Studies Towards the Large Scale Chemical Synthesis of the Precursors of Ribonucleosides-3′,4′,5′,5″- 2H 4 and -2′,3′,4′,5′,5″- 2H 5

Abstract

A summary delineating the large scale synthetic studies to prepare labeled precursors of ribonucleosides-3′,4′,5′,5″- ²H ₄ and -2′,3′,4′,5′,5″- ²H ₅ from D-glucose is presented. The recycling of deuterium-labeled by-products has been devised to give a high overall yield of the intermediates and an expedient protocol has been elaborated for the conversion of 3-O-benzyl-α,β-D-allofuranose-3,4-d ₂ 6 to 1-O-methyl-3-O-benzyl-2-O-t-butyldimethylsilyl-α,β-D-ribofuranose-3,4,5,5′-d ₄ 16 (precursor of ribonucleosides-3′,4′,5′,5″- ²H ₄ ) or to 1-O-methyl-3,5-di-O-benzyl-α,β-D-ribofuranose-3,4,5,5′-d ₄ 18 (precursor of ribonucleosides-3′,4′,5′,5″- ²H ₄ ).     

In vivo binding of 2,3,6,2′,3′,6′-hexachlorobiphenyl and 2,4,5,2′,4′,5′-hexachlorobiphenyl to mouse liver macromolecules

The role of metabolic activation in the binding of polychlorinated biphenyls (PCBs) to cellular macromolecules was investigated in vivo by comparing the relative binding of 2,4,5,2′,4′,5′-[U-¹⁴C]hexachlorobiphenyl (2,4,5), a slowly metabolized PCB, with that of 2,3,6,2′,3′,6′-[U-¹⁴C]hexachlorobiphenyl (2,3,6), a rapidly metabolized PCB, and the appropriate controls. Each hexachlorobiphenyl was administered to mice, orally for 5 days (7.28 mg/kg/day). Following the dosing schedule, animals were killed at 1, 5 and 8 days. The concentration of each PCB was determined in liver, muscle and kidney and in purified macromolecules isolated from those tissues. The concentration of 2,4,5 was consistently higher than the concentration of 2,3,6 in all tissues studied. However, the amount of 2,3,6 bound to the purified macromolecules was consistently at least one order of magnitude greater than that of 2,4,5. The greatest binding was observed in RNA followed by protein and DNA, respectively. The purity of the macromolecules and the presence of PCB-derived radioactivity at the monomer level were confirmed. This is the first report of ¹⁴C-labeled PCB being bound to purified RNA, DNA, and proteins isolated from the tissues of animals treated in vivo. The binding is thought to be covalent and to be the result of metabolic activation.     

Natural and synthetic diastereoisomeric (?)-3′,4′,7-trihydroxyflavan-3,4-diols

1. Rhodesian copalwood (Guibourtia coleosperma) contains three diastereo-isomeric leuco-fisetinidins. These consist of the (−)-2,3-cis–3,4-cis (2R,3R,4R) and (−)-2,3-cis–3,4-trans (2R,3R,4S) 3′,4′,7-trihydroxyflavan-3,4-diols, and the third was shown to be a 2,3-trans–3,4-cis isomer by means of paper ionophoresis. 2. There occurrence in similar proportions as tannin precursors also in the tropical hardwoods G. tessmannii and G. demeusii implies a close taxonomic relationship between these, and with G. coleosperma. 3. Epimerization of the natural (−)-3′,4′,7- trihydroxy-2,3-trans-flavan-3,4-trans-diol affords a mixture from which the (−)-2,3-cis–3,4-cis isomer was separated readily, but the (−)-2,3-trans–3,4-cis isomer was obtained with difficulty. These were formed by epimerization of the (−)-2,3-trans–3,4-trans isomer at C-2 and C-4, and at C-4, respectively.     

Phosphonates Derivatives of 2′,3′-Dideoxy-2′,3′-didehydro-pentopyranosyl Nucleosides

Abstract

Adenine and thymine derivatives of 2′,3′-dideoxy-2′,3′-didehydropento-pyranosyl nucleosides carrying a phosphonomethyl moiety at their 4′-O-position and in a cis relationship with the heterocyclic base have been synthesized.     

Synthesis of 3′,4′-C-Bishydroxymethyl-2′,3′,4′-trideoxy-β-L-threo-pentopyranosyl Nucleosides as Potential Inhibitors of HIV

Abstract

The synthesis of 3′,4′-bishydroxymethyl-2′,3′,4′-trideoxy pentopyranosyl derivatives of thymine, uracil, cytosine, and adenine is described. trans-(3S,4S)-Bis(methoxycarbonyl)cyclopentanone (3) was converted to 1-O-acetyl-3,4-C-bis[(tert-butyldiphenylsiloxy)methyl]-2,3,4-trideoxy-α,β-L-threo-pentopyranose (6), which was subsequently condensed with the silylated purine and pyrimidine bases.     

Hydrogenolysis of benzylidene acetals: synthesis of benzyl 2,3,6,2′,3′,4′-hexa-O-benzyl-β-cellobioside, -maltoside,and -lactoside,benzyl 2,3,4,2′,3′,4′-hexa-O-benzyl-β-allolactiside,and benzyl 2,3,6,2′,3′,6′-hexa-O-benzyl-β-lactoside

Hydrogenolysis of benzyl penta-O-benzyl-4′,6′-O-benzylidene-β-cellobioside (4), -maltoside (5), and -allolactoside (16) with LiAlH₄-AlCl₃ gave only the corresponding derivatives having HO-6′ free, in yields of 55, 78, and 90%, respectively. The main product of the hydrogenolysis of benzyl penta-O-benzyl-4′,6′-O-benzylidene-β-lactoside (6) also had HO-6′ free, but the isomer having HO-4′ free was also isolated. The role of the C-1 substituent in the galactose moiety in the direction of benzylidene ring-cleavage is discussed.     

Synthesis of 1′,2′-methano-2′,3′-dideoxynucleosides as potential antivirals

The synthesis of constrained nucleosides has become an important tool to understand the SAR in the interaction between biological and synthetic nucleotides in the context of antisense oligonucleotide therapy. The incorporation of a cyclopropane into a furanose ring of a nucleoside induces some degree of constrain without affecting significantly the steric environment of a nucleoside. Here, we report a new, short and stereocontrolled synthesis of two constrained nucleosides analogues, 1′,2′- methano-2′,3′-dideoxyuridine 9, and the corresponding cytidine analog 12. X-ray crystallography revealed that the furanose ring in the constrained uridine and cytidine analogues was flattened with virtual loss of pseudorotation. The phosphoramidate esters of the novel constrained uridine and cytidine nucleosides, intended as prodrugs, were tested in cell-based assays for viral replication across the herpes virus family and HIV inhibition courtesy of Merck laboratories, Rahway. They were also tested in antiproliferative assays against colorectal and melanoma cell lines. Unfortunately, none of the compounds showed activity in these assays.     

Synthesis and Reactions of Some 3′,4′-Unsaturated 2′,3′-Secouridine Analogues

Abstract

2′,3′-Dibromo-2′,3′-dideoxy-5′-O-trityl-2′,3′-secouridine (8) with sdKF gave the 3′,4′-didehydro-2,2′-anhydro nucleoside 9, which was deprotected to 10. Hydrolysis of 9 gave 3′,4′-didehydro-3′-deoxy-5′-O-trityl-2′,3′-secouridine (11a). Similarly, compound 9 with pyridinium halides gave the corresponding 2′-deoxy-2′-halo nucleosides (11b-d). Compound 11d with azide ion gave 2′-azido analogue 11e. Compound 9 with an excess amount of azide ion gave the 2′-azido triazole (13).     

The synthesis of 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate from lactose

Reaction of methyl 4′,6′-di-O-mesyl-β-lactoside pentabenzoate (8), synthesised via the 4′,6′-O-benzylidene derivative (6), with sodium azide in hexamethylphosphoric triamide gave three products. In addition to the required 4′,6′-diazidocellobioside (9), an elimination product, methyl 4-O-(6-azido-2,3-di-O-benzoyl-4,6-dideoxy-α-L-threo-hex-4-enopyranosyl)-2,3,6-tri-O-benzoyl-β-D-glucopyranoside (12), and an unexpected product of interglycosidic cleavage, methyl 2,3,6-tri-O-benzoyl-β-D-glucopyranoside (13), were formed. The origin of the latter product is discussed. The diazide 9 was converted into 4′,6′-diacetamido-4′,6′-dideoxycellobiose hexa-acetate (16) by sequential debenzoylation, catalytic reduction, acetylation, and acetolysis.     

Influence of Acetyl and Bromine Substitutions on Stacking. Crystal and Molecular Structures of 8-Bromo 2′,3′,5′-Triacetyl Adenosine and 8-Bromo 2′,3′,5′-Triacetyl Guanosine

Abstract

The three dimensional structures of 8-bromo 2′,3′,5′-triacetyl adenosine (8-Br Tri A) and 8-bromo 2′,3′,5′-triacetyl guanosine (8-Br Tri G) have been determined by single crystal X-ray diffraction methods to study the combined effect of bromine and acetyl substitutions on molecular conformation and interactions. The ribose puckers differ from those found in unbrominated Tri A and Tri G and unacetylated 8-Br A and 8-Br G analogues. The adenine bases in 8-Br Tri A form A.A.A base triplets using both Watson-Crick and Hoogsteen sites. Br atoms are not involved in stacking unlike most halogenated structures. The ‘scorpion tail’ positioning of acetyl over base in 8-Br Tri G is different from Tri G and is an interesting consequence of bromine substitution.     

Nucleosides VIII: 1 Synthesis of 2′, 3′-Dideoxy- and 2′, 3′-Didehydro-2′, 3′-Di Deoxyisoguanosine as Potential Antiretroviral Agents

Abstract

2′, 3′-Didehydro-2′, 3′-dideoxyisoguanosine (2) and 2′, 3′- dideoxyisoguanosine (3) have been synthesized by utilizing the Corey-Winter approach starting from isoguanosine. The 6-amino and 5′-hydroxy biprotected isoguanosine derivative was converted to the corresponding 2′, 3′- thionocarbonate, which was heated with triethyl phosphite to afford the 2′,3′- olefinic product. Either a tert-butyldimethylsilyl or a 4, 4′-dimethoxytrityl group was used in the protection of 5′-hydroxy function. Compounds 2 and 3 were found inactive against human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), and herpes simplex virus type 1 (HSV-1).

     

Reduction of excess sludge production by 3,3′,4′, 5-tetrachlorosalicylanilide in an activated sludge process

The potential of 3,3,4,5-tetrachlorosalicylanilide (TCS) addition to an activated sludge continuous process to reduce excess sludge production by disrupting coupling between anabolism and catabolism was investigated. TCS was chosen as a metabolic uncoupler for continuous test in a lab-scale completely mixed activated sludge process. TCS reduced sludge yield by approximately 30% at a dosage of 40 mg/day. Substrate removal capability was not adversely affected by the presence of TCS, but effluent nitrogen concentration increased during the 60-day continuous operation. Sludge settleability of treated and control samples was qualitatively comparable and not significantly different. Microbial activities in terms of specific oxygen uptake rate were also enhanced, and the microbial population was altered. The results suggest that TCS is an effective chemical uncoupler that reduces sludge yield; process performance was not significantly affected by introduction of the uncoupler.     

Synthesis of 2′,3′-Dideoxyribavirin

Abstract

A synthesis of 1-(2,3-dideoxy-β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (2′,3′-dideoxyribavirin, ddR) is described. Glycosylation of the sodium salt of 1,2,4-triazole-3-carbonitrile (5) with 1-chloro-2-deoxy-3,5-di-0-p-toluoyl-α-D-erythro-pentofuranose (1) gave exclusively the corresponding N-1 glycosyl derivative with β-anomeric configuration (6), which on ammonolysis provided a convenient synthesis of 2′-deoxyribavirin (7). Similar glycosylation of the sodium salt of methyl 1,2,4-triazole-3-carboxylate (2) with 1 gave a mixture of corresponding N-1 and N-2 glycosyl derivatives (3) and (4), respectively. Ammonolysis of 3 furnished yet another route to 7. A four-step deoxygenation procedure using imidazolylthiocarbonylation of the 3′-hydroxy group of 5′-0-toluoyl derivative (9a) gave ddR (11). The structure of 11 was proven by single crystal X-ray studies. In a preliminary in vitro study ddR was found to be inactive against HIV retrovirus.     

New Approach to the Synthesis of 2′,3′-dideoxyadenosine and 2′,3′-Dideoxyinosine

Abstract

A new approach to the synthesis of 2′,3′-dideoxyadenosine and 2′,3′-dideoxyinosine based on deoxygenation of 2′,3′-di-O-mesylnucleosides was developed.     

1′, 2′-Seco-2′,3′-Dideoxynucleoside Analogues: Synthesis and Antiviral Evaluation of Racemic Trans-[1′, 5′-Dihydroxy 3′, 4′-methylenylpent-2′-oxy)methyl] Nucleosides

Abstract

Reaction of (±)but-3-en-1,2-diol (3) with ethyl diazoacetate afforded two cyclopropyl compounds (5) and (6). Their relative trans stereochemistry at C-2 and C-3 has been determined by high-field and computational NMR spectroscopy. (±)Trans-1-(1′,5′-dihydroxy-3′,4′-methylenyl-pent-2′-oxy)methyl]thymine (1d) or -cytosine (1b) and (±)trans-9-(1′,5′-dihydroxy-3′,4′-methylenylpent-2′-oxy)-methyl]adenine (la) or -guanine (1c) have been obtained through a regiospecific alkylation procedure and their antiviral evaluation is reported.     

Synthesis of 2′,3′-Didehydro-2′,3′-Dideoxy-3′-C-Methyl Substituted Nucleosides

Abstract

1-(2,3-Dideoxy-3-C-hydroxmethyl-β-D-threo-pentofuranosyl) -,1- (2,3-didehydro-2,3-dideoxy-3-C-hydroxymethyl-β-D-glycero- pentofuranosyl) -and 1-(3-C-azidomethyl-2,3-dideoxy-3-C-hydroxymethyl-β-D-glycero- pentofuranosyl)uracil, thymine and cytosine were synthesized and evaluated for anti-HIV activity. The synthetic strategy was based on an allylic alcohol transposition of the corresponding 3′-C-methylene-nucleoside analogues.