Oligomerization of 3′-amino-3′-deoxyguanosine-5′-phosphorimidazolidate on a d(CpCpCpCpC) template

Summary 3-Amino-3-deoxyguanosine-5-phosphorimidazolidate (ImpGnh ₂) oligomerizes more rapidly and regiospecifically than related nucleotide derivatives on a d(CpCpCpCpC) template. The greater nucleophilicity of the amino group leads to efficient oligomerization even when the structure of the double-helical complex formed by the template and the substrate is not optimal for reaction. The use of amine-containing analogues should permit us to develop models of potentially prebiotic polymerization reactions that cannot be studied easily using natural nucleotides.     

Effects of 3′-C-Methylation on the Hydrolytic Stability and Hydroxyl pK a Values of Dinucleoside 2′,5′- and 3′,5′-Monophosphates

Abstract

The first-order rate constants for hydrolysis of 3′-C-methyluridylyl(2′,5′)- and -(3′,5′)adenosine and the corresponding native dinucleoside monophosphates (2′,5′- and 3′,5′-UpA) have been determined as a function of hydroxide-ion concentration (0.025 - 7 M) at 25°C. In addition to the effects on the hydrolytic stability of the compounds, the effects of the 3′-C-methyl substitution on the kinetically determined pK _a values for the sugar hydroxyls of the undine moiety are discussed.     

REACTION OF N3-BENZOYL-3′,5′-O-(DI-TERT-BUTYLSILANEDIYL)URIDINE WITH HINDERED ELECTROPHILES: INTERMOLECULAR N3 To 2′-O PROTECTING GROUP TRANSFER

ABSTRACT

The compound N³-benzoyl-3′,5′-O-(di-tert-butylsilanediyl)uridine 2 was alkylated with various alkyl iodides in CH₃CN in the presence of base. Normal 2′-O-alkylated products were obtained with methyl or benzyl iodide. if hindered alkyl iodides with β-branching such as 2-ethylbutyl iodide were used as electrophiles under the same conditions, N³-alkyl-2′-O-benzoyl uridine derivatives were produced. This unexpected transformation is usually dormant with reactive alkylating agents, but expressed with sterically hindered, less reactive electrophiles. This unwanted reaction gives isomeric products whose spectra differ in only subtle ways from target compounds.     

INACTIVATION OF S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE WITH FLUORINATED ANALOGS OF 2′- AND 3′-DEOXY-5′-METHYLTHIOADENOSINE

Fluorinated analogs of 2′- and 3′-deoxy-5′-methylthioadenosine 1–4 caused irreversible inactivation of AdoHcy hydrolase. Based on the ESI-Mass spectra analysis of the inactivated enzyme with the fluorinated analog 1 a mechanism of inactivation is proposed.     

FORMATION OF 2′-DEOXY-2-NITROADENOSINES BY REACTION OF 2′-DEOXYADENOSINES WITH COPPER(II) NITRATE/ACETIC ANHYDRIDE

ABSTRACT

Nitration of 9-substituted [ethyl, (Ac)₂-2′-deoxyribosyl, (Ac)₃-ribosyl] N ⁶-acetyladenine derivatives with Cu(NO₃)₂·3H₂O/Ac₂O was examined. Nitration proceeded at the 2-position, although the yield was low. Removal of the acetyl groups gave 2′-deoxy-2-nitroadenosine derivatives.     

Effect of guanosine 3′:5′-monophosphate on the hydroosmotic activity of adenosine 3′:5′-monophosphate in toad urinary bladder

Guanosine 3′:5′-monophosphate has a slight hydroosmotic effect on toad urinary bladder. Furthermore, this nucleotide strongly inhibits the responses to 3′:5′-adenosine monophosphate and oxytocin. The response to an increase in medium tonicity is not modified by the guanosine nucleotide. A role for guanosine 3′:5′-monophosphate in the regulation of water permeability in toad urinary bladder is proposed.     

Methodology for the Synthesis of Dinucleoside Monophosphates Containing A 2′-Deoxy-3-Isoadenosine Unit: 3-iso-dApT and Tp(3-iso-dA)

Abstract

2′ -Deoxy-3-isoadenylyl(3′-5′)thymidine and thymidylyl-(3′-5′)-2′-deoxy-3-isoadenosine have been synthesized by mild protection/deprotection methodology that circumvents facile N3-Cl′ hydrolytic cleavage of the 2′-deoxy-3-isoadenosine moiety.

     

A Convergent Regiospecific Synthesis of the Lariat-Trinucleotides and A2′p 5′G and A2′p 5′G 3′p 5′C from A O4-2-Nitrophenyl) -Uridine Building Block

Abstract

Total synthesis of title compounds 1_ and 2_ from a common intermediate 7 is reported using the phosphotriester-phosphiteamidite approach. Appropriate NMR evidence has been presented in support of the regiospecific synthesis of target molecules in addition to enzymatic analysis. Present work clearly shows that the NMR evidence is mandatory to establish the isomeric purity of branched RNA molecules; enzymatic or/and electrophoretic analysis alone as tools for confirmation of branched RNA structures can be misleading.     

Synthesis and Properties of Some (2′-5′) Linked Dinucleoside Monophosphates Modified with 3′-Difluoromethylene Groups

Abstract

The title dimers were prepared to investigate conditions required for the synthesis of 3′-difluoromethylene modified oligonucleotides on solid support. As a result a new synthetic cycle was developed that enabled the solid phase synthesis of the modified oligonucleotides.     

Only One 3′-Hydroxyl Group Of ppp 5′A 2′p 5′A 2′p 5′A(2–5A) is Required for Activation of the Mouse 2–5A-Dependent Endonuclease

Abstract

The 3′-hydroxyl groups of each of the adenosines of 2–5A triraer (ppp5′A2′p5′A2′p5′A) were sequentially replaced by hydrogen through a phosphotriester synthetic approach. Biochemical evaluation of these analogs led to the conclusion that only the 3′-hydroxy group of the second adenosine is required for activation of RNase L.     

Resistance Profiles of (+) 2′-Deoxy-3′-oxa-4′-thiocytidine and (-) 2′-Deoxy-3′-oxa-4′-thio-5-fluorocytidine

Abstract

Resistant variants were selected in vitro against two novel nucleoside analogues, (+) dOTC and (-) dOTFC using the HIV-1 molecular clone HXB2D. The variants obtained displayed 6.5-fold and 10-fold resistance to these compounds, respectively. Cloning and sequencing of the RT genes of the selected viruses identified two mutations, M184I for (+) dOTC and M184V for (-) dOTFC. Results with mutated recombinant clones of HXB2D confirmed the importance of these mutations in MT-4 cells. The resistance profiles of clinical samples with wild-type or 3TC-resistant phenotypes were also studied; low to moderate levels of cross-resistance were observed against the novel compounds.     

A Solid-Phase Synthesis of 2′,5′-Linked Oligoadenylates (2-5A)

Abstract

2′,5′-Oligoadenylate 5′-triphosphates (2-5A) as products of 2-5A synthetase and activators of ribonuclease L (RNase L), are mediators in one of the mechanisms of interferon′s antiviral action. Upon activation, RNase L inhibits protein synthesis due to the degradation of RNAs. This activity of 2-5A could possibly find an application in virus or cancer chemotherapy, but two major barriers prevent the use of 2′,5′-linked oligoadenylates as therapeutic agents. The 2-5A is readily degraded by a 2′,5′ phosphodiesterase and as a highly negatively charged molecule, is not readily taken up by cells. One possible solution to this latter limitation might be found in chemical modifications of the 2-5A structure. Many analogues of 2-5A have been already obtained with modified base, ribose or phosphate moieties. While these have provided some important information about the enzyme- activator interactions, the cell permeability problem still remains unsolved. One of the major obstacles in this study is lack of a convenient method of synthesis of 2′,5′ ribonucleotides of widely varying structure.     

Steric Effect of a Bulky Substituent At 5′-Position on the Regioselectivity of 2′ vs. 3′-O-Methylation of N6- Cyclohexyladenosine

Abstract

Steric effect of a trityl or substituted trityl group at 5′-OH of N⁶-cyclohexyladenosine on the regioselective 2′ vs. 3′-O-methylation under phase transfer catalysis conditions was investigated. Compound 4 showed only a modest increase in the selectivity of 2′ over 3′-O-methylation compared to compound 1.     

Affinity labeling of the (Na+ + Mg2+)-ATPase from A choleplasma laidlawii B membranes by the 2′,3′-dialdehyde derivative of adenosine 5′-triphosphate

The (Na⁺ + Mg²⁺)-ATPase of the Acholeplasma laidlawii B plasma membrane was inactivated by the 2′,3′-dialdehyde derivative of ATP (oATP). oATP behaved as a reversible competitive inhibitor of this ATPase and was slowly hydrolyzed by the enzyme. In addition, oATP induced an irreversible inactivation of the enzyme. A 62% inactivation of the enzyme correlated with the binding of 16 moles of oATP per mole of the enzyme. In the presence of 5′-adenylyl imidodiphosphate, a non-hydrolyzable substrate analogue, the stoichiometry was 8 moles oATP per mole of ATPase. By SDS-polyacrylamide gel electrophoresis, [U-¹⁴C]oATP was found to bind covalently to four of the five subunits of the enzyme, but specific labeling was highest for the γ-subunit of the ATPase.     

Chemoenzymatic Synthesis of 3′-Deoxy-3′-(4-Substituted-Triazol-1-YL)-5-Methyluridine

An efficient protocol has been developed for the synthesis of a small library of 3′-deoxy-3′-(4-substituted-triazol-1-yl)-5-methyluridine using Cu(I)-catalyzed Huisgen–Sharpless–Meldal 1,3-dipolar cycloaddition reaction of 3′-azido-3′-deoxy-5-methyluridine with different alkynes under optimized condition in an overall yields of 76%–92%. Here, the azido precursor compound, i.e., 3′-azido-3′-deoxy-5-methyluridine was chemoenzymatically synthesized from D-xylose in good yield. Some of the alkynes used in cycloaddition reaction were synthesized by the reaction of hydroxycoumarins or naphthols with propargyl bromide in acetone using K₂CO₃in excellent yields. All synthesized compounds were unambiguously identified on the basis of their spectral (IR, ¹H-, ¹³C NMR spectra, and high-resolution mass spectra) data analysis.     

Oligomerization reactions of ribonucleotides: The reaction of the 5′-phosphorimidazolide of nucleosides on montmorillonite and other minerals

The reaction of ImpA in the presence of Na⁺-montmorillonite 22A or Na⁺-Volclay in aqueous, pH 8 solution gives a 50–60% yield of dimers and trimers (pA)₂ and (pA)₃. The ratio of 3,5-phosphodiester bond formation is twice as great as 2,5-bond formation. The reaction requires the presence of Mg²⁺ and is inhibited by 0.4 M imidazole. N-methylimidazole enhances the rate of the reaction but does not cause major changes in yield or product composition. Higher yields were obtained when Li⁺- or Ca²⁺-montmorillonites were used in place of Na⁺-montmorillonite. Little or no phosphodiester bond formation was observed with Mg²⁺- or Al³⁺-montmorillonite. Montmorillonites other than 22A and Volclay exhibited little or no catalysis. In addition, little or no catalysis was exhibited in ferrugenous smectite, nontronite, allophane, imogolite or sepiolite. Oligomers were also formed by the reaction of ImpG, 2-methylImpG, ImpC and ImpU in the presence of Na⁺-montmorillonite. The pyrimidine nucleotides gave significantly lower yields of oligomers.     

SULFOXIDE-METAL EXCHANGE FOR THE SYNTHESIS OF THE 2′-TRIBUTYLSTANNYL DERIVATIVE OF 2′,3′-DIDEHYDRO-2′,3′-DIDEOXYURIDINE (d4U): A GENERAL ENTRY TO 2′-CARBON-SUBSTITUTED ANALOGUES OF d4U

ABSTRACT

Methods are described for the synthesis of the 2′-tributylstannyl derivative of 2′,3′-didehydro-2′, 3′-dideoxyuridine (d4U). Two approaches were investigated: radical-mediated desulfonylative stannylation of the 2′-benzenesulfonyl derivative of d4U and sulfoxide-metal exchange reaction of the 2′-benzenesulfinyl derivative. The latter approach was found to give the desired 2′-stannyl derivative in good yield. It was also shown that manipulations of the stannyl group allowed the introduction of a variety of carbon-substituents to the 2′-position by applying the Stille reaction. The whole reaction sequence has opened up a highly general entry to 2′-carbon-substituted analogues of d4U.     

Protection of the Lactam Function of 2′-Deoxyinosine with A 2-(4-Nitrophenyl)-Ethyl Moiety

Abstract

The reaction of O-protected inosine with p-nitrophenyl ethanol under Mitsunobu conditions yields a mixture of the 1- and 0° -alkylated derivatives. 2′-Deoxyinosine protected on 0⁶ -, can be synthesized fairly easy from deoxyguanosine with a Mitsunobu reaction followed by reductive deamination.     

Effect of adenosine 3′,5′-(cyclic)-monophosphate on the synthesis of progestational steroids by rabbit ovarian tissue in vitro

1. Adenosine 3',5'-(cyclic)-monophosphate (3',5'-AMP) stimulates the synthesis of progestational steroids by rabbit ovarian tissue in vitro. 2. Other adenosine phosphates fail to increase steroidogenesis. 3. The ratio of 20alpha-hydroxypregn-4-en-3-one to progesterone, the maximal response of the tissue, and the responses of separated corpora lutea and interstitial tissue produced by luteinizing hormone are closely paralleled by 3',5'-AMP. 4. In tissues maximally stimulated by luteinizing hormone, 3',5'-AMP fails to produce an additional response. 5. The addition of theophylline, an inhibitor of phosphodiesterase, potentiates the effects of 3',5'-AMP and also luteinizing hormone. 6. The results obtained suggest that 3',5'-AMP is a mediator of the action of luteinizing hormone on progestational steroid synthesis by rabbit ovarian tissue.     

Pharmacokinetics of A New Anti-HIV Ageht: 2′,3′-Dideoxy-2′,3′-Didehydrothymidine (d4T)

Abstract

D4T is one of several drugs being considered for antiretroviral therapy in the treatment of AIDS. Pharmacokinetic studies showed that d4T was well absorbed, predominantly eliminated as unchanged drug and able to penetrate the blood-brain barrier.