Synthesis and antiretrovirus properties of 5'-isocyano-5'-deoxythymidine, 5'-isocyano-2',5'-dideoxyuridine, 3'-azido-5'-isocyano-3',5'-dideoxythymidine, and 3'-azido-5'-isocyano-2',3',5'-trideoxyuridine

The 5'-azidonucleosides 3 and 4 were obtained by treating thymidine and 2'-deoxyuridine with TPP/DEAD/HN3. The 3'-O-silylated 5'-azido-5'-deoxythymidine 5 and the corresponding 2'-deoxyuridine derivative 6 were transformed to the formamides (7 and 8, respectively) and dehydrated to the protected 5'-isocyano derivatives 9 and 10; deblocking gave 5'-isocyano-5'-deoxythymidine (11) and 5'-isocyano-2',5'-dideoxyuridine (12). 2,3'-Anhydro-5'-formamido derivatives of thymidine and 2'-deoxyuridine (19 and 20, respectively) were prepared by three different ways. In the most direct synthesis 3 and 4 were transformed to the 2,3'-anhydro-5'- azidonucleosides 17 and 18 by using TPP/DEAD; following the reaction with TPP/HCO2COCH3 gave 19 and 20. Nucleophilic opening reaction with LiN3 yielded the 3'-azido-5'-formylamino derivatives 21 and 22. Dehydration to 3'-azido-5'-isocyano-3',5'-dideoxythymidine (23) and 3'-azido-5'-isocyano-2',3',5'-trideoxyuridine (24) was achieved with tosyl chloride/pyridine. In contrast with 3'-azido-3'-deoxythymidine, compounds 11, 12, 23, and 24 were devoid of any marked inhibitory effect against DNA and RNA viruses including human immunodeficiency virus type I (HIV).     

Reactive 5'-substituted 2',5'-dideoxyuridine derivatives as potential inhibitors of nucleotide biosynthesis

5'-(Bromoacetamido)-2',5'-dideoxyuridine (3) and derivatives (8, 10, 12, and 14) substituted at the 5-position with bromo, iodo, fluoro, and ethyl groups have been synthesized as potential inhibitors of enzymes that metabolize pyrimidine nucleosides. Also prepared were 2',5'-dideoxyuridine derivatives (4-6) substituted at the 5'-position with 2-bromopropionamido, iodoacetamido, and 4-(fluorosulfonyl)benzamido groups. Compounds 3, 5, 8, 12, and 14 were examined for effect on macromolecular synthesis in L1210 leukemia cells in culture and compared with 5'-(bromoacetamido)-5'-deoxythymidine (1, BAT), a compound with demonstrated cytotoxicity and activity in vivo against P388 murine leukemia. Compounds 3, 8, 12, and 14 inhibited DNA synthesis without significant inhibition of RNA synthesis, and protein synthesis was affected less than DNA synthesis. Compounds 3, 5, 6, 8, 10, 12, and 14 were cytotoxic to H.Ep.-2 and L1210 cells in culture, and 3, 5, 8, and 12 showed activity in the P388 mouse leukemia screen.     

Synthesis and antitumor and antiviral properties of 5-halo- and 5-(trifluoromethyl)-2'-deoxyuridine 3',5'-cyclic monophosphates and neutral triesters

The title diesters (11-15; halo substituents F, Cl, Br, I) were prepared by DCC-induced cyclization of the precursor 5'-monophosphate or direct halogenation of the 2'-deoxyuridine 3',5'-cyclic monophosphate. Antitumor activities of 11-15 in cell systems (L1210 and Raji/0) were compared to those of the corresponding nucleosides and 5'-monophosphates. Thus, the 5-F- and 5-CF3-2'-deoxyuridines proved to be highly active derivatives [ID50 values (microgram/mL) for L1210, 0.002 and 0.06, respectively], with the 5'-monophosphates showing comparable potencies. The corresponding 3',5'-cyclic monophosphate diesters were 20-30 times less potent but nonetheless highly cytostatic. All derivatives including 11-15 had greatly increased ID50 values for the thymidine kinase deficient (TK-) L1210 and Raji cells. The 3',5'-cyclic diesters (11-15) evidently are not efficient prodrug sources of the nucleoside 5'-monophosphates in TK- cells. They also proved to be 100- to 2000-fold less efficient inhibitors of L1210 thymidylate synthetase than were the 5'-monophosphates. The 5-substituted 2'-deoxyuridines and their 5'-monophosphates were potent inhibitors of herpes simplex virus (MIC50 mostly 0.07-10 micrograms/mL) and vaccinia virus (MIC50 0.07-0.2 microgram/mL), with antiviral activity decreasing in the order 5-I, 5-Br greater than 5-CF3 greater than 5-Cl greater than 5-F. The 3',5'-cyclic monophosphates (11-15) were for the most part 10- to 40-fold less active than the 5'-monophosphates in the virus assay systems (e.g., MIC50 for the 5-Br and 5-I derivatives ranged 1-20 micrograms/mL). By contrast 11-15 were considerably more potent inhibitors of vaccinia virus growth (MIC50 0.4-2 micrograms/mL). As the neutral 3',5'-cyclic methyl phosphate triesters (16-18), the 5-I and 5-Br compounds were less potent in antiviral and cytostatic agents than the 3',5'-cyclic diesters, while the 5-iodo benzyl triester was in several cases as active as the 3',5'-cyclic diester. The title compounds (11-15) appear to require extracellular hydrolysis to the nucleoside before functioning as antitumor or antiviral agents.     

Synthesis and antiviral activity of 5- and 5'-substituted thymidine analogs.

The 5'-O-p-tolylsulfonyl derivatives of 5-chloro-, 5-bromo-, and 5-iodo-2'-deoxyuridine were synthesized and converted into the corresponding 5-halo-5'-azido-2',5'-dideoxyuridines (5-7). Reduction of 5-chloro-5'-azido-2',5'-dideoxyuridine (5) afforded 5-chloro-5'-amino-2',5'-dideoxyuridine (10, ACIU); however, similar efforts to prepare 5-bromo-5'-amino-2',5'-dideoxyuridine (11) and 5-iodo-5'-amino-2',5'-dideoxyuridine (12) by reduction of the corresponding 5'-azido precursor resulted in the formation of 5'-amino-2',5'-dideoxyuridine (9). 5-Bromo-5'-amino-2',5'-dideoxyuridine (11, ABrU) and 5-iodo-5'-amino-2',5'-dideoxyuridine (12, AIU) were prepared by halogenation of the 5-mercuriacetate of 5'-amino-2',5'-dideoxyuridine. The 5'-amino-2',5'-dideoxy analogs of 5-methyl-, 5-chloro-, 5-bromo-, and 5-iodo-2'-deoxyuridine possess antiviral activity against herpes simplex virus but exhibit no inhibitory activity against sarcoma 180 (murine) or Vero (monkey) cells in culture.     

Molecular structure of the dihydropyridazinone cardiotonic 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-pyridazinyl)- 2H-indol-2-one, a potent inhibitor of cyclic AMP phosphodiesterase

The cardiotonic 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-3- pyridazinyl)-2H-indol-2-one (1, LY195115) is a potent, competitive inhibitor (Ki = 80 nM) of sarcoplasmic reticulum derived phosphodiesterase (SR-PDE). Moreover, the compound is a potent positive inotrope both in vitro and in vivo. To assist further cardiotonic drug-design studies, we have mapped the three-dimensional structure of 1 using X-ray crystallography. From a global viewpoint, this drug was essentially planar, but two small regions of nonplanarity were apparent. These involved the geminal methyl substituents in the indol-2-one moiety and the C5' methylene unit of the dihydropyridazinone ring. Because of our previous studies involving the bipyridine cardiotonics amrinone and milrinone, the conformational relationship between the plane of the phenyl ring and the horizontal symmetry plane defined by N2', C3', and C4' of 1 was of particular interest. The C6-C5-C3'-C4' dihedral angle was -2.7 degrees, whereas the C6-C5-C3'-N2' dihedral angle was 174.6 degrees. Therefore the two rings maintain a high degree of coplanarity. Compound 4, the congener of 1 possessing a completely unsaturated pyridazinone ring was also studied. In terms of inotropic activity, this compound, devoid of any puckering in the pyridazinone moiety, was equipotent with 1. Methyl substitution at the 4-position of the dihydropyridazinone and pyridazinone rings provided disparate results. Compound 2, the 4-methyl analogue of 1, was 2-fold more potent than 1, and the methyl substituent probably caused only minor perturbations in overall molecular topology. However 5, the 4-methyl analogue of the pyridazinone 4, was 4.4-fold less active than 4, perhaps as a result of methyl-induced molecular nonplanarity.     

Catabolic disposition of 3'-azido-2',3'-dideoxyuridine in hepatocytes with evidence of azido reduction being a general catabolic pathway of 3'-azido-2',3'-dideoxynucleosides.

3'-Azido-2',3'-dideoxyuridine (AzddU, CS-87) is a potent inhibitor of human immunodeficiency virus replication in vitro with low bone marrow toxicity. Although AzddU is currently being evaluated in clinical trials, its catabolic disposition is unknown. Pharmacokinetic studies in rhesus monkeys have demonstrated that a 5'-O-glucuronide is excreted in urine. The present study examined the catabolic disposition of AzddU is isolated rat hepatocytes, a model for the study at the cellular level of biosynthetic, catabolic and transport phenomena in the liver. Following exposure of cells to 10 microM [3H]AzddU, low intracellular levels of two catabolites, identified as 3'-azido-2',3'-dideoxy-5'-beta-D-glucopyranosyluridine (GAzddU) and 3'-amino-2',3'-dideoxyuridine (AMddU), were detected. Studies using rat microsomes demonstrated that GAzddU formation was only detected in the presence of uridine 5'-diphosphoglucuronic acid, and that the rate of AMddU formation increased significantly in the presence of NADPH. Under similar conditions, reduction of the 3'-azido function was also demonstrated herein with 3'-azido-2',3'-dideoxycytidine (AzddC), 3'-azido-2',3'-dideoxy-5-methylcytidine (AzddMeC) and 3'-azido-2',3'-dideoxyguanine (AzddG), suggesting that enzymatic reduction to a 3'-amino derivative is a general catabolic pathway of 3'-azido-2',3'-dideoxynucleosides at the hepatic site.     

Synthesis and antiviral activity of several 2,5'-anhydro analogues of 3'-azido-3'-deoxythymidine, 3'-azido-2',3'-dideoxyuridine, 3'-azido-2',3'-dideoxy-5-halouridines, and 3'-deoxythymidine against human immunodeficiency virus and Rauscher-murine leukemia virus

Several 2,5'-anhydro analogues of 3'-azido-3'-deoxythymidine (AZT), 3'-azido-2'3'-dideoxyuridine (AZU), 3'-azido-2'3'-dideoxy-5-bromouridine, 3'-azido-2',3'-dideoxy-5-iodouridine, and 3'-deoxythymidine and the 3'-azido derivative of 5-methyl-2'-deoxyisocytidine have been synthesized for evaluation as potential anti-HIV (human immunodeficiency virus) agents. These 2,5'-anhydro derivatives, compounds 13-17, demonstrated significant anti-HIV-1 activity with IC50 values of 0.56, 4.95, 26.5, 27.1, and 48 microM, respectively. Compared to that of the parent compounds AZT and AZU, the respective 2,5'-anhydro analogues, compounds 13 and 14, were somewhat less active. Whereas AZT was cytotoxic with a TCID50 of 29 microM, the toxicity of the 2,5'-anhydro derivative of AZT, compound 13, was reduced considerably to a TCID50 value of greater than 100 microM. The 2,5'-anhydro analogue of 5-methyl-2'-deoxyisocytidine also demonstrated anti-HIV-1 activity with an IC50 value of 12 microM. These compounds were also evaluated against Rauscher-Murine leukemia virus (R-MuLV) in cell culture. Among them, AZT, 3'-azido-2',3'-dideoxy-5-iodouridine, 3'-azido-2',3'-dideoxy-5-bromouridine, and 2,5'-anhydro-3'-azido-3'-deoxythymidine (13) were found to be most active, with IC50 values of 0.023, 0.21, 0.23, and 0.27 microM, respectively.     

5-Cyano-2'-deoxyuridine 5'-phosphate: a potent competitive inhibitor of thymidylate synthetase.

The 5'-phosphate (1) of the antiviral nucleoside 5-cyano-2'-deoxyuridine was synthesized and evaluated for inhibition of thymidylate synthetase purified from methotrexate-resistant Lactobacillus casei. Compound 1 was a potent competitive inhibitor with a K1 of 0.55 microns. Irreversible enzyme inhibition by this compound could not be detected.     

Synthesis, structure, and antitumor and antiviral activities of a series of 5-halouridine cyclic 3',5'-monophosphates

A series of potential prodrug 5-halouridine 3',5'-cyclic monophosphates (5-X-cUMPs, X = F, Cl, Br, I, 1-4) has been prepared and tested for antitumor activity against murine leukemia L1210/0 and human lymphoblast Raji/0 cells and their deoxythymidine kinase deficient (TK-) counterparts, as well as for antiviral activity in primary rabbit kidney cells infected with herpes simplex virus type 1 or 2, vaccinia virus, or vesicular stomatitis virus. The 5-halopyrimidine bases, nucleosides (5-X-U), and 5'-monophosphates (5-X-UMP) were tested for comparison. 5-F-cUMP (1) showed reasonably potent inhibition of tumor cell proliferation (ID50 = 0.33-1.6 micrograms/mL), while the remaining diesters displayed ID50's ranging from 210 to greater than 1000 micrograms/mL. 5-F-cUMP was 70- to 300-fold less active than 5-F-dU in the same systems. With TK- L1210 cells, 5-F-cUMP was as potent as with the normal (L1210/0) line but was about fourfold less active with TK- Raji cells compared to Raji/0 cells. The 5-X-cUMPs showed little potency as antivirals. A single-crystal X-ray analysis of the ammonium salt of 5-I-cUMP confirmed its structure and showed the conformation of the phosphate ring to be the expected chair. The ribose pucker is near 3(4)T, and the torsion angle about the beta-glycosidic N(1)-C(1') bond is in the syn range (-84.8 degrees).     

2'-Fluorinated arabinonucleosides of 5-(2-haloalkyl)uracil: synthesis and antiviral activity

The synthesis of 5-(2-fluoroethyl)-2'-deoxyuridine (FEDU, 4b), its 2'-fluoro analogue 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-(2-fluoroethyl)-1H,3H- pyrimidine-2,4-dione (FEFAU, 4k), and the 2'-fluoro analogue of the potent antiherpes virus compound 5-(2-chloroethyl)-2'-deoxyuridine (CEDU), 5-(2-chloroethyl)-1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-1H,3H-pyr imidine - 2,4-dione (CEFAU, 4i), is described. The antiviral activities of these compounds were determined in cell culture against herpes simplex virus (HSV) types 1 and 2 and varicella zoster virus (VZV). All compounds were shown to possess significant and selective antiviral activity. FEDU proved less potent than CEDU against VZV replication; however, it was more active against HSV-2. CEFAU showed marked activity against HSV-1, HSV-2, and VZV. The compound containing fluorine at both positions, FEFAU, exhibited the strongest antiviral potency against HSV-1, HSV-2, and VZV. It inhibited HSV-1 at a concentration of 0.03-0.2 microgram/mL, HSV-2 at 0.1-0.3 microgram/mL, and VZV at 0.03 microgram/mL. Neither FEDU nor CEFAU or FEFAU exerted a significant inhibitory effect on cell proliferation at a concentration of 100 micrograms/mL. Thus, the cytotoxicity of these compounds is as low as that of CEDU and compares favorably to that of previously described 2'-fluoroarabinosyl nucleoside analogues.     

A novel synthesis and biological activity of several 5-halo-5'-amino analogues of deoxyribopyrimidine nucleosides

A novel synthetic procedure has been developed for the large-scale synthesis of 5-chloro-, 5-bromo-, and 5-iodo-5'-amino-2',5'-dideoxyuridine (4c-e) as well as of two new analogues, 5-iodo-5'-amino-2',5'-dideoxycytidine and 5-fluoro-5'-amino-2',5'-dideoxyuridine (4a and 4b), in good yield. The starting materials, 5-halo-2'-deoxyuridine and 5-halo-2'-deoxycytidine, are readily available and the method is straightforward. This report describes the synthesis and the biologial activities of these compounds.     

Synthesis, antiretrovirus effects, and phosphorylation kinetics of 3'-isocyano-3'-deoxythymidine and 3'-isocyano-2',3'-dideoxyuridine

The silylated AzddThd 5 and AzddUrd 6 prepared from 2,3'-anhydronucleoside derivatives 3 and 4 were transformed to formamides 7 and 8 by using the sequence RN3----RN = P(C6H5)----RNHCHO. Formamides 7 and 8 were dehydrated to the protected 3'-isocyano derivatives 9 and 10; deblocking gave 11 and 12. Neither 3'-isocyano-3'-deoxythymidine (11) nor 3'-isocyano-2',3'-dideoxyuridine (12) showed anti-HIV activity at noncytotoxic concentrations. ddThd derivative 11 was considerably more toxic to MT-4 cells than ddUrd derivative 12; it also had a much greater affinity (Ki) for MT-4 cell dThd kinase than ddUrd derivative 12. Both compounds appear to be linear mixed-type inhibitors of MT-4 cell dThd kinase.     

3'-Fluoro-2',3'-dideoxy-5-chlorouridine: most selective anti-HIV-1 agent among a series of new 2'- and 3'-fluorinated 2',3'-dideoxynucleoside analogues

A series of 2'- and 3'-fluorinated 2',3'-dideoxynucleosides and 3'-azido-2',3'-dideoxynucleosides were synthesized and evaluated for their inhibitory activity against human immunodeficiency virus-1 (HIV-1) replication in MT-4 cells. Neither conversion of 3'-fluoro- or 3'-azido-2',3'-dideoxyadenosine to the corresponding inosine derivatives nor 8-bromination of 2',3'-dideoxyadenosine resulted in increased anti-HIV-1 activity. Nor did introduction of a 2'-fluorine in the erythro or threo configuration lead to improved anti-HIV-1 activity of the parent 2',3'-dideoxynucleosides. 1-(2-Fluoro-2,3-dideoxy-beta-D-threo-pentofuranosyl)cytosine and 1-(2-fluoro-2,3-dideoxy-beta-D-erythropentofuranosyl)thymine were only marginally active. However, 3'-fluoro-2',3'-dideoxyuridine (FddUrd) proved to be potent and a relatively nontoxic inhibitor of HIV-1. 5-Halogenated derivatives of FddUrd were prepared in attempts to further increase its anti-HIV potency and selectivity. Of these 5-halogenated derivatives, 3'-fluoro-2',3'-dideoxy-5-chlorouridine emerged as the most selective inhibitor of HIV-1 replication. Its selectivity index was comparable to that of azidothymidine when evaluated under the same conditions.     

Synthesis and antitumor and antiviral properties of 5-alkyl-2'-deoxyuridines, 3',5'-cyclic monophosphates, and neutral cyclic triesters

A series of 5-alkyl-2'-deoxyuridine 3',5'-cyclic monophosphates (5-R-cdUMP's, R = Et, i-Pr, n-Pr, n-Bu, n-Pent, n-Hex, n-Oct) was prepared and tested in culture systems as antitumor and antiviral agents in comparison to the 5-alkyl-2'-deoxyuridines (5-R-dUrd's) themselves. Only the 5-Et- and 5-n-Bu-cdUMP showed appreciable cytostatic activities against murine L1210 and human lymphoblast Raji cells (ID50 range: 28-82 micrograms/mL). 5-Et-dUrd itself was much more active (ID50 = 1.6 and 2.9 micrograms/mL). The 5-i-Pr-, and 5-n-Bu-dUrd's were inactive, but activity increased again for groups with chain lengths of five carbons or greater. 5-Et-cdUMP and 5-Et-dUrd had greatly reduced activities against deoxythymidine kinase deficient (TK-) L1210 and Raji cells. 5-Et-cdUMP evidently is not an efficient prodrug source of the corresponding 5'-monophosphate where the TK- cells are concerned. Of the 5-R-cdUMP's, 5-Et-cdUMP displayed reasonably good antiviral potency against herpes simplex types 1 and 2 (MIC50, mostly 7-70 micrograms/mL) and vaccinia virus (MIC, 70 micrograms/mL). The activity was nonetheless 10- to 100-fold less than that for 5-Et-dUrd. The other 5-R-dUrd's generally showed decreasing antiviral activity with increasing 5-R chain length. Methyl and/or benzyl neutral triesters of certain 5-R-cdUMP's were inactive as antivirals and largely inactive against tumor cells in culture. In contrast to the 5'-monophosphates, the 5-R-cdUMP's failed to inhibit thymidylate synthetase from L1210 cells.     

Structure-activity relationships of pyrimidine nucleosides as antiviral agents for human immunodeficiency virus type 1 in peripheral blood mononuclear cells

The structure-activity relationships of several pyrimidine nucleosides related to 3'-azido-3'-deoxythymidine (AZT) were determined in human immunodeficiency virus type 1 (HIV-1) infected human peripheral blood mononuclear cells. These studies indicated that nucleosides with a 3'-azido group on the sugar ring exhibited the most potent antiviral activity. Substitution at C-5 with H, CH3, and C2H5 produced derivatives with the highest potency, whereas alkyl functions greater than C2, including bromovinyl substitution reduced the antiviral potency significantly. Changing the 3'-azido function to an amino or iodo group reduced the antiviral activity. Replacement of the uracil ring by cytosine or 5-methylcytosine produced analogues with high potency and low toxicity. Modification of the 5'-hydroxy group markedly reduced the antiviral activity. Similarly, various C-nucleoside analogues related to AZT and 2',3'-dideoxycytidine were inactive and nontoxic. From these systematic studies 3'-azido-2',3'-dideoxyuridine (5a), 3'-azido-5-ethyl-2',3'-dideoxyuridine (5c), and 3'-azido-2',3'-dideoxycytidine (7a) and its 5-methyl analogue (7b) were identified as potent and selective anti-HIV-1 agent in primary human lymphocytes.     

Synthesis and pharmacological properties of decahydro-5H-pyrido [1',2'; 5,1]imidazo[3,4-a]-beta-carbolines

Cyclic aminals (1-4) including a form of decahydro-5H-pyrido[1', 2'; 5, 1] imidazo [3, 4-a]-beta-carboline were obtained by treating erythro 1-(2'-piperidyl)-1,2,3,4-tetrahydro-beta-carboline with aldehydes. The central action of compounds 1-4 has been investigated using behavioral tests in mice and rats. The most active aminal was a phenyl derivative 4, which showed an anticonvulsive activity in the maximal electroshock seizure test. The overall activity of compound 4 was less potent than that of phenytoin.     

5'-O-phosphonomethyl-2',3'-dideoxynucleosides: synthesis and anti-HIV activity.

5'-O-Phosphonomethylation of different pyrimidine 2',3'-dideoxynucleosides was accomplished by reaction of the latter with diethyl [(p-toylsulfonyl)oxy]methanephosphonate (1) in the presence of sodium hydride. The base-phosphonomethylated (15-19) and sugar-phosphonomethylated (8-12) derivatives could be readily distinguished by 1H and 13C NMR and MS analysis. Protection of the uracil or thymine residue with a N3-benzoyl group failed to prevent base modification. However, O4-methyl-protected 2',3'-dideoxyuridine readily afforded the 5'-O-phosphonomethylated derivative 12, which was converted to both the 2',3'-didoxyuridine analogue 27 and the 2',3'-dideoxycytidine counterpart 29. The 5'-O-phosphonomethyl derivatives of 3'-deoxythymidine (23), 2',3'-dideoxyuridine, (27), 2',3'-dideoxycytidine (29), 3'-O-methylthymidine (26), and 3'-amino-3'-deoxythymidine (28) did not show an appreciable anti-HIV activity in MT-4 cells. In contrast, the 5'-O-phosphonomethyl derivatives of 3'-deoxy-3'-fluorothymidine (24) and 3'-azido-3'-deoxythymidine (25) inhibited HIV-1 cytopathogenicity by 50% at a concentration of approximately 1 microM.     

Synthesis and complement inhibitory activity of B/C/D-ring analogues of the fungal metabolite 6,7-diformyl-3',4',4a',5',6',7',8',8a'-octahydro-4,6',7'-trihydroxy- 2',5',5',8a'-tetramethylspiro[1'(2'H)-naphthalene-2(3H)-benzofuran

This paper reports the synthesis and the bioassay of 4-methoxy- and 4-hydroxyspiro[benzofuran-2(3H)-cyclohexane] partial analogues (5) of the complement inhibitory sesquiterpene fungal metabolite 6,7-diformyl-3',4',4a',5',6',7',8',8a'-octahydro-4,6',7'-trihydroxy-2',5',5',8a'-tetramethylspiro[1'(2'H)-naphthalene-2(3H)-benzofuran] (1a, K-76) and its silver oxide oxidized product (1b, K-76COOH). The described target compounds represent spirobenzofuran B/C/D-ring analogues lacking the A-ring component of the prototype structure. The target compounds were evaluated by the inhibition of total hemolytic complement activity in human serum. It was observed that the structurally simplified analogue 4-methoxyspiro[benzofuran-2(3H)-cyclohexane]-6-carboxylic acid (5a) exhibited an IC(50) = 0.53 mM similar to the IC(50) = 0.57 mM that was observed for the natural product derivative 1b. Exhibiting an IC(50) = 0.16 mM, the three-ringed partial structure 6-carboxy-7-formyl-4-methoxyspiro[benzofuran-2(3H)-cyclohexane] (5k)was found to be the most potent target compound. Like the natural product, 5k appears to inhibit primarily at the C5 activation step and inhibits both the classical and alternative human complement pathways. Several other analogues inhibited complement activation in vitro at concentrations similar to those required for inhibition by the natural product 1b.     

Cellular metabolism of 3'-azido-2',3'-dideoxyuridine with formation of 5'-O-diphosphohexose derivatives by previously unrecognized metabolic pathways for 2'-deoxyuridine analogs

3'-Azido-2',3'-dideoxyuridine (AzdU, CS-87) is a potent inhibitor of human immunodeficiency virus replication in human peripheral blood mononuclear cells (PBMC) with limited toxicity for human bone marrow cells (BMC). In the present study, metabolism of AzdU was investigated in human PBMC and BMC after exposure of cells to 2 or 10 microM [3H]AzdU. 3'-Azido-2',3'-dideoxyuridine-5'-monophosphate (AzdU-MP) was the predominant metabolite, representing approximately 55 to 65% of intracellular radioactivity in both PBMC and BMC at all times. The AzdU-5'-diphosphate and -5'-triphosphate intracellular levels were 10- to 100-fold lower than the AzdU-MP levels and, of note, AzdU-5'-triphosphate was not detected in human BMC. Using anion exchange chromatography, a new peak of radioactivity, distinct from any known anabolites, was detected. This chromatographic peak was found to be resistant to alkaline phosphatase but was hydrolyzed by 5'-phosphodiesterase, yielding AzdU-MP. Incubation of [3H]AzdU and D-[1-14C]glucose in PBMC and BMC produced a double-labeled peak with the same retention time as the anabolite, suggesting formation of a hexose derivative of AzdU. A novel high performance liquid chromatography method was developed that allowed for the separation of nucleosides, nucleotides, and carbohydrate derivatives thereof. Using this highly specific method, the putative AzdU-hexose actually was separated into two chromatographic peaks. These novel metabolites were identified as 3'-azido-2',3'-dideoxyuridine-5'-O-diphosphoglucose and 3'-azido-2',3'-dideoxyuridine-5'-O-diphospho-N-acetylglucosamine. Following 48 hr of incubation with [3H] AzdU, as much as 20 and 30% of these AzdU metabolites accumulated in PBMC and BMC, respectively. When AzdU was removed from the cell cultures, intracellular AzdU diphosphohexose concentrations decayed in a monophasic manner, with an elimination half-life of 14.3 hr. By 48 hr, levels of 0.3 pmol/10(6) cells were still detected, reflecting a gradual anabolism of these metabolites. Elimination of AzdU-MP and AzdU-5'-diphosphate was characterized by a two-phase process, with a short initial half-life of 0.83 and 0.24 hr and a long terminal half-life of 14.10 and 8.24 hr, respectively. Similar diphosphohexoses of deoxyuridine (dUrd) were also detected in human PBMC and BMC after exposure to [3H]dUrd, suggesting that dUrd derivatives are metabolized in a similar manner. In summary, the discovery of novel metabolic pathways for dUrd analogs demonstrates that AzdU has unique metabolic features that may contribute to the low toxicity of this anti-HIV agent in human BMC and also affect its mechanism of action.(ABSTRACT TRUNCATED AT 400 WORDS)