Nucleic acid related compounds. 53. Synthesis and biological evaluation of 2′-deoxy-β-threo-pentofuranosyl nucleosides. "Reversion to starting alcohol" in Barton-type reductions of thionocarbonates

Treatment of selectively 3′,5′-protected β-D-xylofuranosyl nucleosides (4) with phenyl chlorothionocarbonate and DMAP followed by hydrogenolysis of the resulting (2′-O-phenoxythiocarbonyl) phenyl thionocarbonate esters (6) with tributylstannane/AIBN, and deprotection, gave 2′-deoxy-β-D-threo-pentofuranosyl nucleosides (7). Formation of a by-product bis(nucleosid-2′-yl)thionocarbonate dimer (8) was detected in the uracil nucleoside reaction sequence. Its subsequent reduction provides one explanation for "reversion to starting alcohol" in Barton-type deoxygenation reactions. Only the guanine 2′-deoxynucleoside analogue (7b) had (weak) antiviral activity (against herpes simplex virus type 1).

Structure and conformation of the branch core triribonucleotide containing 2'-5' and 3'-5' phosphodiester linkages (A 2'p5'G 3'p5'C) i solution, essential for yeast mRNA splicing, deduced from 1H-NMR

The non-exchangeable 1H-NMR signals of the branch core trinucleotide of the lariat branch site (A2'p5'G3'p5'C, 1) and its derivatives 2 and 3 are completely assigned using one- and two-dimensional NMR techniques including NOE, COSY, NOESY, 1H-1H INADEQUATE and 2D-J-resolved spectroscopy. From the vicinal coupling constants in the individual ribose rings, NOE data and T1 measurements, the following properties of the trimers are deduced. (i) The unique stacking behavior of the trimers is S2'N3'N, and the sugar rings exist predominantly in the N-conformation (3'-endo-2'-exo). (ii) The sugar-base orientations appear to be anti. (iii) The branched trimers exist in solution as single-stranded right-handed conformations resembling A-RNA with stacking between the adenine and guanine residues in aqueous solution at 21 degrees C and pH 7.2. (iv) The calculated values for the torsion angles epsilon t and gamma+ for the trimers are 201-203 degrees and 71-86%, respectively, while the percent beta t values are higher for the guanine (87-92%) than the cytosine residues (73-77%). The computer generated depiction of the triribonucleotide 1 is also shown. These subtle structural features may act as recognition signals for this critical lariat branch site which is essential for the second step in yeast mRNA splicing.

Design features of a controlled clinical trial to assess the effect of a calcium entry blocker upon the progression of coronary artery disease

This report presents the design and methodological features of a double-blind, randomized, placebo-controlled, trial in 383 patients with coronary artery disease. The study's principal objective is to determine whether chronic treatment with a calcium entry blocker can retard the progression of coronary artery disease. The study population consists of patients with coronary artery disease and a baseline coronary arteriogram that qualifies them as being at high risk for disease progression. After satisfying all entry criteria, patients were randomized to receive either the calcium entry blocker nicardipine or placebo. All indicated concomitant medications except calcium entry blockers are permitted. Patients are being followed clinically for 24 months before undergoing a second coronary arteriogram. The effect of the treatments on a variety of clinical and angiographic parameters will be determined.

Systematic synthesis and biological evaluation of alpha- and beta-D-lyxofuranosyl nucleosides of the five naturally occurring nucleic acid bases

The alpha- and beta-D-lyxofuranosyl analogues of the naturally occurring nucleosides have been synthesized and their antiviral properties examined. The alpha anomers were prepared by glycosylation of purine and pyrimidine aglycons with tetra-O-acetyl-alpha-D-lyxofuranose, followed by removal of the blocking groups. The beta anomers were obtained by sequential oxidation and reduction of 3',5'-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-beta-D-x ylofuranosyl nucleosides. The lyxofuranosyl nucleosides were tested for their activity against a variety of RNA and DNA viruses and for inhibition of cell growth. One compound, 9-alpha-D-lyxofuranosyladenine, showed activity against herpes simplex virus types 1 and 2 both in vitro and in vivo.

Degradation by the 2',5'-phosphodiesterase activity of mouse cells requires the presence of a ribo hydroxyl group in the penultimate position of the oligonucleotide substrate

A series of 9-beta-D-xylofuranosyladenine (xyloA or xyloadenosine) substituted analogs of 2-5A core trimer and tetramer were examined for their ability to be degraded by the 2',5'-phosphodiesterase activity of cytoplasmic extracts of mouse L cells. Two distinct groups of xyloA-substituted analogs could be readily discriminated. The first group contained xyloadenosine at the 2'-termini and included A2'p5'A2'p5'(xyloA) and A2'p5'A2'p5'A2'p5'(xyloA). These oligomers behaved as did their parent oligoadenylates in that they were equally sensitive to degradation by the 2',5'-phosphodiesterase activity. The second group of oligonucleotides bore a xyloadenosine residue in the penultimate nucleotide residues of the oligomers and included A2'p5'(xyloA)2'p5'(xyloA), (xyloA)2'p5'(xyloA)2'p5'(xyloA), A2'p5'A2'p5'(xyloA)2'p5'(xyloA) and (xyloA)2'p5' (xyloA)2'p5'(xyloA)2'p5'(xyloA). This group was quite resistant to 2',5'-phosphodiesterase activity. In all, the findings demonstrate that the ribo configuration 3'-hydroxyl group in the penultimate nucleotide of the oligonucleotide substrate is a prerequisite for the 2',5'-phosphodiesterase activity.

Reversed-phase high-performance liquid chromatography of nucleoside analogues. Simultaneous analysis of anomeric D-xylo- and D-lyxofuranonucleosides and some other D-pentofuranonucleosides

Reversed-phase high-performance liquid chromatography using a C18 column was applied to the analysis of reconstituted mixtures of previously synthesized alpha, beta D-xylo- and D-lyxofuranonucleosides as well as a number of commercially available D-ribo- and D-arabinofuranonucleosides. From a detailed study of various parameters (size of support particles, nature and pH of the mobile phase, temperature), optimized conditions were established. Correlations between the retention times and structures of the bases, the orientations of the secondary hydroxyl groups of the sugar moiety and the anomeric configurations of the nucleosides are also reported.

[The surgical alternative in the treatment of terminal cardiomyopathies: cardiac transplantation]

Between April 1983 and November 1985, 14 patients have undergone a heart transplant, or 10 men and 4 women, aged from 17 to 55 years. The surgical indication was a cardiomyopathy in terminal evolutive phase, of which the etiology was ischemia in 8 cases, congestion in 5 cases and rheumatism in one case. There was one operative death (7.1%) from acute rejection and a late death secondary to chronic rejection. The actuarial rate of survival at one and 2 years was 81.9%. Post-operative complications, most frequent at an early stage, were arterial hypertension (9 cases), rejection (8 cases) and renal insufficiency (6 cases). During an average post-operative evolution of 13 months, 17 rejection episodes occurred in 10 patients (71.4%) and 5 patients (35.7%) presented with 7 infectious episodes, one of them severe. Cyclosporin's toxicity appeared in the immediate post-operative period by an always reversible increase of the bilirubin and creatinin levels. On a long term, all patients present with arterial hypertension, accompanied by a moderate renal insufficiency (creatinin between 2.2 and 2.4 mg%). Among the survivors, 9 patients (75%) remain completely asymptomatic and have resumed normal physical activities. Cardiac transplantation has therefore become a valid therapeutic alternative, able to greatly improve survival and the functional condition of patients with terminal cardiomyopathy.

Systematic synthesis and biological evaluation of alpha- and beta-D-xylofuranosyl nucleosides of the five naturally occurring bases in nucleic acids and related analogues

The alpha- and beta-D-xylofuranosyl analogues of the naturally occurring nucleosides, as well as other D-xylofuranosyl derivatives, have been the subject of a systematic synthesis and examination of their biological, i.e. antiviral antimetabolic, and cytostatic properties. The beta anomers were prepared by glycosylation of purine and pyrimidine aglycons with peracylated 1-O-acetyl-alpha-D-xylofuranoses, followed by removal of the blocking groups. The alpha anomers were obtained by a multistep synthesis with use of 2-amino- or 2-mercapto-alpha-D-xylofuran[1',2':4,5]-2-oxazoline as starting material. The xylofuranosyl nucleosides were tested for their activity against a variety of RNA and DNA viruses and for inhibition of cell growth and macromolecule synthesis. Three compounds, 9-(beta-D-xylofuranosyl)adenine, 9-(beta-D-xylofuranosyl)guanine, and 1-(beta-D-xylofuranosyl)cytosine, showed marked biological activity.

Influence of the xyloadenosine analogue of 2',5'-oligoriboadenylate on poly(A)-specific, 2',5'-oligoriboadenylate degrading 2',3'-exoribonuclease and further enzymes involved in poly(A)(+)mRNA metabolism

The homogeneous poly(A)-specific 2',3'-exoribonuclease from calf thymus gland, which cleaves both 3',5'- and 2',5'-linked oligoriboadenylates, does not degrade (xyloA2'p)2 xyloA, the xylofuranosyladenosine analogue of the 2-5A core. This oligonucleotide, which is supposed to enter intact cells rapidly, was found to possess an increased stability and an enhanced antiherpesvirus activity compared to the natural (A2'p)2A (Eppstein, D.A., Barnett, J.W., Marsh, Y.V., Gosselin, G. and Imbach, J.-L. (1983) Nature 302, 723-724). The poly(A) anabolic enzyme, poly(A) polymerase (Mn2+-dependent), from the same source, which is initiated by (A3'p)2A and its higher oligomers, does not accept 2-5A core and its xyloadenosine analogue as primer. Both oligonucleotides exert no influence on endoribonuclease IV and on the integrity of the poly(A)-ribonucleoprotein complex.

Mechanism of inhibition of herpesvirus growth by 2'-5'-linked trimer of 9-beta-D-xylofuranosyladenine

The 2'-5'-linked trimer of 9-beta-D-xylofuranosyladenine (XyloA)3 is an extremely potent inhibitor of growth of herpes simplex viruses 1 and 2. Evidence is presented that in spite of its increased stability in cell-free extracts (D.A. Eppstein, Y.V. Marsh, B.B. Schryver, M.A. Larsen, J.W. Barnett, J.P.H. Verheyden, and E.J. Prisbe, J. Biol. Chem. 257, 13390-13397, 1982), intact (XyloA)3 was not detected in Vero cells, but instead was rapidly degraded in the medium to monomeric 9-beta-D-xylofuranosyladenine (XyloA). The XyloA thus formed was rapidly taken up by cells, phosphorylated to its triphosphate, and produced inhibition of RNA synthesis. The observed inhibition of DNA synthesis (D.A. Eppstein, Y.V. Marsh, B.B. Schryver, M.A. Larsen, J.W. Barnett, J.P.H. Verheyden, and E.J. Prisbe, J. Biol. Chem. 257, 13390-13397, 1982) and herpesvirus growth by (XyloA)3 (D.A. Eppstein, J.W. Barnett, Y.V. Marsh, G. Gosselin, and J.L. Imbach, Nature (London) 302, 723, 724, 1983) is most likely the result of inhibition of RNA synthesis by its degradation product XyloA.

Conformational characteristics of the trinucleoside diphosphate xyloA2'-5'xyloA2'-5'xyloA. A nuclear magnetic resonance and CD study

In this paper the conformational analysis of the 2'-5' linked xylotrinucleotide xA2'-5'xA2'-5'xA is reported. The title compound is an analogue of A2'-5'A2'-5'A, which compound was shown to display inhibitive effects on protein synthesis. The complete 1H-NMR assignment of the high field spectral region of the xylose trimer is given. Modes of base-base stacking are extracted from coupling constant data at various temperatures. Circular dichroic (CD) spectra confirm the presence of stacked states at low temperature. Xylonucleosides are known to prefer the N-type sugar conformation. However, in the present trimer the S-type conformer is suggested to partake in stacked conformations. Two types of stacking in the two constituent dimer fragments of the trimer are proposed to rationalize the NMR data: xA(1)N-xA(2)S and xA(2)N-xA(3)S.

Xyloadenosine analogue of (A2'p)2A inhibits replication of herpes simplex viruses 1 and 2

Molecules of the structure ppp(A2'p)2A containing a 2' leads to 5' phosphodiester bond, commonly abbreviated as 2-5A, are synthesized in interferon-treated virally-infected cells and have been implicated in several systems as contributing to interferon's antiviral activity. The 2-5A binds to and subsequently activates an endogenous endonuclease, ultimately resulting in degradation of RNA. We have been interested in the use of 2-5A analogues to achieve antiviral activity without the use of interferon. For this approach to be successful, analogues must be synthesized with an increased stability (native 2-5A is rapidly degraded by cellular phosphodiesterases) and with increased ability to enter intact cells. Removal of the highly-negative charged 5' terminal phosphates from ppp(A2'p)2A results in formation of the 'core' species, (A2'p)2A, which should be able to penetrate intact cells more readily. While Kimchi et al. have shown that 2-5A core has an antimitogenic effect in mouse spleen lymphocytes and 3T3 fibroblasts, Williams and Kerr have reported lack of antiviral activity against Semliki Forest virus or encephalomyocarditis virus by exogenously-administered 2-5A core. We have previously determined that (xyloA2'p)2xyloA (abbreviated as xylo 2-5A core), the xyloadenosine analogue of the 5'-terminally dephosphorylated 2-5A core, is over 100 times more stable than the parent 2-5A core species. We now report that this xylo 2-5A core inhibits replication of herpes simplex viruses 1 and 2 in vitro, with greater than 100 times the activity of the parent 2-5A core. The mechanism of antiviral action of the 2-5A core analogue appears to involve a pathway different from that activated by the parent 5' triphosphorylated 2-5A species.

Fat embolism and hemolytic anemia

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Agranulocytosis: a report of 30 cases

Thirty cases of acute agranulocytosis, as defined by Schultz, were observed between 1946 and 1964 at the Hôtel-Dieu Hospital, Montreal. In 14 cases agents incriminated were: aminopyrine, phenylbutazone, sulfonamides and chlorpromazine. Aminopyrine alone was responsible for eight cases. In the remaining 16 cases no definite etiology was established. Clinical manifestations included fever, prostration, angina and multiple pharyngeal ulcerations; these were associated with severe leukopenia and agranulocytosis. The bone marrow showed hypoplasia, lymphocytosis and maturation arrest. Localized and pulmonary infections, pseudomembranous enterocolitis and septicemia were frequent complications in 21 cases and were usually responsible for death, which occurred in 12 cases. Almost all patients who developed septicemia or pseudomembranous enterocolitis died. The pathogenesis is still not clear, but chlorpromazine and its analogues may act as a metabolic inhibitor, while the aminopyrine group probably operates through an immune mechanism.