A new cyclic phosphoramidate D4T prodrug approach cycloAmb-D4T-phosphoramidates.

A new potential phosphoramidate prodrug approach for d4T 1 is described. In hydrolyses studies the cycloAmb-d4T-phosphoramidates 2 and 3 proved to deliver d4TMP following a tandem reaction.     

Synthesis and Biological Evaluation of some Acyclic Nucleoside Cyclic Phosphoramidate Derivatives

Abstract

The acyclic nucleosides 2 were treated with 2-chloro-3-methyl-1-oxa-3-aza-2-phosphacyclopentane (3) in the presence of diisopropylethylamine to give the corresponding phosphoramidite derivatives (4). The phosphoramidite intermediates (4) were oxidized with m-chloroperbenzoic acid to the phosphoramidate derivatives (5). Treatment of 5a,b with ZnBr₂ in CH₃NO₂ gave the corresponding acyclic nucleoside cyclic phosphoramidates (6a,b). Attempts to desilylation of 5c by tetrabutylammonium fluoride (TBAF) resulted in opening of the phosphoramidate ring. The newly synthesized compounds were evaluated for antiviral and antitumor cell activity.     

A New Approach to the Synthesis of Linear and Cyclic Oligoribonucleotides

Abstract

The tetraribonucleoside triphosphate 15 and the cyclic tetraribonucleotide 16 have been prepared by a recently reported triester approach in solution, involving H-phosphonate coupling.     

3-Substituted Pyrazinone Nucleosides—A New Family of D4T Analogues

The synthesis of a new family of D4T analogues is described to study the influence of pyrazinone base on antiretroviral power. Substitution of 3H by methyl or n-decyl increases the lipophilic character and may facilitate diffusion across cell membranes. The compounds were characterized by ¹H NMR and infrared spectroscopy. Antiviral (HIV-1) properties of these compounds were examined.     

A New 4D Trajectory-Based Approach Unveils Abnormal LV Revolution Dynamics in Hypertrophic Cardiomyopathy

The assessment of left ventricular shape changes during cardiac revolution may be a new step in clinical cardiology to ease early diagnosis and treatment. To quantify these changes, only point registration was adopted and neither Generalized Procrustes Analysis nor Principal Component Analysis were applied as we did previously to study a group of healthy subjects. Here, we extend to patients affected by hypertrophic cardiomyopathy the original approach and preliminarily include genotype positive/phenotype negative individuals to explore the potential that incumbent pathology might also be detected. Using 3D Speckle Tracking Echocardiography, we recorded left ventricular shape of 48 healthy subjects, 24 patients affected by hypertrophic cardiomyopathy and 3 genotype positive/phenotype negative individuals. We then applied Generalized Procrustes Analysis and Principal Component Analysis and inter-individual differences were cleaned by Parallel Transport performed on the tangent space, along the horizontal geodesic, between the per-subject consensuses and the grand mean. Endocardial and epicardial layers were evaluated separately, different from many ecocardiographic applications. Under a common Principal Component Analysis, we then evaluated left ventricle morphological changes (at both layers) explained by first Principal Component scores. Trajectories’ shape and orientation were investigated and contrasted. Logistic regression and Receiver Operating Characteristic curves were used to compare these morphometric indicators with traditional 3D Speckle Tracking Echocardiography global parameters. Geometric morphometrics indicators performed better than 3D Speckle Tracking Echocardiography global parameters in recognizing pathology both in systole and diastole. Genotype positive/phenotype negative individuals clustered with patients affected by hypertrophic cardiomyopathy during diastole, suggesting that incumbent pathology may indeed be foreseen by these methods. Left ventricle deformation in patients affected by hypertrophic cardiomyopathy compared to healthy subjects may be assessed by modern shape analysis better than by traditional 3D Speckle Tracking Echocardiography global parameters. Hypertrophic cardiomyopathy pathophysiology was unveiled in a new manner whereby also diastolic phase abnormalities are evident which is more difficult to investigate by traditional ecocardiographic techniques.     

New Approach to the Solid Phase Synthesis of N3′→P5′ Phosphoramidate Oligonucleotides

Abstract

LCA-CPG-nucleoside 5′-O-(O-β-cyanoethyl-H-phosphonates) react with 3′-amino-2′,3′-dideoxynucleoside in the presence of iodine giving in a high yield N3′→P5′ phosphoramidate oligonucleotides.     

A Prodrug Approach to the Use of Coumarins as Potential Therapeutics for Superficial Mycoses

Superficial mycoses are fungal infections of the outer layers of the skin, hair and nails that affect 20–25% of the world''s population, with increasing incidence. Treatment of superficial mycoses, predominantly caused by dermatophytes, is by topical and/or oral regimens. New therapeutic options with improved efficacy and/or safety profiles are desirable. There is renewed interest in natural product-based antimicrobials as alternatives to conventional treatments, including the treatment of superficial mycoses. We investigated the potential of coumarins as dermatophyte-specific antifungal agents and describe for the first time their potential utility as topical antifungals for superficial mycoses using a prodrug approach. Here we demonstrate that an inactive coumarin glycone, esculin, is hydrolysed to the antifungal coumarin aglycone, esculetin by dermatophytes. Esculin is hydrolysed to esculetin β-glucosidases. We demonstrate that β-glucosidases are produced by dermatophytes as well as members of the dermal microbiota, and that this activity is sufficient to hydrolyse esculin to esculetin with concomitant antifungal activity. A β-glucosidase inhibitor (conduritol B epoxide), inhibited antifungal activity by preventing esculin hydrolysis. Esculin demonstrates good aqueous solubility (<6 g/l) and could be readily formulated and delivered topically as an inactive prodrug in a water-based gel or cream. This work demonstrates proof-of-principle for a therapeutic application of glycosylated coumarins as inactive prodrugs that could be converted to an active antifungal in situ. It is anticipated that this approach will be applicable to other coumarin glycones.     

A new type of UV-sensitive mutant of phage T4D

Within a group of more than 20 UV-sensitive mutants of T4D, 4 UV-sensitive mutants with the same sensitivity as T4 x were isolated independently of each other. They were uvs9, uvs21, uvs35, and uvs52. The double mutants with x and y₁₀ were constructed: they are slightly more UV sensitive than T4 v₁. The double mutant with uvs5 was not found. The mutations of uvs9, 21, 35, and 52 are closely linked with v₁. The photoreactivable sector (PRS) is 0.4. One of the mutants, uvs52, has the same sensitivity for methyl methanesulphonate (MMS) as T4⁺, shows a stronger multiplicity reactivation than the wild type, shows the same sensitivity relative to T4⁺ and T4 v₁ in Luria-Latarjet tests and in monocomplex UV inactivation, and raises the recombinant frequency in crosses with irradiated phage. The uvs52⁺ function has the same sensitivity to UV as the v⁺ function. Complementation between uvs52 and v₁, if present is difficult to demonstrate owing to an appreciable MR contribution to increased survival. The possibility that uvs52 is an allele of v₁ is discussed. The observations fit the assumption that uvs52 is an excision-repair mutant with a low excision rate.     

Lithiation study on D4T.

Upon treatment with LTMP, 5'-O-protected D4T undergoes deprotonation of the vinylic proton (H-3' or H-2'): when 5'-O-silyl derivative was used, the 3'-C-silylated product was formed as a result of C3'-lithiation and subsequent O-->C silyl migration, while deprotonation at the 2'-position led to the formation of an allene derivative. A stannyl version of this reaction was also examined to develop a method for C3'-functionalization of D4T.     

A Practical and Stereospecific Approach to the Synthesis of 3′-Deoxy-2′,3′-didehydrothymidine (D4T)

Abstract

Starting with D-glucose, 5-t-butyldimethylsilyl-3-deoxy-D-arabinose (5) was prepared. Condensation of 5 with cyanamide followed by reaction of the resulting oxazoline 6 with methyl-2-formylpropionate furnished the anhydronucleoside 7. t-Butoxide elimination of 7 gave the target compound in moderate yields due to concomitant 1′,2′-double bond formation. However, phenylselenolate and phenylthiolate opened 7 regiospecifically to the corresponding seleno and thio compounds, 10 and 11, respectively. Oxidative elimination of 10 and the pivaloyl derivative 12 gave 5′-t-butyldimethylsilyl (8) and 5′-pivaloyl (13) D₄T in excellent yield.     

Folate polyglutamates in T4D bacteriophage and T4D-infected Escherichia coli.

The folate compound which is a structural component of the Escherichia coli T-even bacteriophage baseplates, has been identified as the hexaglutamyl form of folic acid using a new chromatographic procedure (Baugh, C.M., Braverman, E. and Nair, M.G. (1974) Biochemistry 13, 4952-4957). It has also been found that the host cell contains a variety of polyglutamyl forms of folic acid. The major form is the triglutamate (about 50%) but small amounts of higher molecular weight folates including the octaglutamate (1.8%) have been identified. Upon infection with wild-type T4D bacteriophage there is a shift in the distribution of the folate compounds so that the folyl polyglutamyl compounds having the higher molecular weights are increased. Infection of E. coli with baseplate mutants of T4D containing an amber mutation in gene 28 resulted in the formation of significant amounts (over 7%) of folate compound(s) of molecular weight much higher than those observed either in uninfected cells or cells infected with wild-type T4D. It is suggested that the T4D gene 28 product functions to cleave glutamate residues from high molecular weight folyl polyglutamates to increase the availability of the folyl hexaglutamate for virus assembly.     

四棱草中的一个新环八肽

从四棱草（Schnabalia oligophylla Hand.-Mazz.）全草的甲醇提取物中分离得到一个新的环八肽,命名为四棱草环肽（1）。用波谱方法鉴定了1的结构,并以通过HPLC手性柱分析指定了除脯氨酸和甘氮酸外的氨基酸的绝对构型。活性实验显示,四棱草环肽（1）对T／B淋巴细胞有免疫抑制作用,另外,从该植物中还分离鉴定了7个已知化合物。     

A New Cyclic Octopeptide from Schnabelia oligophylla

From the methanol extract of the whole plant of Schnabelia oligophylla Hand.-Mazz. (Lamiaceae), a new cyclic octopeptide, named schnabepeptide (1), was isolated by silica gel chromatography. Its structure was elucidated by spectroscopic analyses and the absolute configuration of the amino acid units, except for proline and glycine, were assigned by chiral HPLC analysis. Bio-assay showed that schnabepeptide (1) exhibited an immunosuppression activity on T/B lymphocytes. Along with the new compound, seven known compounds, octadeca-9,16-dioxo-10(E),12(Z),14(E)-trienoic acid (2), 12,16-epoxy-11,14-dihydroxy-17(15→16),18(4→3)-diabeo-abieta-3,5,8,11,13,15-hexene-2,7-dione (teuvincenone F, 3), abscisic acid (4), β-sitosterol (5), daucosterol (6), stigmasteryl 3-O-β- D -glucopyranoside (7) and palmitic acid (8), were also isolated from this plant.     

Folate polyglutamates in T4D bacteriophage and T4D-infected Escherichia coli

The folate compound which is a structural component of the Escherichia coli T-even bacteriophage baseplates, has been identified as the hexaglutamyl form of folic acid using a new chromatographic procedure (Baugh, C.M., Braverman, E. and Nair, M.G. (1974) Biochemistry 13, 4952–4957). It has also been found that the host cell contains a variety of polyglutamyl forms of folic acid. The major form is the triglutamate (about 50%) but small amounts of higher molecular weightsfolates including the octaglutamate (1.8%) have been identified. Upon infection with wild-type T4D bacteriophage there is a shift in the distribution of the folate compounds so that the folyl polyglutamyl compounds having the higher molecular weights are increased. Infection of E. coli with baseplate mutants of T4D containing an amber mutation in gene 28 resulted in the formation of significant amounts (over 7%) of folate compound(s) of molecular weight much higher than those observed either in uninfected cells or cells infected with wild-type T4D. It is suggested that the T4D gene 28 product functions to cleave glutamate residues from high molecular weight folyl polyglutamates to increase the availability of the folyl hexaglutamate for virus assembly.     

Cyclic Uridine Diphosphate Glucose: A New Pyrimidine Analog of Cyclic ADP Ribose

Abstract

Novel compound 1, as the first example of cyclic ADP-ribose analogs containing a pyrimidine residue, was synthesized by a chemical strategy employing a Mitsunobu reaction for the condensation of the glucosyl moiety on protected uridine, and a Matsuda procedure for the cyclization step.     

Cyclic di‐GMP inactivates T6SS and T4SS activity in Agrobacterium tumefaciens

The Type VI secretion system (T6SS) is a bacterial nanomachine that delivers effector proteins into prokaryotic and eukaryotic preys. This secretion system has emerged as a key player in regulating the microbial diversity in a population. In the plant pathogen Agrobacterium tumefaciens, the signalling cascades regulating the activity of this secretion system are poorly understood. Here, we outline how the universal eubacterial second messenger cyclic di‐GMP impacts the production of T6SS toxins and T6SS structural components. We demonstrate that this has a significant impact on the ability of the phytopathogen to compete with other bacterial species in vitro and in planta. Our results suggest that, as opposed to other bacteria, c‐di‐GMP turns down the T6SS in A. tumefaciens thus impacting its ability to compete with other bacterial species within the rhizosphere. We also demonstrate that elevated levels of c‐di‐GMP within the cell decrease the activity of the Type IV secretion system (T4SS) and subsequently the capacity of A. tumefaciens to transform plant cells. We propose that such peculiar control reflects on c‐di‐GMP being a key second messenger that silences energy‐costing systems during early colonization phase and biofilm formation, while low c‐di‐GMP levels unleash T6SS and T4SS to advance plant colonization.