Molecular Evidence for the Existence of Two Species of Marteilia in Europe

Marteilia refringens is one of the most significant pathogens of bivalve molluscs. Previous sequencing of the small subunit ribosomal RNA gene of M. refringens isolates derived from the infected mussels (Mytilus edulis and Mytilus galloprovinciallis) and the oyster (Ostrea edulis) in Europe did not reveal genetic polymorphisms despite indications from epizootiological data that distinct types may exist. We investigated the existence of polymorphisms in the internal transcribed spacer region of the ribosomal RNA genes. The sequences of this region proved to be clearly dimorphic among Marteilia from five sampling sites. The distribution of the two genetic types, named "O" and "M", appeared to be linked to the host species, oysters and mussels, respectively. We therefore support the recognition of two species of Marteilia in Europe and propose that the "O" type corresponds to M. refringens and the "M" type to M. maurini.     

Unnatural enantiomers of 5-azacytidine analogues: syntheses and enzymatic properties

2'-Deoxy-beta-L-5-azacytidine(L-Decitabine), beta-L-5-azacytidine, and derivatives were stereospecifically prepared starting from L-ribose or L-xylose. D- and L-enantiomers of 2'-deoxy-beta-5-azacytidine were weak substrates of human recombinant deoxycytidine kinase (dCK), whereas both enantiomers of beta-5-azacytidine or the L-xylo-analogues were not substrates of the enzyme. None of the reported derivatives of beta-L-5-azacytidine was a substrate of human recombinant cytidine deaminase (CDA).     

Synthesis and in vitro activity of D- and L-enantiomers of 5-(trifluoromethyl)uracil nucleoside derivatives

Recently, beta-L-nucleoside analogues have emerged as a new class of sugar modified nucleosides with potential antiviral and/or antitumoral activity. As a part of our ongoing research on this topic, we decided to synthesize 5-CF3-beta-L-dUrd (7), the hitherto unknown L-enantiomer of Trifluridine, an antiherpetic drug approved by FDA but only used in topical applications due to concomitant cytotoxicity. 5-CF3-beta-L-dUrd (7) as well as some other related L-nucleoside derivatives were stereospecifically prepared and tested in vitro against viral (HSV-1 and HSV-2) and human thymidine kinases (TK).     

Anti-HBV specific beta-L-2'-deoxynucleosides

A unique series of simple unnatural L-nucleosides that specifically inhibit hepatitis B virus (HBV) replication has been discovered. These molecules have in common a hydroxyl group in the 3'-position (3'-OH) of the beta-L-2'-deoxyribose sugar that confers antiviral activity specifically against hepadnaviruses. Replacement of the 3'-OH broadens activity to other viruses. Substitution in the base decreases antiviral potency and selectivity. Human DNA polymerases and mitochondrial function are not effected. Plasma viremia is reduced up to 8 logs in a woodchuck model of chronic HBV infection. These investigational drugs, used alone or in combination, are expected to offer new therapeutic options for patients with chronic HBV infection.     

Megagametophyte-derived linkage maps of white spruce ( Picea glauca) based on RAPD,SCAR and ESTP markers

We have constructed linkage maps for two parents of white spruce [ Picea glauca (Moench) Voss]. Haploid megagametophytes from 92 and 96 seeds of parents M2 and 80132, respectively, were analysed with RAPD, SCAR and ESTP markers. Fragments segregating in a 1:1 Mendelian ratio were classified and mapped using MAPMAKER, GMENDEL and JOINMAP. For M2, the analysis with JOINMAP resulted in 165 loci (152 RAPDs, 3 SCARs and 10 ESTPs) mapping to 23 linkage groups and covering 2,059.4 cM(Kosambi function, K). For 80132, the analysis resulted in 144 loci (137 RAPDs, 1 SCAR and 7 ESTPs) mapping to 19 linkage groups and covering 2,007.7 cM(K). The maps covered 87 and 73% of the entire genome of parents M2 and 80132, respectively. Similar results were obtained with MAPMAKER and GMENDEL. A comparison was made between the two individual maps and 16 loci were shared between the two maps.     

Synthesis and studies of 3'-C-trifluoromethyl-beta-D-ribonucleosides bearing the five naturally occurring nucleic acid bases

3'-C-Trifloromethyl-beta-D-ribonucleoside derivatives bearing the five naturally occurring nucleic acid bases have been synthesized. All these derivatives were prepared by glycosylation reactions of purine and pyrimidine bases with a suitable peracylated 3-C-trifluoromethyl ribofuranose precursor. After deprotection, the resulting title nucleoside analogues were tested for their inhibitory properties against the replication of HIV, HBV and several RNA viruses. However, none of these compounds showed significant antiviral activity.     

Synthesis and biological evaluation of some 5-nitro- and 5-amino derivatives of 2'-deoxycytidine, 2',3'-dideoxyuridine, and 2',3'-dideoxycytidine

In this article, we describe the synthesis of 5-nitro-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)cytosine (4alpha), 5-nitro-1-(2-deoxy-beta-D-erythro-pentofuranosyl)cytosine (4beta), 5-amino-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)cytosine (5alpha), 5-nitro-1-(2-deoxy-beta-D-erythro-pentofuranosyl)cytosine (5beta), 5-nitro-1-(2,3-dideoxy-beta-D-ribofuranosyl)uracil (6beta), 5-amino-1-(2,3-dideoxy-alpha,beta-D-ribofuranosyl)uracil (7), 5-nitro-1-(2,3-dideoxy-alpha,beta-D-ribofuranosyl)cytosine (8) and 5-amino-1-(2,3-dideoxy-beta-D-ribofuranosyl)cytosine (9beta). The prepared compounds were tested for their activity against HIV and HBV viruses, but they did not show significant activity.     

Monoval-LdC: efficient prodrug of 2'-deoxy-beta-L-cytidine (L-dC), a potent and selective anti-HBV agent

In order to improve the oral bioavailability of LdC, valinyl esters were prepared as prodrugs. We report here the syntheses of the 3'-mono-, 5'-mono, and 3',5'-di-O-valinyl esters of LdC. The comparison of their ease of synthesis, their physicochemical properties, as well as their pharmacokinetic parameters in cynomologus monkeys has revealed 3'-mono-O-valinyl derivative as the most promising of the studied prodrugs. This compound is being developed as a new anti-HBV agent.     

Mononucleoside SATE glucosyl phosphorothiolates as a new series of pronucleotides

The synthesis and the study of two phosphorothiolate derivatives of 3'-azido-2',3'-dideoxythymidine (AZT) bearing a S-pivaloyl-2-thioethyl (tBuSATE) group and glucosyl residues associated to the phosphorus atom by a 2-oxyethyl link, are reported. These derivatives could be considered as prototypes of a new series of nucleotide prodrugs (pronucleotides).     

Synthesis and antiviral evaluation of the beta-L-enantiomers of some thymine 3'-deoxypentofuranonucleoside derivatives

3'-Deoxy-beta-L-erythro- (3), 3'-deoxy-beta-L-threo- (6), 2'-fluoro- (7) and 2'-azido-2',3'-dideoxy-beta-L-erythro- (10) pentofuranonucleoside derivatives of thymine have been synthesized and their antiviral properties examined. All these derivatives were stereospecifically prepared by glycosylation of thymine with a suitable peracylated 3-deoxy-L-erythro-pentofuranose sugar (1), followed by appropriate chemical modifications. The prepared compounds were tested for their activity against HIV, but they did not show an antiviral effect.