Synthesis and anti-HBV activity of thiouracils linked via S and N-1 to the 5-position of methyl beta-D-ribofuranoside

Reverse nucleoside derivatives of 2-(methylsulfanyl)uracils 6a-d were prepared by treating of the sodium salt of 2-(methylsulfanyl)uracils (5a-d) with methyl 2,3-O-isopropylidene-5-O-p-toluenesulfonyl-beta-D-ribofuranoside (2). The alkylation of 2-thiouracils 4a-d with methyl 5-deoxy-5-iodo-2,3-O-isopropylidene-D-ribofuranoside (3) afforded the corresponding S-ribofuranoside derivatives 8a-d. Deisopropylidenation of 6a-d and 8a-d afforded the corresponding deprotected derivatives 7a-d and 9a-d, respectively. The Anti-HBV activity of selected compounds was studied.     

Synthesis of new 6-alkylvinyl/arylalkylvinyl substituted 1,2,4-trioxanes active against multidrug-resistant malaria in mice

3-Alkyl/arylalkyl substituted 2-butenols 9, 10, 23a-d undergo regiospecific photooxygenation to furnish beta-hydroxyhydroperoxides 11, 12, 24a-d, respectively, in reasonable yields. Acid catalyzed condensation of 11, 12, 24a-d with various ketones furnish new 1,2,4-trioxanes 13-18, 25a-d, 26a-d, 27a-d in good yields. Several of these trioxanes show promising antimalarial activity against multidrug-resistant Plasmodium yoelii in mice by oral and intramuscular routes.     

Novel side reactions accompanying activation and aminolysis of N-benzoyl-2-alkylserines

2-Phenyl-4-alkyl-4-hydroxymethyl-1,3-oxazolones (2a-d) have been identified as side products accompanying activation of N-benzoyl-2-alkylserines (1a-d). Oxazolones 2a-d in the presence of amine rearrange subsequently to corresponding 4-alkyl-2-phenyl-4,5-dihydro-1,3-oxazole-5 carboxylic acids (4a-d) at a 20-68% yield.     

Orally active 1,2,4-trioxepanes: synthesis and antimalarial activity of a series of 7-arylvinyl-1,2,4-trioxepanes against multidrug-resistant Plasmodium yoelii in Swiss mice

7-Arylvinyl-1,2,4-trioxepanes 7a-d, 8a-d, 9a-d, 10a-d, 11a-c, and 12a-c, prepared by photooxygenation of homoallylic alcohols 5a-d, were evaluated against multi-drug resistant Plasmodium yoelii nigeriensis in Swiss mice by oral and intramuscular routes. Trioxepane 11c, the most active compound of the series, showed more than 98% suppression of parsitaemia at 96 mg/kg by both oral and intramuscular routes. This is the first report on in vivo active 1,2,4-trioxepanes.     

Synthesis and antiprotozoal activity of novel bis-benzamidino imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridines

The key dinitrile intermediates 4a-d were synthesized by reaction of phenacyl bromide 1 and the appropriate 2-amino-5-bromopyridines to yield 3a-d. Suzuki coupling of 3a-d with 4-cyanophenylboronic acid yielded the 2,6-bis(4-cyanophenyl)-imidazo[1,2-a]pyridine derivatives 4a-d. The bis-amidoximes 5a-d, obtained from 4a-d by the action of hydroxylamine, were converted to the bis-O-acetoxyamidoximes which on catalytic hydrogenation in a mixture of ethanol/ethyl acetate gave the acetate salts of 2,6-bis[4-(amidinophenyl)]-imidazo[1,2-a]pyridines 7a-d. In contrast, catalytic hydrogenation of the bis-O-acetoxyamidoxime of 5a in glacial acetic acid gave the saturated analogue 2,6-bis[4-(amidinophenyl)]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine 8. O-Methylation of the amidoximes 5a-d gave the N-methoxyamidines 6a-d. The diamidines showed strong DNA binding affinity, were very active in vitro against T. b. r. exhibiting IC(50) values between 7 and 38nM, but were less effective against P. f. with IC(50) values between 23 and 92nM. Two of the diamidines 7c and 7d were slightly more active than furamidine but less active than azafuramidine in the T. b. r. STIB900 mouse model. Only one prodrug 6b showed moderate activity in the same mouse model.     

Synthesis of 3''-phosphates of diribonucleoside monophosphates via phosphotriester intermediates.

Phosphorylation of the easily accessible 3',5'-diesters 1a-d with diphenyl phosphorochloridate, followed by selective 5'-deacylation, affords the phosphotriester derivatives 2a-d in good yields. Alkaline treatment of 2a-d results in the formation of the 2',3'-cyclic phosphates (3a-d). The usefulness of the phosphotriester derivatives 2a-d is also demonstrated in the synthesis of the nucleotidyl-(3'-5')nucleoside 3'-phosphates U-Up (10a), U-Ap (11a), U-Cp (12a) and A-Gp (13a). The fully protected dinucleoside diphosphates 5c-8c, prepared by the phosphotriester method, are deprotected in two ways: (a) by a purely chemical method, affording the dinucleoside diphosphates in a circa one to one mixture of 2'- and 3'- isomers, 10b-13b and 10a-13a, respectively, and (b) by a mixed chemical-enzymatical approach which gives the pure 3'-phosphates (10a-13a).     

The synthesis and immunosuppressive activities of steroid-urotoxin linkers

The urotoxins (Glu-Asp-Gly-OH, His-Gly-Glu-OH, His-Gly-Lys-OH, and His-Gly-Lys-NHNH(2)) were introduced into the convenient sites of hydrocortisone and prednisolone via the amidation or condensation reactions to form the corresponding linkers 7a-d, 8a-d, 9a,b, and 10a,b in acceptable yields. The bioassays such as prolongation of heterotopic transplanted cardiac tissue survival in vivo, inhibitory effects on phagocytosis of mouse peritoneal macrophages and concanavalin (ConA) or lipopolysaccharide (LPS) induced proliferation of mouse spleen lymphocytes in vitro show that at the comparable concentrations the immunosuppressive activities of the steroid-urotoxin linkers 7a-d, 8a-d, 9a,b, and 10a,b were higher than that of hydrocortisone, prednisolone, and the urotoxins alone, as well as significantly higher than that of the mixture of hydrocortisone and urotoxins or prednisolone and urotoxins. The so-called 'permissive action' may be responsible for the enhancement of the mentioned bioactivities of the steroid-urotoxin linkers 7a-d, 8a-d, 9a,b, and 10a,b.     

Syntheses of cyclic prodrugs of RGD peptidomimetics with various macrocyclic ring sizes: evaluation of physicochemical, transport and antithrombic properties.

The objective of this work was to synthesize cyclic prodrugs 1a-d of RGD peptidomimetics 2a-d with various ring sizes (n[CH2] = 1, 3, 5 and 7) and to evaluate the effect of ring size on their transport, physicochemical, enzymatic stability, and antithrombic properties. The syntheses of cyclic prodrugs 1a-d were achieved by converging two key intermediates, Boc-Phe-O-CH2-OCO-OpNP (5) and H2N-(CH2)n-CO-Asp(OBzl)-OTce (8a-d), to give linear precursors Boc-Phe-O-CH2-OCO-HN-(CH2)n-CO-Asp(OBzl)-OTce (9a-d). The N- and C-terminus protecting groups were removed from 9a-d to give 10a-d. Linear precursors 10a-d were cyclized, and the remaining Bzl-protecting group was removed to produce cyclic prodrugs 1a-d in around 20% overall yield. The linear RGD peptidomimetics (2a-d) were synthesized using standard Boc-amino acid chemistry by solution-phase method. Increasing the ring size by adding methylene groups also increases the hydrophobicity of the cyclic prodrugs and parent RGD peptidomimetics. The transport properties of cyclic prodrugs 1c and 1d were 2.6- and 4.4-fold better than those of parent compounds 2c and 2d, respectively. These results suggest that increasing the hydrophobicity of the cyclic prodrugs and parent RGD peptidomimetics enhanced their transport properties. The hydrodynamic radii of the cyclic prodrugs were also smaller than those of their respective parent compounds, suggesting that the change in size may contribute to their transport properties. The chemical stability of the cyclic prodrugs was affected by the ring size, and the cyclic prodrug with the larger ring size (i.e. 1d) was more stable than the smaller one (i.e. 1a). All the cyclic prodrugs were more stable at pH 4 than at pH 7 and 10. Prodrug-to-drug conversion could be induced by isolated esterase as well as esterase found in human plasma. An increase in the length of methylene group (n[CH2] = 1, 3, 5, 7) enhanced the antithrombic activity of the prodrugs and the parent compounds. In summary, the ring size of cyclic prodrugs affected their transport, physicochemical, and antithrombic properties.     

Synthesis of furanone-based natural product analogues with quorum sensing antagonist activity

The synthesis of 5- and 3-(1'-hydroxyalkyl)-substituted 5H-furan-2-ones 4a-d and 8a-d as well as 5-alkylidene-5H-furan-2-ones 5a-d is described. A study of the structure-activity relationship of these furanone-based natural product analogues towards two different quorum sensing systems is reported. Although the synthesized compounds are not as potent quorum sensing inhibitors as some natural counterparts and a synthetic analogue hereof, interesting structure-activity relationships are seen.     

Acyclic analogs of dideoxydidehydronucleosides

A new type of acyclic nucleoside analogs is proposed, containing C5 hydroxyalkyl fragments, where the distance between 5'-hydroxyl group and the heterocyclic moiety corresponds to that in dideoxydidehydronucleosides (as confirmed by computer modelling). Condensation between 5-0-acetyl-1-bromo-2-pentene and persilylated heterocyclic bases (pyrimidines and guanine) or adenine sodium salt gives rise to the acyclic nucleosides (5a-d, 6a-d) with the yields ranging from 40% up to 85%. Deprotection by NH3/MeOH results in the desired nucleosides (1a-d, 2a-d) formation.     

Synthesis and biological evaluation of (R)-N-(diarylmethylthio/sulfinyl)ethyl/propyl-piperidine-3-carboxylic acid hydrochlorides as novel GABA uptake inhibitors

A series of new (R)-1-(2-diarylmethylthio/sulfinyl)ethyl-piperidine-3-carboxylic acid hydrochlorides 5a-d/6a-d and (R)-1-(3-diarylmethylthio)propyl-piperidine-3-carboxylic acid hydrochlorides 5'a-d were synthesized and evaluated as gamma-aminobutyric acid uptake inhibitors through cultured cell lines expressing mouse GAT1. Biological screening results demonstrated that the compounds 6a-d with diarylmethylsulfinyl ethyl side chain show more potent GAT1 inhibitory activities than 5a-d/5'a-d with diarylmethylthio ethyl/propyl moieties. Some of them, such as 6a, exhibited excellent inhibitions of [(3)H]-GABA uptake in cultured cells, which is 496-fold higher than (R)-nipecotic acid and 11.5 times less than tiagabine. The synthesis and structure-activity relationships are discussed.     

Reactions of Some 2,3-Anhydro Pyrimidine Nucleosides with Dilithium Tetrahalocuprates

Abstract

The reaction of 1-(2,3-anhydro-5-0-trityl-β-D-lyxofuranosyl)-2-0-methyluracil (2a) and its thymine analogue (2b) with dilithium tetrahalocuprates (Li₂CuX₄) revealed an excellent to perfect regioselectivity, yielding 2,2′-anhydro-3′-halonucleosides (3a-d), while the same reactions with 2,3-anhdro uracil and thymine nucleosides (5a,b) gave arabinosyl (6a-d) and xylosyl halohydrins (7a-d) with respective product ratios of 7:3 to 8:2 which were estimated after mesylation to 8a-d and 9a-d.     

Regioselective halogenation of some 2,3-anhydro pyrimidine nucleosides with dilithium tetrahalocuprates.

The reaction of 1-(2,3-anhydro-5-O-trityl-beta-D-lyxofuranosyl)-2-O-methyluracil (1a) and its thymine analogue (1b) with dilithium tetrahalocuprate (Li2CuX4) revealed excellent to perfect regioselectivity, yielding 2,2'-anhydro-3'-halonucleosides (2a-d), while the same reactions with 2,3-anhydro uracil and thymine nucleosides (4a,b) gave arabinosyl (5a-d) and xylosyl halohydrins (6a-d) with the respective product ratio of 7:3 to 8:2. compounds 5 and 6 were isolated as the 2-O-(7) and 3- O-mesyl derivatives (8).     

Activation of antibacterial prodrugs by peptide deformylase

5'-Dipeptidyl derivatives of 5-fluorodeoxyuridine (FdU) (1a-d) were synthesized. These compounds are biologically inactive but can be activated by peptide deformylase, which removes the N-terminal formyl group of the dipeptide, to release the active drug FdU via an intramolecular cyclization reaction. Because the deformylase is ubiquitous among bacteria but absent in mammalian cells, 1a-d provide a novel class of potential antibacterial agents.     

Studies on the synthesis of neamine-dinucleosides and neamine-PNA conjugates and their interaction with RNA

Two types of neamine derivatives, neamine-dinucleotide conjugates 8a-g and neamine-PNA conjugates 12a-c and 14a-d, were synthesized. Compound 8a-g were synthesized by the condensation of azido-neamine with dinucleotide-5'-carboxylic acids, followed by reduction and deprotection. Compound 12a-c and 14a-d were synthesized by the similar strategy. The binding affinities of conjugates 8a-g, 12a-c, and 14a-d towards 16S RNA, 18S RNA, and TAR RNA were evaluated by SPR. It indicates that conjugates 12a-c and 14a-d interact with 16S, 18S RNA at the same level as that of neamine, 14a and 14d show about twofold binding affinities to TAR RNA compared to that of neamine. However, the neamine-dinucleotide conjugates 8a-g exhibit very weak binding affinities to 16S, 18S, and TAR RNA, computer modelling results that negative-negative electrostatic repulsion of phosphate group in compound 8a-g and RNA leads to a sharp decrease of the binding affinities compared with that of neamine, neamine-nucleoside and neamine-PNA conjugates.     

4-[(8-Alkyl-8-azabicyclo[3.2.1]octyl-3-yl)-3-arylanilino]-N,N-diethylbenzamides: high affinity, selective ligands for the delta opioid receptor illustrate factors important to antagonist activity

The tropane derived compounds, 4-[(8-alkyl-8-azabicyclo[3.2.1]octyl-3-yl)-3-arylanilino]-N,N-d iethylbenzamides (5a-d), were synthesized and found to have high affinity and selectivity for the delta receptor. Compounds 5a-d are structurally similar to the full agonist (-)-RTI-5989-54 (3); yet, efficacy studies for compounds in this series (5a-d) reveal greatly diminished agonist activity as well as antagonism not found in piperidine-based compounds like 3.     

Solid phase synthesis of quinolones.

Solid phase syntheses of ethyl 6-carboxyquinol-4(1H-)-one-3-carboxylate (5) and N-substituted 6-carboxyquinol-4(1H)-one-3-carboxamides 7a-d have been described. Antifilarial in vitro activities of 5,7a-d against Brugia malayi have also been delineated.     

Synthesis and biology of 3'-N-acyl-N-debenzoylpaclitaxel analogues.

The, 3'-N-acyl-N-debenzoylpaclitaxel analogues 1a-d were synthesized and evaluated on biological systems. Some of the analogues 1a-d exhibited higher cytotoxicities (up to 20-fold) and stronger abilities to induce apoptosis than paclitaxel. In an in vivo experiment against i.p. implanted B16 melanoma, the most cytotoxic compound 1b in vitro caused tumor growth inhibition more than paclitaxel.     

Novel N-(3-carboxyl-9-benzyl-carboline-1-yl)ethylamino acids: synthesis, anti-proliferation activity and two-step-course of intercalation with calf thymus DNA

To explore the intercalating mechanism of -carbolines, four novel N-(3-carboxyl-9-benzyl-carboline-1-yl)ethylamino acids [-phenylalanine (6a), -alanine (6b), -isoleucine (6c) and -glycine (6d)] were prepared here. Their in vitro anticancer activities were examined by their anti-proliferation for 5 human carcinoma cell lines. The average IC50s against 5 human carcinoma cell lines are 53.54 microM, 118.77 microM, 147.34 microM and greater than 291.63 microM for 6a, 6b, 6c and 6d, respectively. The DNA intercalating mechanism of 6a-d was approved by the comparison of the parameters and signals of UV, CD and fluorescence spectra of calf thymus DNA (CT DNA) alone and the CT DNA/6a-d system. Using fluorescence titration based kinetic analysis a two-step-course consisting of stacking and intercalating was described and the stacking was considered as the key step to the CT DNA intercalating mechanism of 6a-d. Using fluorescence titration based thermomechanical analysis, the stacking complexes of 6a-d with CT DNA were described to be formed spontaneously and to be stabilized predominantly by their hydrophobic interactions. The intercalation itself goes very fast and only has limited contribution to their anticancer activities.     

Unique spirocyclopiperazinium salt. Part 2: synthesis and structure-activity relationship of dispirocyclopiperazinium salts as analgesics

Three series of spirocyclopiperazinium derivatives 5a-d, 6a-f and 17a-d were synthesized and evaluated for their in vivo analgesic activities. Compounds 5a, 17a and 17b exhibited excellent analgesic activity. Two important structure-activity relationships were observed from this study: (1) the quaternary ammonium functionality is a critical pharmacophore for analgesic activity; (2) it is important to adjust the lipophilic property of compounds to improve analgesic activity.