calorimetry).     

Fluorinated Analogs of the Carotenoprotein, α-Crustacyanin

Four analogs of the carotenoprotein α-crustacyanin have been prepared by reconstitution with the all-transisomer of four new carotenoids (10-F, 10,10′-F₂and 14-F-astaxanthins, and 10′-F-adonirubin). All four blue carotenoproteins exhibit absorption spectra similar to that of the natural α-crustacyanin with λ_maxin the range of 613–625 nm. Different rates of pigment formation and yields were noted. F NMR spectra of pigments derived from the three 10F carotenoids have been recorded. Fourcisisomers of 14-F-astaxanthin and one of 10′-F-adonirubin were also isolated.     

Syntheses of α and γ-BHC Alkylthio Analogs

Meso-(1245/36)-1,2,4,5,6-pentachloro-3-methylthiocyclohexane, and (124/356)-1,2,4,5,6-pentachloro-3-methylthio and ethylthiocyclohexanes were prepared from (1234/56)-1,4,5,6-tetrachloro-2,3-epoxycyclohexane (α-BTC cis-epoxide).     

Interaction between DNA Polymerase λ and Anticancer Nucleoside Analogs

The anticancer activity of cytarabine (AraC) and gemcitabine (dFdC) is thought to result from chain termination after incorporation into DNA. To investigate their incorporation into DNA at atomic level resolution, we present crystal structures of human DNA polymerase λ (Pol λ) bound to gapped DNA and containing either AraC or dFdC paired opposite template dG. These structures reveal that AraC and dFdC can bind within the nascent base pair binding pocket of Pol λ. Although the conformation of the ribose of AraCTP is similar to that of normal dCTP, the conformation of dFdCTP is significantly different. Consistent with these structures, Pol λ efficiently incorporates AraCTP but not dFdCTP. The data are consistent with the possibility that Pol λ could modulate the cytotoxic effect of AraC.     

Synthesis of Analogs of Optically Active α-Ionylideneacetic Acid

The Wittig reaction of (?)-α-ionone (VIa) with carbethoxymethylenetriphenylphosphorane afforded (?)-ethyl α-ionylideneacetate (VIIa). tert-Butyl chromate oxidation of the above ester (VIIa) gave (?)-ethyl 4′-keto-α-ionylideneacetate (VIlla). Selenium dioxide oxidation of (?)-α-ionone (IVa) in ethanol afforded (?)-1′-hydroxy-α-ionone (X), which reacted with car-bethoxymethylenetriphenylphosphorane to give (?)-ethyl 1′-hydroxy-α-ionylideneacetate (XI). tert-Butyl chromate oxidation of the hydroxy-ester (XI) gave (?)-ethyl abscisate (XII) and ethyl 3′-keto-β-ionylideneacetate (XIII). The sensitized photooxidation of ethyl dehydro-β-ionylideneacetate (XVI) using chlorophyll was attempted.     

Absolute Stereochemistry of Analogs of Optical Active α-Ionylideneacetic Acids

Two kinds of iron-containing proteins the molecular masses of which were about 10 kDa and 24 kDa were isolated from cytoplasmic fractions of Mycobacterium smegmatis grown under iron-sufficient (50 μM Fe) and iron-overload (500 μM Fe) conditions. Based upon the elution profiles in two chromatographic systems, spectrophotometric analysis, and ESR spectrum measurement, the protein of 10 kDa met the criteria for classification as a ferredoxin. Another protein of 24 kDa showed no enzymatic activity, though its detailed structure was unknown. The ferredoxin and the protein of 24 kDa contained about 30% and 50% of the total cellular iron, respectively, when cells were grown under the above conditions. The synthesis of the protein of 24 kDa was, however, completely repressed in cells grown under iron-deficient (0.5 μM Fe) conditions, although the ferredoxin was still synthesized to some extent even in iron-deficient cells. These results suggested that both ferredoxin and the protein of 24 kDa could be synergistically involved in iron storage in this organism.     

Synthesis of N-Aminopyrazinium Analogs of Cytidine and 2′-Deoxycytidine

Abstract

N-Aminopyrazine analogues of cytidine and 2′-deoxycytidine were prepared from 1-(β-D-ribofuranosyl)-1,2-dihydro-2-oxopyrazine and 1-(2-deoxy-β-D-ribofuranosyl)-1,2-dihydro-2-oxopyrazine, respectively, by amination with O-mesitylenesulfonylhydroxylamine.     

Molecular Interactions between (?)-Epigallocatechin Gallate Analogs and Pancreatic Lipase

The molecular interactions between pancreatic lipase (PL) and four tea polyphenols (EGCG analogs), like (−)-epigallocatechin gallate (EGCG), (−)-gallocatechin gallate (GCG), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin (EC), were studied from PL activity, conformation, kinetics and thermodynamics. It was observed that EGCG analogs inhibited PL activity, and their inhibitory rates decreased by the order of EGCG>GCG>ECG>EC. PL activity at first decreased rapidly and then slowly with the increase of EGCG analogs concentrations. α-Helix content of PL secondary structure decreased dependent on EGCG analogs concentration by the order of EGCG>GCG>ECG>EC. EGCG, ECG, and EC could quench PL fluorescence both dynamically and statically, while GCG only quenched statically. EGCG analogs would induce PL self-assembly into complexes and the hydrodynamic radii of the complexes possessed a close relationship with the inhibitory rates. Kinetics analysis showed that EGCG analogs non-competitively inhibited PL activity and did not bind to PL catalytic site. DSC measurement revealed that EGCG analogs decreased the transition midpoint temperature of PL enzyme, suggesting that these compounds reduced PL enzyme thermostability. In vitro renaturation through urea solution indicated that interactions between PL and EGCG analogs were weak and non-covalent.     

Synthesis and Evaluation of 2′-Deoxy-2′-Spirodiflurocyclopropyl Nucleoside Analogs

The preparation of 2′-deoxy-2′-siprodifluorocyclopropany-lnucleoside analogs has been achieved from α-d-glucose in several steps. The key step in the synthesis was the introduction of the difluorocyclopropane through a difluorocarbene type reaction at the 2′-position. Then, a series of novel 2′-deoxy-2′-spirodifluorocyclopropanyl nucleoside analogs were synthesized using the Vorbrüggen method. All the synthesized nucleosides were characterized and subsequently evaluated against hepatitis C and influenza A virus strains in vitro.     

Effects of 3-Methylgibberellin Analogs on Gibberellin 3β-Hydroxylases and Plant Growth

Six 3-methylgibberellin analogs were synthesized, and their effects on the GA 3β-hydroxylases from immature seeds of Phaseolus vulgaris and Cucurbita maxima, and/or on the growth of dwarf rice (Oryza sativa L. cv. Tan-ginbozu) and cucumber (Cucumis sativus L. cv. Spacemaster) were investigated. 3-Methyl-GA₅ and 2, 3-didehydro-3-methyl-GA₉· inhibited the conversion of [2, 3-³H2]GA₉ to [2-³H]GA₄ by GA 3β-hydroxylases from both P. vulgaris and C. maxima at 3 μM and higher. Their C/D-ring-rearranged isomers, 2, 3-didehydro-3-methyl-DGC and 16-deoxo-2, 3-didehydro-3-methyl-DGC, inhibited 3β-hydroxylation by the enzyme from P. vulgaris threefold more strongly than the non-C/D-ring-rearranged compounds, but exhibited no effect on 3β-hydroxylation by the enzyme from C. maxima. In a dwarf rice seedling assay, 3-methyl-GA₅ and 2, 3-didehydro-3-methyl-GA₉ promoted shoot elongation at doses of 300 ng/plant and higher, and 3α-methyl-GA₁ and 3α-methyl-GA₄ at doses of 30 ng/plant and higher. In contrast 2, 3-didehydro-3-methyl-DGC inhibited shoot growth to half that of the control at a dose of 300 ng/plant, and 16-deoxo-2, 3-didehydro-3-methyl-DGC showed no effect on growth. In a cucumber seedling assay, 3α-methyl-GA₄ promoted hypocotyl elongation at doses of 300 ng/plant and higher. The other C-3 methyl compounds showed no effect on the hypocotyl elongation of cucumber seedlings.     

2-Fluoro and 2-Methoxycarbonyl Epoxy-β-ionylideneacetic Acids as Abscisic Acid Analogs

Abscisic acid (ABA) is easily isomerized to inactive trans-ABA by light. To solve this problem, two variations of epoxy-?-ionylideneacetic acid were synthesized as ABA analogs, each of them having a methoxycarbonyl or a fluoric substituent at the 2-position. The 2E-, and 2Z-fluorinated analogs showed moderate growth inhibitory activity toward rice seedlings and lettuce seeds, whereas the methoxycarbonyl analog was inactive toward rice seedling growth and only partially active toward lettuce germination. The 2E-fluorinated analog was extensively isomerized to the 2Z-isomer by UV irradiation. We think that a steric requisite for the 2E-position was high, and that the fluorine substituent was not effective for fixing the 2-double bond in the E-configuration.     

Antiviral Activities of β-Enantiomers of 3′-Substituted-3′-deoxythymidine Analogs

Abstract

Several β-L-3′-substituted-3′-deoxythymidine were stereospecifically synthesized. None of these analogs inhibited HIV-1 nor HBV replication in vitro suggesting that these β-L-pyrimidine derivatives may not be efficiently phosphorylated inside the cells.     

Excision of β-L- and β-D-Nucleotide Analogs From DNA by p53 Protein

Abstract

The tumor suppressor p₅₃ protein plays a critical role in the cell-cycle progression. The role of the 3′-to-5′ exonuclease activity of p53 protein in the DNA repair process remains elusive. Using an in vitro exonuclease assay and defined oligonucleotides terminated with β-D- and β-L-nucleoside analogs at the 3′-terminus, we studied the ability of p53 protein to excise β-L- and β-D-nucleoside analogs which have anticancer or antiviral potential. p53 protein removes β-D-nucleoside analogs more efficiently compared to that of β-L-nucleoside analogs. The affinity of p53 protein for an β-L-nucleotide terminated primer was 5 fold lower compared to non-modified primer. The hypothesis on an important role of the 3′-to-5′ exonuclease activity of p53 protein in the action of nucleoside analogs was proposed.     

Structural—Functional Relationships between Terminal Deoxynucleotidyltransferase and 5′-Triphosphates of Nucleoside Analogs

Substrate properties of nucleoside 5′-triphosphate (NTP) analogs, namely, 5′-triphosphates of L- and D-arabinonucleosides (D-FIAUTP, D-FMAUTP, and L-FMAUTP), D- and L-enantiomers of ddCTP analogs (D-ddCTP, L-ddCTP, D-FOddCTP, L-OddCTP, and L-SddCTP), and acyclic guanosine analogs (acyclovir and penciclovir) towards terminal deoxynucleotidyltransferase (TdT, EC 2.7.7.31) were studied. TdT can polymerize 5′-triphosphates of arabinonucleoside analogs (D-FIAUTP and D-FMAUTP). In contrast, L-FMAUTP is not recognized by TdT as a substrate. Kinetic parameters of D- and L-enantiomers of ddCTP analogs and 5′-triphosphates of acyclic nucleosides were evaluated. It is shown that stereospecificity of dNTP analogs and structure of the furanose residue play crucial roles in the interaction with TdT: L-enantiomers are much less potent as substrates compared to their D-counterparts. 5′-Triphosphates of acyclovir (ACVTP) and penciclovir (PCVTP) are about two orders of magnitude less effective as substrates than nucleosides bearing furanose residues, with PCVTP being a better substrate than ACVTP. It can be assumed that the hydroxyl group of PCVTP mimics the 3′-hydroxyl group of the ribose residue and plays an important role in the interaction with TdT.__________Translated from Biokhimiya, Vol. 70, No. 8, 2005, pp. 1078–1085.Original Russian Text Copyright © 2005 by Kukhanova, Ivanov, Jasko.     

2′,3′-Dideoxyadenosine Analogs of the Nucleoside Antibiotics Tubercidin,Toyocamycin and Sangivamycin

Abstract

Application of previously described methodologies, for the synthesis of 2′,3′-dideoxy-2′,3′-didehydro nucleosides from the parent ribonucleosides, to the antibiotics tubercidin (1), toyocamycin (6) and sangivamycin (10) has provided the corresponding 2′,3′-unsaturated nucleosides 4, 9, and 13. A reduction of the 2′,3′-unsaturated moiety has afforded the 2′,3′-dideoxynucleoside antibiotics 5, 14, and 15.     

Octapeptide Analogs of Somatostatin Containing α,α-Dialkylated Amino Acids with Potent Anticancer Activity

We describe the synthesis and anticancer activities of octapeptide analogs of somatostatin incorporating α,α-dialkylated amino acids. The designed analogs of somatostatin are: d-Phe¹-Cys²-Tyr³-d-Trp⁴-Orn⁵-Xxx⁶-Pen⁷-Thr⁸-NH₂ where Xxx=α-Aminoisobutyric acid (Aib), Diethyl glycine (Deg), 1-Aminocyclopentane carboxylic acid (Ac5c), and, d-Phe¹-Cys²-Tyr³-d-Trp⁴-Lys⁵-Ac5c⁶-Pen⁷-Thr⁸-NH₂ (disulphide bond between Cys² and Pen⁷ in all analogs). The conformational studies two of the designed analogs were carried out by NMR techniques and the experimental results suggest a β-turn structure for one of the designed analog. In vivo tumor regression study of two designed analogs on human primary colon tumor xenografts in nude mice demonstrates the anticancer potential of the synthesized analogs.     

Synthesis of 2′-Substituted Inosine Analogs via Unusual Masking of the 6-Hydroxyl Group

2′-Modified inosine analogs have been synthesized from 6-chloropurine riboside via 6-dimethylaminopurine or 6-benzyloxypurine intermediates. The dimethylaminopurine intermediate was obtained via an unusually facile dimethylamine transfer from dimethylformamide.

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