Thiosugar Nucleosides. Synthesis and Biological Activity of 1,3,4‐Thiadiazole,Thiazoline and Thiourea Derivatives of 5‐Thio‐d‐Glucose

New acylated 5‐thio‐β‐d‐glucopyranosylimino‐disusbstituted 1,3,4‐thiadiazols 8, and 11 were prepared, via spontaneous rearrangements, by cycloaddition of the glycosyl isothiocyanate 2 with the reactive intermediates 1‐aza‐2‐azoniaallene hexachloroantimonates 4 and 6, respectively. Reaction of 2 with aminoacetone or chloroethylamine afforded the acylated 5‐thio‐β‐d‐glucopyranosyl‐4‐imidazoline‐2‐thione nucleoside 16 and glucopyranosylamino‐2‐thiazoline derivative 18, respectively. Deblocking of 8, 11, 17 and 19 furnished the free nucleoside analogues 9, 12, 18 and 20, respectively. Analogously, treatment of 2 with chloroethylamine in the 1:2 ratio afforded the thioureylendisaccharide 21. No in vitro antiviral activity against HIV‐1, HIV‐2, human cytomegallovirus (HMCV), has been found for the new synthesized compounds.     

Synthesis of acyclic 6,7-dihaloquinolone nucleoside analogues as potential antibacterial and antiviral agents

Reaction of the quinolone carboxylic acids 1 and 2 with (2-acetoxyethoxy)methyl chloride 3 in the presence of n-Bu4NI afforded the N-alkylated products 4 and 6, which could be deblocked to the free nucleoside analogues 5 and 7, respectively. The alkylated quinolone carboxylic acids 9 and 10 were obtained by condensation of I and 2 with 1,4-dichlorobut-2-ene 8 in the presence of NaH. Hydrolysis of 9 gave the alcohol 11. Similar treatment of 1 with 8 in the presence of K2CO3 at relatively high temperature furnished 12. Prolonged heating of the ester 13 with 8 in NaH/DMF afforded the conjugated-diene 15. Treatment of 1 and 2 with dimethyl acetylenedicarboxylate 16 furnished the pyrano[4,3-b]quinolones 17 and 18, respectively. Antibacterial and antiviral evaluations of the new products are reported.     

Quinolone Nucleosides: 6,7-Dihalo-N-β- and α-Glycosyl-l 4-dihydro-4-oxo-quinoline-3-carboxylic Acids and Derivatives. Synthesis,Antimicrobial and Antiviral Activity

Abstract

Reaction of the silylated 6,7-dihaloquinoline bases 10–12 with l-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (13) gave ethyl 7-chloro-6-flouro-l,4-dihydro-4-oxo-1 -(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)quinoline-3-carboxylate (14) and the free acids 15 and 16, respectively, which led on deblocking of the sugar moiety to the free nucleosides 17, 18 and 20, respectively. Treatment of 14 with methanolic ammonia afforded the amide derivative 19. Ribosylation of 11 with l,2-di-O-acetyl-3-azido-3-deoxy-5-p-toluoyl-β-D-ribofuranose (21) afforded the azido nucleoside 22, which was again converted into the free nucleoside 23. Analogously, reaction of 11 with the chloro deoxyribose derivative 24 led to a mixture of α /β (2:1) anomers of 25. Deblocking and recrystallization of the product gave mainly the α-anomer 26. Compounds 17–19, 23 and 26 were evaluated against Escherichia coli and found inactive. Compound 16–18 and 22 were inactive aganist HIV-1 (III B) and HIV-2 (ROD) induced cytopathicity in human MT-4 lymphocyte cells.     

Synthesis of N-substituted 1-amino-2,3-dihydro-1H-imidazole-2-thione-N-nucleosides and S-glycosylated derivatives

Fusion of the N-substituted 1-amino-2,3-dihydro-1H-imidazole-2-thiones 1-4 with the peracylated ribose 5 in the presence of iodine afforded the N-nucleosides 6-9 in moderate yields. Deblocking with NaOMe/MeOH gave the free nucleosides 10-13. Alternatively, silylation of 4 followed by ribosylation with 5 in the presence of TMSOTf as catalyst afforded 9 in moderate yield. Ribosylation of 4 with the chlorodeoxyribose derivative 15 as well as 5 in the presence of NaH in DMF afforded the thioglycosides 16 and 18, respectively. Deblocking of 16 and 18 with NaOMe/MeOH gave the free S-thioglycosides 17 and 19, respectively. Thermal rearrangement of 19 at high temperature in the presence of iodine furnished 13 in low yield. The new free nucleosides and thioglycosides were inactive against HIV-1 and HIV-2 induced cytopathicity in human MT-4 lymphocyte cells.     

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.     

Nucleosides 7(9): synthesis, structure, and biological activity of new 6-arylidenamino-2-thio- and 2-benzylthiopyrimidine N-nucleosides

The condensation of 6-amino-2-thioxo-2,3-dihydro-1H-pyrimidine-4-one [compound (1)] with aromatic aldehydes (2) afforded azomethine derivatives (3). The formed azomethines underwent glycosidation with α-acetobromoglucose (4) to form the corresponding pyrimidine N-glycosides (6) and not S-glycosides (5). The interaction of (3) with 1-O-acetyl-2, 3, 5-tri-O-benzoyl-β-D-ribofuranose (8) afforded the corresponding pyrimidine N-riboside (10) and not S-riboside (9). Deacetylation and debenzoylation of each of (6) and (10) by using methanolic sodium methoxide afforded the corresponding free N-nucleosides (7) and (11), respectively. Next, the reaction of 2-benzylthio-6-benzylidenaminouracil (13) with (4) and (8) did not yield the corresponding protected N-nucleosides (14) and (17), whereas it afforded (15) and (18), respectively. The latter compounds (15) and (18) were stirred in methanolic sodium methoxide to yield the corresponding free N-nucleosides (16) and (19), respectively. The structures of products have been elucidated and reported and also some of the products were screened for their antimicrobial activity. Graphical Abstract:     

New sulphonamide and carboxamide derivatives of acyclic C-nucleosides of triazolo-thiadiazole and the thiadiazine analogues. Synthesis, anti-HIV, and antitumor activities. Part 2

A new series of acyclic C-nucleosides 1',2'-O-isopropylidene-D-ribo-tetritol-1-yl)[1,2,4] triazolo[3,4-b][1,3,4]thiadiazoles bearing arylsulfonamide (5-8) and arylcarboxamide (9-12) residues have been synthesized under microwave irradiation. Thiadiazines 13-15 have been analogously prepared, and upon acid hydrolysis, afforded the free nucleosides 16-18. The new synthesized compounds were assayed against HIV-1 and HIV-2 in MT-4 cells. Compound 7 was also screened against a panel of tumor cell lines consisting of CD4 human T-cells.     

Synthesis and antiviral activity of 1,5- and 1,3-dialkyl-1,2,4-triazole C-nucleosides derived from 1-(chloroalkyl)-1-aza-2-azoniaallene salts.

Reactions of alpha,alpha'-dichloroazo compounds 2 with SbCl5 gave 1-(chloroalkyl)-1-aza-2-azoniaallene salts 3 as reactive intermediates. Cycloadditions of 3 with the ribofuranosyl cyanide 4 afforded the beta-D-ribofuranosyl-1,2,4-triazolium salts 5, which rearranged spontaneously to salts 6. Hydrolysis of 6 gave the 1,2,4-triazole C-nucleosides 7, which yielded the free nucleosides 8 after deblocking. Analogously, 12 was prepared from the cycloaddition of 4 with the alpha-chloroazo compound 10 in the presence of SbCl5. Deblocking of 12 with sodium methoxide afforded 13. Compounds 8a,b,e,f and 13 were tested against HIV-1, HIV-2, HSV-1 and HSV-2 and were found to be inactive.     

Synthesis, X-ray crystal structural study, antiviral and cytostatic evaluations of the novel unsaturated acyclic and epoxide nucleoside analogues

A series of the novel purine and pyrimidine nucleoside analogues were synthesised in which the sugar moiety was replaced by the 4-amino-2-butenyl (2-6 and 10-18) and oxiranyl (8 and 20) spacer. The Z- (2-6) and E-isomers (10-18) of unsaturated acyclic nucleoside analogues were synthesized by condensation of 2- and 6-substituted purine and 5-substituted uracil bases with Z- (1) or E-phthalimide (9) precursors. The oxiranyl nucleoside analogues (8 and 20) were obtained by epoxidation of 1 and 9 with m-chloroperoxybenzoic acid and subsequent coupling with adenine. The new compounds were evaluated for their antiviral and antitumor cell activities. Among the olefinic nucleoside analogues, Z-isomer of adenine containing 4-amino-2-butenyl side chain (6) exhibited the best cytostatic activities, particularly against colon carcinoma (SW 620, IC50 = 26 microM). Its E-isomer 15 did not show any antiproliferative activity against malignant tumor cell lines, except for a slight inhibition of colon carcinoma (SW 620, IC50 = 56.5 microM) cells. In general, Z-isomers showed better cytostatic activities than the corresponding E-isomers. (Z)-4-Amino-2-butenyl-adenine nucleoside analogue 6 showed albeit modest but selective activity against HIV-1 (EC50 = 4.83 microg mL(-1)).     

Etoposide: a new approach to the synthesis of 4-O-(2-amino-2-deoxy-4,6-O-ethylidene-beta-D-glucopyranosyl)-4'-O- demethyl-4-epipodophyllotoxin

Synthesis of 3-O-acetyl-2-benzyloxycarbonylamino-2-deoxy-4,6-O-ethylidene- alpha-(7 alpha) and-beta-D-glucopyranose (7 beta) and their 3-O-chloroacetyl analogues (11 alpha and 11 beta) are described. Condensation (BF3-etherate, ethyl acetate, -20 degrees) of 7 alpha with 4'-O-benzyloxycarbonyl-4'-O-demethyl-4-epipodophyllotoxin (8) afforded mainly the beta-glycoside 9 beta (alpha, beta-ratio 1:9). Condensation of 11 alpha beta with 8 or the 4'-O-chloroacetyl analogue 13 gave mainly the 4-O-(2-benzyloxycarbonylamino-3-O-chloroacetyl-2-deoxy-4,6-O-ethyl idene-beta-D- glucopyranosyl)-epipodophyllotoxin 12 beta or 15 beta. Glycosidation of podophyllotoxin (14) with 11 alpha beta (during which the aglycon epimerized at C-4 under the action of BF3-etherate) afforded alpha- (16 alpha) and beta-glycoside (16 beta) in the ratio 1:5. Removal of the chloroacetyl groups from 12 beta, its alpha analogue 12 alpha, and 15 beta gave the 4-O-(2-benzyloxycarbonylamino-2-deoxy-4,6-O-ethylidene-alpha-(17 alpha) and -beta-D-glucopyranosyl)-4'-O-demethyl-epipodophyllotoxins (17 beta and 20 beta), respectively. Hydrogenolysis of the benzyloxycarbonyl groups then gave 4-O-(2-amino-2-deoxy-4,6-O-ethylidene-alpha- (18 alpha) and -beta-D-glucopyranosyl)-4'-O-demethyl-4-epipodophyllotoxin (18 beta). Reductive alkylation of 18 beta and 18 alpha afforded the 2"-deoxy-2"-dimethylamino-etoposide 3 and its alpha analogue 19 alpha.     

New Sulphonamide and Carboxamide Derivatives of Acyclic C-Nucleosides of Triazolo-Thiadiazole and the Thiadiazine Analogues. Synthesis,Anti-HIV,and Antitumor Activities. Part 2

A new series of acyclic C-nucleosides 1′,2′-O-isopropylidene-D-ribo-tetritol-1-yl)[1,2,4] triazolo[3,4-b][1,3,4]thiadiazoles bearing arylsulfonamide (5–8) and arylcarboxamide (9–12) residues have been synthesized under microwave irradiation. Thiadiazines 13–15 have been analogously prepared, and upon acid hydrolysis, afforded the free nucleosides 16–18. The new synthesized compounds were assayed against HIV-1 and HIV-2 in MT-4 cells. Compound 7 was also screened against a panel of tumor cell lines consisting of CD4 human T-cells.     

Preparation of 8,5'-O-cycloadenosine derivatives by reaction of 2',3'-O-isopropylideneadenosine with phenyl chloroformate or p-toluyl chloride

Reaction of 2',3'-O-isopropylideneadenosine with p-toluyl chloride in a mixture of methylene chloride and triethylamine afforded 2',3'-O-isopropylidene-N,N,5'-O-tri-p-toluyladenosine (8)(30%), 8,5'-O-cycloadenosine derivatives 9 (34%) and 10 (11%), and a cyanoimidazole nucleoside 11 (12%).     

Enantiomeric forms of 9-(5-deoxy-beta-erythro-pent-4-enofuranosyl)adenine and a new preparation of 5-deoxy-D-lyxose.

Methyl 5-deoxy-5-iodo-2,3-O-isopropylidene-beta-D-ribofuranoside (3) was obtained in three steps from D-ribose. Exchange of the isopropylidene group for benzoate groups and acetolysis gave 1-O-acetyl-2,3-di-O-benzoyl-5-deoxy-5-iodo-D-ribofuranose which was coupled with 6-benzamidochloromercuripurine by the titanium tetrachloride method to afford the blocked nucleoside. Treatment with 1,5-diazabicyclo[5.4.0]undec-5-ene in N,N-dimethylformamide and removal of the blocking groups have 9-(5-deoxy-beta-D-erythro-pent-4-enofuranosyl)adenine (9). A similar route starting from methyl 5-deoxy-5-iodo-2,3-O-isopropylidene-alpha-D-lyxofuranoside (14) afforded the enantiomeric nucleoside, 9-(5-deoxy-beta-L-erythro-pent-4-enofuranosyl)adenine (20). Methyl 2,3-O-isopropylidene-alpha-D-mannofuranoside was treated with sodium periodate and then with sodium borohydride to give methyl 2,3-O-isopropylidene-alpha-D-lyxofuranoside (11). Acid hydrolysis afforded D-lyxose. Tosylation of 11 gave methyl 2,3-O-isopropylidene-5-O-p-tolylsulfonyl-alpha dp-lyxofuranoside (12) which was converted into 14 with sodium iodide in acetone. Reduction of 12 gave methyl 5-deoxy-2,3-O-isopropylidene-alpha-D-lyxofuranoside which was hydrolyzed to give 5-deoxy-D-lyxose.     

Synthesis of 18-hydroxy-19-norcorticosterone and 18-deoxy-19-noraldosterone. Structure determination of related 19-nor steroids by means of 2-D 1H nmr

The compounds named in the title have been synthesized from the di-(ethylene ketal) of 21-hydroxy-3,20-dioxo-19-norpregn-5-ene-18, 11 beta-lactone and its 5(10)-ene isomer. Reduction of this mixture 1 with sodium aluminum bis-(methoxyethoxy)hydride furnished the 11 beta, 18, 21-triol 2a. Conversion to the 18,21-diacetate 2b, followed by deketalization to the free dione 3 and hydrolysis, afforded 18-hydroxy-19-norcorticosterone 4a which, in the solid state and probably in solution, has the 18,20-hemiacetal structure. Periodate oxidation of 4a gave 11 beta-hydroxy-3-oxo-19-norandrost-4-ene-17 beta, 18-carbolactone 5a, and acid treatment of 4a or its precursor 2a yielded 18-deoxy-19-noraldosterone 6a. The structure of 5a was confirmed by mass spectrometry and 1H nmr, and compared with that of its C-19 methyl homolog 5b and 19-noraldosterone-gamma-etiolactone 8. In particular, 2-D nmr COSY 45 experiments, affording full 1H line assignments, have rigorously established the "natural" beta (axial) configuration of the C-10 hydrogen in the 19-nor lactones 5a and 8, and therefore also in the related 4a, 6a and 19-noraldosterone 7.     

Role of Naturally Occurring Basic Amino Acid Substitutions in the Human Immunodeficiency Virus Type 1 Subtype E Envelope V3 Loop on Viral Coreceptor Usage and Cell Tropism

To assess the role of naturally occurring basic amino acid substitutions in the V3 loop of human immunodeficiency virus type 1 (HIV-1) subtype E on viral coreceptor usage and cell tropism, we have constructed a panel of chimeric viruses with mutant V3 loops of HIV-1 subtype E in the genetic background of HIV-1LAI. The arginine substitutions naturally occurring at positions 8, 11, and 18 of the V3 loop in an HIV-1 subtype E X4 strain were systematically introduced into that of an R5 strain to generate a series of V3 loop mutant chimera. These chimeric viruses were employed in virus infectivity assays using HOS-CD4 cells expressing either CCR5 or CXCR4, peripheral blood mononuclear cells, T-cell lines, or macrophages. The arginine substitution at position 11 of the V3 loop uniformly caused the loss of infectivity in HOS-CD4-CCR5 cells, indicating that position 11 is critical for utilization of CCR5. CXCR4 usage was conferred by a minimum of two arginine substitutions, regardless of combination, whereas arginine substitutions at position 8 and 11 were required for T-cell line tropism. Nonetheless, macrophage tropism was not conferred by the V3 loop of subtype E R5 strain per se. We found that the specific combinations of amino acid changes in HIV-1 subtype E env V3 loop are critical for determining viral coreceptor usage and cell tropism. However, the ability to infect HOS-CD4 cells through either CXCR4 or CCR5 is not necessarily correlated with T-cell or macrophage tropism, suggesting that cellular tropism is not dictated solely by viral coreceptor utilization.     

Synthesis of a heptasaccharide fragment of the O-deacetylated GXM of C. neoformans serotype C

Beta-D-Xylp-(1-->2)-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->2)][beta-D-Xylp-(1-->4)]-alpha-D-Manp-(1-->3)-[beta-D-Xylp-(1-->4)]-alpha-D-Manp, the fragment of the exopolysaccharide from Cryptococcus neoformans serovar C, was synthesized as its methyl glycoside. Thus, chloroacetylation of allyl 3-O-acetyl-4,6-O-benzylidene-alpha-D-mannopyranoside (1) followed by debenzylidenation and selective 6-O-benzoylation afforded allyl 2-O-chloroacetyl-3-O-acetyl-6-O-benzoyl-alpha-D-mannopyranoside (4). Glycosylation of 4 with 2,3,4-tri-O-benzoyl-D-xylopyranosyl trichloroacetimidate (5) furnished the beta-(1-->4)-linked disaccharide 6. Dechloroacetylation gave the disaccharide acceptor 7 and subsequent coupling with 5 produced the trisaccharide 8. Deacetylation of 8 gave the trisaccharide acceptor 9 and subsequent coupling with a disaccharide 10 produced the pentasaccharide 11. Reiteration of deallylation and trichloroacetimidate formation from 11 yielded the pentasaccharide donor 12. Coupling of a disaccharide acceptor 13 with 12 afforded the heptasaccharide 14. Subsequent deprotection gave the heptaoside 16, while selective 2-O-deacetylation of 14 gave the heptasaccharide acceptor 15. Condensation of 15 with glucopyranosyluronate imidate 17 did not yield the expected octaoside, instead, an orthoester product 18 was obtained. Rearrangement of 18 did not give the target octaoside; but produced 15. Meanwhile, there was no reaction between 15 and the glycosyl bromide donor 19.     

Novel synthesis of seco type of acyclo C-nucleosides of 1,2,4-triazole and 1,2,4-triazol

The seco C-nucleosides 3-(1,2,3,4,5-penta-O-acetyl-D-gluco- and D-galacto-pentitol-1-yl)-1H-1,2,4-triazoles (8 and 9) were obtained in a one pot by deamination and dethiolation of 4-amino-3-(D-gluco- and D-galacto-pentitol-1-yl)-5-mercapto-1,2,4-triazoles (1 and 2), respectively, using sodium nitrite in orthophosphoric acid and subsequent acetylation. Condensation of 1, 2, and 4-amino-3-(D-glycero-D-gulo-hexitol-1-yl)-5-mercapto-1,2,4-triazole (12) with phenacylbromide (11) afforded the corresponding 3-(D-gluco-, D-galactopentitol-1-yl) and 3-(D-glycero-D-gulo-hexitol-1-yl)-6-phenyl-7H-1,2,4-triazolo[3,4-b][1,3,4] thiadiazines (15, 16, and 17). Acetylation of 15-17 gave the penta- and hexa-O-acetyl derivatives 18-20, respectively. The structures were confirmed by using 1H, 13C, and 2D NMR spectra, DQFCOSY, HMQC, and HMBC experiments. The favored conformational structures were deduced from the vicinal coupling constants of the protons.     

Synthesis of novel 4'-cyclopropyl-5'-norcarbocyclic adenosine phosphonic acid analogues

Novel 4'-cyclopropyl-5'-norcarbocyclic adenosine phosphonic acid analogues were designed and racemically synthesized from propionaldehyde 5 through a de novo acyclic stereoselective route using triple Grignard addition and ring-closing metathesis (RCM) as key reactions. To improve cellular permeability and enhance the anti-HIV activity of this phosphonic acid, SATE phosphonodiester nucleoside prodrug 23 was prepared. The synthesized adenosine phosphonic acids analogues 17, 18, 19, 21, and 23 were subjected to antiviral screening against HIV-1. Compound 23 exhibits enhanced anti-HIV activity than its parent nucleoside phosphonic acid 18.