Synthesis, cytostatic, and antiviral activity of novel 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, 6-[2-(alkylsulfanyl)ethyl]-, and 6-[2-(dialkylamino)vinyl]purine nucleosides

An efficient and facile synthesis of a large series of diverse 6-[2-(dialkylamino)vinyl]-, 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, and 6-[2-(alkylsulfanyl)ethyl]purine nucleosides (35 examples of both ribo- and 2'-deoxyribonucleosides) was developed. The key transformations involved conjugate nucleophilic additions of amines, alcoholates, or thiolates to Tol-protected 6-alkylylpurine or 6-vinylpurine nucleosides. 6-[(2-Dialkylamino)vinyl]- and some 6-[(2-dialkylamino)ethyl]purine ribonucleosides exerted significant cytostatic effects and some anti-HCV activity with low selectivity.     

(E)-2-(2-Hydroxyethylidene)-6-methyl-5-heptenal (alpha-acariolal) and (E)-2-(2-hydroxyethyl)-6-methyl-2,5-heptadienal (beta-acariolal), two new types of isomeric monoterpenes from Caloglyphus polyphyllae (Acari: Acaridae)

The opisthonotal gland secretion of the acarid mite, Caloglyphus polyphyllae, contained two new monoterpenes, (E)-2-(2-hydroxyethylidene)-6-methyl-5-heptenal (1) and (E)-2-(2-hydroxyethyl)-6-methyl-2,5-heptadienal (2), to which we have given the trivial names alpha- and beta-acariolal in relation to alpha- and beta-acaridial (3 and 4), respectively. Elucidation of the structure of 1 was established mainly from 1H-NMR and GC/MS spectral data after partial purification, together with the fact that 1 was recovered in the more-polar fraction from a silica gel column than alpha- and beta-acaridial (3 and 4) present in the secretion. Compound 2 was obtained in the same fraction as a mixture with 1. Based on the facts that 2 had the same molecular weight by GC/MS and the same polarity as that of 1, compound 2 was assumed to be a structural analog of 1. The structures of compounds 1 and 2 were confirmed by their synthesis in nine and ten respective steps starting from alpha-bromo-gamma-butyrolactone.     

Enantioconvergent synthesis of (-)-(S)- and (+)-(R)-2-acetyl-3,6-dihydroxycyclohex-2-enone starting from rac-6-hydroxy-3-methoxycyclohex-2-enone

The synthesis of enantiomerically pure (-)-(S)- and (+)-(R)-2-acyl-3,6-dihydroxycyclohex-2-enone starting from diastereomerically pure N-tosyl-(S)-proline esters 3-methoxy-6-hydroxycyclohex-2-enone 1 is presented. An enantioconvergent synthesis of either (-)-(S)- and (+)-(R)-2-acyl-3,6-dihydroxycyclohex-2-enone starting with the racemic alpha-ketol 1 through a conversion of ( approximately 1:1) mixture of diastereomeric esters into one diastereomer by a repeated crystallization, followed by dimethylaminopyridine-catalyzed equilibration as key steps is described.     

Atropisomeric property of 1-(2,6-difluorobenzyl)-3-[(2R)-amino-2-phenethyl]-5-(2-fluoro-3-methoxyphenyl)-6-methyluracil

1-(2,6-Difluorobenzyl)-3-[(2R)-amino-2-phenethyl]-5-(2-fluoro-3-methoxyphenyl)-6-methyluracil (6), a potent and orally active antagonist of the human gonadotropin-releasing hormone receptor, exists as a pair of atropisomers in solution, which was detected by NMR spectroscopy, and separable by HPLC. In addition to a (R)-configured benzylamine, there is a second stereogenic element due to the presence of a chiral axis between the substituted 5-phenyl group and the uracil core. The rate constant of the interconversion (k = 5.07 x 10(-5) s(-1)) of these two atropisomers was determined by proton NMR analysis of a diastereoisomer-enriched sample in aqueous solution at 25 degrees C, and the corresponding Gibbs free energy DeltaG(#) of rotation barrier (97.4 kJ mol(-1)) was calculated using the Eyring equation. The diastereoisomer half-life at physiological temperature (37 degrees C) in aqueous media was estimated to be about 46 min.     

Microbial hydroxylation of (+/-)- and (-)-(2Z,4E)-5-(1',2'-epoxy-2',6',6'-trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid into (+/-)- and (-)-xanthoxin acid by Cunninghamella echinulata

Microbial hydroxylation of (+/-)-(2Z,4E)-5-(1',2'-epoxy-2',6',6'-trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid (3a) with Cercospora cruenta, a fungus producing (+)-abscisic acid, gave a four-stereoisomeric mixture consisting of (+)- and (-)-xanthoxin acid (4a), and (+)- and (-)-epi-xanthoxin acid (5a) by an HPLC analysis with a chiral column. Screening of the microorganisms capable of oxidizing (+/-)-3a showed that Cunninghamella echinulata stereoselectively oxidized (+/-)-3a to xanthoxin acid (4a) with the some degree of enantioselectivity as (-)-3a to (-)-4a.     

Syntheses of 6-(2-hydroxy-6-phenylhexyl)-5,6-dihydro-2H-pyran-2-one derivatives and their cytotoxicities

The cytotoxicities against cancer cells (HL-60, HeLa) and insect cells (Sf9) of four stereoisomers of 6-(2-hydroxy-6-phenylhexyl)− 5,6-dihydro-2H-pyran-2-one (1) were evaluated, and then their structure-activity relationships examined. The 2′-dehydroxy derivative 5 of (6 R,2′R)- and (6 R,2′S)-1 showed the highest activity against HeLa cells (IC₅₀ = 1.4 μM). To evaluate the effect of the 2′-hydroxy group of 1, 6R-and 6S-oxetane derivatives were also synthesized and their activities examined. Against HeLa and HL-60 cells, the activities of the less potent stereoisomers were enhanced 3–4-fold by the introduction of the oxetane moieties at the 2′-position. Against the insect cell line (Sf9), phenyl derivative 7 showed the highest activity with an IC₅₀ value of 8.0 μM.     

1-(2-Aminoethyl)-3-(arylsulfonyl)-1H-pyrrolopyridines are 5-HT6 receptor ligands

1-(2-Aminoethyl)-3-(arylsulfonyl)-1H-pyrrolopyridines were prepared. Binding assays indicated they are 5-HT₆ receptor ligands, among which 6f and 6g showed high affinity for 5-HT₆ receptors with K_i = 3.9 and 1.7 nM, respectively.     

Formation of DNA triple helix containing N(4)-(6-aminopyridin-2-yl)-2'-deoxycytidine.

A cytidinyl derivative, N(4)-(6-aminopyridin-2-yl)- 2'-deoxycytidine ((p)C), could interact with a CG base pair to support the triple-helix (triplex) formation of oligodeoxyribonucleotides. Characteristics of (p)C in the formation of both intramolecular triplex, i.e., a "paper clip type" triplex ((P)CT) and intermolecular triplex, i.e., a "linear type" triplex (LT) was monitored by optical methods and isothermal titration calorimetric measurements. Experimental results revealed that the LT with (p)C*CG internally was independent of the solution pH. Only single substitution of (p)C, situated internally but not terminally, facilitated the (P)CT formation by the UV thermal melting study at the neutral pH. However, the best stabilization of the PCT in acidic conditions occurred when (p)C at the end of the triplex rather than internally. In addition, an LT, but not a (P)CT, containing an alternating (p)CT(p)CT(p)C sequence, could be formed in the conditions of 20 mM MgCl(2) and/or 5 mM spermine. Thus, the presence of several nucleotides of (p)C in proximity along the Hoogsteen strand may lead to structural distortion such that the more flexible LT with multiple substitutions is formed in favor of the more rigid PCT.     

Synthesis of 1,5-Anhydro-2-(N 6-Cyclopentyladenin-9-Yl)-2-Deoxy-D-Altrohexitol

Abstract

The N ⁶-cyclopentyladenosine (CPA) analogue (4) was synthesized in 10 steps starting from glucose. The results of the radioligand binding assays are consistent with the thus far published findings that compounds containing a six-membered moiety at N ⁹ exhibit extremely weak affinity for adenosine receptors. Replacement of the ribofuranosyl moiety of CPA (2) by a 2-deoxy-D-altrohexitol moiety is sufficient to completely abolish its agonist activity.     

1-(2-((Z)-6-(2-(Trifluoromethyl)phenyl)hexa-3-en-1,5-diynyl)phenyl)piperidin-2-one as a new potent apoptosis agent

Compounds 4a–f, 5a–f and 6–9, showed significant growth inhibition activity against human tumor cell lines. Of these compounds, 1-(2-((Z)-6-(2-(trifluoromethyl)phenyl)hexa-3-en-1,5-diynyl)phenyl)piperidin-2-one (8) displayed the most potent growth inhibition activity. Compound 8 also arrested cancer cells in G2/M phase and induced apoptosis via activation of caspase-3 and -9. According to western-blotting analysis, compound 8 can up-regulate Bax, down-regulate Bcl-2 and XIAP, as well as promote cytochrome c release.     

1-N-methyl-(6E)-(2-methylpropylidene)-(3Z)-3-(phenylmethylene)-2,5-piperazinedione,a metabolite from Streptomyces albus

The structure and stereochemistry of a new piperazinedione, isolated from the cells of Streptomyces albus, are assigned on the basis of spectroscopic data, including comparison with related 2,5-piperazinediones.     

1-(2-Aminoethyl)-3-(arylsulfonyl)-1H-indoles as novel 5-HT6 receptor ligands

Novel 1-(2-aminoethyl)-3-(arylsulfonyl)-1H-indoles were prepared. Binding assays indicated they are 5-HT(6) receptor ligands, among which N,N-dimethyl-N-(2-[3-(1-naphthylsulfonyl)-1H-indol-1-yl]ethyl)amine 8t and N-methyl-N-(2-[3-(1-naphthylsulfonyl)-1H-indol-1-yl]ethyl)amine 8u showed high affinity for 5-HT(6) receptors with K(i)=3.7 and 5.7 nM, respectively.     

Radiolabeled guanine derivatives for the in vivo mapping of O(6)-alkylguanine-DNA alkyltransferase: 6-(4-[(18)F]Fluoro-benzyloxy)-9H-purin-2-ylamine and 6-(3-[(131)I]Iodo-benzyloxy)-9H-purin-2-ylamine

Two radiolabeled analogues of 6-benzyloxy-9H-purin-2-ylamine (O(6)-benzylguanine; BG) potentially useful in the in vivo mapping of O(6)-alkylguanine-DNA alkyltransferase (AGT) were synthesized. Fluorine-18 labeling of the known 6-(4-fluoro-benzyloxy)-9H-purin-2-ylamine (FBG; 6) was accomplished by the condensation of 4-[(18)F]fluorobenzyl alcohol with 2-aminopurin-6-yltrimethylammonium chloride (4) or 2-amino-6-chloropurine in average decay-corrected radiochemical yields of 40 and 25%, respectively. Unlabeled 6-(3-iodo-benzyloxy)-9H-purin-2-ylamine (IBG; 7) was prepared from 4 and 3-iodobenzyl alcohol. Radioiodination of 9, prepared from 7 in two steps, and subsequent deprotection gave [(131)I]7 in about 70% overall radiochemical yield. The IC(50) values for the inactivation of AGT from CHO cells transfected with pCMV-AGT were 15 nM for IBG and 50 nM for FBG. The binding of [(18)F]6 and [(131)I]7 to purified AGT was specific and saturable with both exhibiting similar IC(50) values (5-6 microM).     

2-(2-Chloro-6-fluorophenyl)acetamides as potent thrombin inhibitors

2-(2-Chloro-6-fluorophenyl)acetamides having 2,2-difluoro-2-aryl/heteroaryl-ethylamine P3 and oxyguanidine P1 substituents are potent thrombin inhibitors (K(i)=0.9-33.9 nM). 2-(5-Chloro-pyridin-2-yl)-2,2-difluoroethylamine was the best P3 substituent, yielding the most potent inhibitor (K(i)=0.7 nM). Replacing the P3 heteroaryl group with a phenyl ring or replacing the difluoro substitution with dimethyl or cyclopropyl groups in the linker reduced the affinity for thrombin significantly. The aminopyridine P1s also provided an increase in potency.     

Miscoding properties of 6alpha- and 6beta-diastereoisomers of the N(2)-(estradiol-6-yl)-2'-deoxyguanosine DNA adduct by Y-family human DNA polymerases

Treatment with estrogen increases the risk of breast, ovary, and endometrial cancers in women. DNA damage induced by estrogen is thought to be involved in estrogen carcinogenesis. In fact, Y-family human DNA polymerases (pol) eta and kappa, which are highly expressed in the reproductive organs, miscode model estrogen-derived DNA adducts during DNA synthesis. Since the estrogen-DNA adducts are a mixture of 6alpha- and 6beta-diastereoisomers of dG-N(2)-6-estrogen or dA-N(6)-6-estrogen, the stereochemistry of each isomeric adduct on translesion synthesis catalyzed by DNA pols has not been investigated. We have recently established a phosphoramidite chemical procedure to insert 6alpha- or 6beta-isomeric N(2)-(estradiol-6-yl)-2'-deoxyguanosine (dG-N(2)-6-E(2)) into oligodeoxynucleotides. Using such site-specific modified oligomer as a template, the specificity and frequency of miscoding by dG-N(2)-6alpha-E(2) or dG-N(2)-6beta-E(2) were explored using pol eta and a truncated form of pol kappa (pol kappaDeltaC). Translesion synthesis catalyzed by pol eta bypassed both the 6alpha- and 6beta-isomers of dG-N(2)-6-E(2), with a weak blockage at the adduct site, while translesion synthesis catalyzed by pol kappaDeltaC readily bypassed both isomeric adducts. Quantitative analysis of base substitutions and deletions occurring at the adduct site showed that pol kappaDeltaC was more efficient than pol eta by incorporating dCMP opposite both 6alpha- and 6beta-isomeric dG-N(2)-6-E(2) adducts. The miscoding events occurred more frequently with pol eta, but not with pol kappaDeltaC. Pol eta promoted incorporation of dAMP and dTMP at both the 6alpha- and 6beta-isomeric adducts, generating G --> T transversions and G --> A transitions. One- and two-base deletions were also formed. The 6alpha-isomeric adduct promoted slightly lower frequency of dCMP incorporation and higher frequency of dTMP incorporation and one-base deletions, compared with the 6beta-isomeric adduct. These observations were supported by steady-state kinetic studies. Taken together, the miscoding property of the 6alpha-isomeric dG-N(2)-6-E(2) is likely to be similar to that of the 6beta-isomeric adduct.     

Synthesis and structure-activity relationships of (R)-1-alkyl-3-[2-(2-amino)phenethyl]-5-(2-fluorophenyl)-6-methyluracils as human GnRH receptor antagonists

The synthesis of a series of (R)-1-alkyl-3-[2-(2-amino)phenethyl]-5-(2-fluorophenyl)-6-methyluracils is discussed. SAR around N-1 of the uracil was explored, which led to the discovery that an electron-deficient 2,6-disubstituted benzyl group is required for optimal receptor binding. The best compound from the series had binding affinity of 0.7 nM (K(i) for the human GnRH receptor, which was 8-fold better than the 2,6-difluorobenzyl analog.     

Synthesis of [6″-H]-, (6″-H)- and (2-H)-maltotriose

To prepare labeled precursors for biosynthetic studies, methods for the specific introduction of tritium and deuterium into the reducing and the terminal glucose unit of maltotriose were developed. Thus [6″-³H]- and (6″-²H)-maltotriose (17) and (18) were prepared via selective methoxytritylation, deprotection and subsequent modified Pfitzner-Moffatt oxidation, followed by reduction with sodium borotritiide or sodium borodeuteride, respectively. A simple two step procedure utilizing the Lobry de Bruyn/van Ekenstein transformation gave (2-²H)maltotriose (20).     

Synthesis of 6-substituted uridines. synthesis of (R or S)-6-(3-amino-2-carboxypropyl)uridine

Addition of 5-bromo-2′,3′-O-isopropylidene-5′-O-trityluridine (2) in pyridine to an excess of 2-lithio-1,3-dithiane (3) in oxolane at 78° gave (6R)-5,6-dihydro-(1,3-dithian-2-yl)-2′,3′-O-isopropylidene -5′-O-trityluridine (4), (5S,6S)-5-bromo-5,6-dihydro-(1,3-dithian-2-yl)-2′,3′-O-isopropylidene-5′-O-trityluridine (5), and its (5R) isomer 6 in yields of 37, 35, and 10%, respectively. The structure of 4 was proved by Raney nickel desulphurization to (6S)-5,6-dihydro-2′,3′-O-isopropylidene-6-methyl-5′-O-trityluridine (7) and by acid hydrolysis to give D-ribose and (6R)-5,6-dihydro-6-(1,3-dithian-2-yl)uracil (9). Treatment of 4 with methyl iodide in aqueous acetone gave a 30&%; yield of (R,S)-5,6-dihydro-6-formyl-2′,3′-O-isopropylidene-5′-O-trityl-uridine (10), characterized as its semicarbazone 11. Both 5 and 6 gave 4 upon brief treatment with Raney nickel. Both 5 and 6 also gave 6-formyl-2′,3′-O-isopropylidene-5′- O-trityluridine (12) in ～41%; yield when treated with methyl iodide in aqueous acetone containin- 10%; dimethyl sulfoxide. A by-product, identified as the N-methyl derivative (13) of 12 was also formed in yields which varied with the amount of dimethyl sulfoxide used. Reduction of 12 with sodium borohydride, followed by deprotection, afforded 6-(hydroxymethyl)uridine (17), characterized by hydrolysis to the known 6-(hydroxymethyl)uracil (18). Knoevenagel condensation of a mixture of the aldehydes 12 and 13 with ethyl cyanoacetate yielded 38%; of E- (or Z-)6-[(2-cyano-2-ethoxycarbonyl)ethylidene]-2′,3′-O-isopropylidene-5′-O-trityluridine (19) and 10%; of its N-methyl derivative 20. Hydrogenation of 19 over platinum oxide in acetic anhydride followed by deprotection gave R (or S)-6-(3-amino-2-carboxypropyl)uridine (23).