Nucleotides Part LI. Synthesis and biological activities of (2′-5′)adenylate trimer conjugates with 2′-terminal 3′-O(ω-hydroxyalkyl) and 3′-O-(ω-carboxyalkyl) spacers

An efficient strategy for the synthesis of (2′-5′)adenylate trimer conjugates with 2′-terminal 3′-O-(ω-hydroxyalkyl) and 3′-O-(ω-carboxyalkyl) spacers is reported. Npeoc-protected adenosine building blocks 37--40 for phosphoramidite chemistry carrying a 3′-O-[11-(levulinoyloxy)undecyl], 3′-O-{2-[2-(levulinoyloxy)ethoxy]ethyl}, 3′-O-[5-(2-cyanoethoxycarbonyl)pentyl], and 3′-O-{5-[(9H-fluoren-9-ylmethoxy)carbonyl]pentyl} moiety, respectively, were prepared (npeoc = 2-(4-nitrophenyl)ethoxycarbonyl). Condensation with the cordycepin (3′-deoxyadenosine) dimer 1 led to the corresponding trimers 42, 43, 47 , and 48. Whereas the levulinoyl (lev) and 9H-fluoren-9-ylmethyl (fm) blocking groups could be cleaved off selectively from the trimers 42, 43 , and 48 yielding the intermediates 44, 45 , and 49 for the synthesis of the 3′-O-(ω-hydroxyalkyl)trimers 53, 54 and the cholesterol conjugates 59--61 , the 2-cyanoethyl (ce) protecting group of 47 , however, could not be removed in a similar manner from the carboxy function. Trimer 47 served as precursor for the preparation of the trimer 55 with a terminal 3′-O-(5-carboxypentyl)adenosine moiety. The metabolically stable 3′-O-alkyl-(2′--5′)A derivatives were tested regarding inhibition of HIV-1 syncytia formation and HIV-1 RT activity. Only the conjugate 59 showed significant effects, whereas the trimers 53--55 and the conjugates 60 and 61 were less potent inhibitors, even at 100-fold larger concentrations.     

Un nouvel exemple de nucléoside à sucre ramifié insaturé: la désoxy-3′-méthylidène-3′-adénosine

A Novel Example of Unsaturated Branched-chain Sugar Nucleoside: 3′-Deoxy-3′-methylidene-adenosine Starting from 5-O-benzoyl-3-C-methylidene-3-deoxy-1,2-O-isopropylidene-α-D -erythro-pentofuranose ( 11 ) the title compound 8 has been prepared. Its α-anomer ( 9 ) and the acyclic sugar nucleoside 10 have been obtained as by-products. Adenosine deaminase slowly deaminated 8, 9 being not affected. Compound 8 exhibited no antiviral activity, whereas one of its saturated analogues ( 13 ) inhibited the multiplication of the herpes-1 (HF) virus.     

Synthèse et désamination enzymatique des C-hydroxyméthyl-3′- et C-méthyl-3′-β-D-xylofurannosyl-9-adénines

Synthesis and enzymatic deamination of 3′-C-hydroxymethyl- and 3′-C-methyl-β-D -xylofuranosyl-9-adenines The title compounds have been prepared by classical synthetic steps after having optimized the nature of the blocking groups. Both nucleosides were found to be substrates of adenosine aminohydrolase which proved that C(3′)-branched-chain sugar nucleosides can be deaminated when the branched-chain is exo (trans relative to the base) if a suitably disposed hydroxy group is available on the endo side of the furanose ring.     

Halochrome Molekeln 8. Mitteilung. Synthese und acidobasisches Verhalten von 3′-substituierten 6,11-Dihydrospiro[[1]benzopyrano[4,3-b]indol-6,9′−9′H-xanthenen]

Halochromic Molecules. Synthesis and Acidobasic Properties of 3′-substituted 6,11-dihydrospiro[[1]benzopyrano[4,3-b]indol-6,9′?9′9′H-xanthenes] We have synthesized a series of 3′-substituted 6,11-ihydrospiro[6H-chromeno[4,3-b]indol–6,9′?9′H-xanthenes] and one of their respective aza analogues. ¹H-MR data as well as the fragmentation in the mass spectra of starting and final products supported the postulated structures. With acid, the spiro compounds form ring-opened intensely coloured xanthylium salts. UV/VIS spectra of these salts are listed and discussed. The ?_pH* curves in buffered MeOH/H₂O solutions and the pK* values are determined. The title compounds could possibly be used in ‘pressure sensitive papers’.     

Un nouvel analogue synthétique de l'adénosine: La désoxy-3′-C-dibromométhylidène-3′-adénosine

A novel synthetic analog of adenosine: the 3′-deoxy-3′-C-dibromomenthylidene-adenosine The title compound ( 7 ) has been prepared by a sequence of classical synthetic steps from 3-deoxy-3-C-dibromomethylidene-1,2: 5,6-di-O-isopropylidene-α-D -ribo-hexofuranose ( 1 ). The β-configuration of the nucleoside was established by formation of a cyclonucleoside. 7 is very slowly deaminated by adenosine deaminase. In contrast with its dichloro analog, it does not inhibit the growth of Escherichia coli.     

A method for the synthesis of racemic and optically active 2-substituted 9-(2′,3′-dihydroxypropyl)-8-azahypoxanthines and 8-azaadenines

Several 9-(2′,3′-O-isopropylidene)- and 9-(2′,3′-dihydroxypropyl)-8-azahypoxanthines and 8-azaadenines were synthesized by a “one pot” method starting from the acetonide of racemic or (S)-1-azido-2,3-dihydroxypropane, obtained from D-mannitol. 9-(2′,3′-Dihydroxypropyl)-8-azapurines were tested as adenosine deaminase inhibitors.     

Synthèses dans la série des bis-indéno-fluorènes,VI [1] Dihydro-12, 15–6H-bis-indéno[1. 2-b; 2′.1′-h]fluorène et dihydro-14, 15–8H-bis-indéno[2. 1-a; 2′. 1′-h]fluoréne

Starting from cyclohexene and 2, 2′, 5, 5′-tetramethylbiphenyl the linear bisindenofluorene 12, 15-dihydro-6H-diindeno [1.2-b; 2′.1′-h] fluorene (XX) has been synthesized in 5 steps (overall yield 27%). As an intermediate product the 6, 12, 15-trioxo-derivative XIX (greyish green crystals, blue alcaline vat) was obtained. By a side way, the 6-oxo-derivative of XX and the already known monoangular bis-indenofluorene 14, 15-dihydro-8H-diindeno [2.1-a; 2′.1′ -h] fluorene (XXVII) were also obtained. XX can also be prepared in several steps starting from 3-methyl-fluorene or fluorene.     

Synthèses dans la série des bis-indéno-fluorènes V [1]. Dihydro-13, 15–11 H-bis-indéno[2, 1-b; 1′, 2′-h]fluorène et dihydro-13, 15–5H-bis-indéno[1, 2-a; 1′, 2′-h]fluorène

Starting from cyclohexene and 2, 2′, 4, 4′-tetramethylbiphenyl the linear bis-indenofluorene 13, 15-dihydro-11 H-diindeno [2, 1-b; 1′, 2′-h] fluorene (X) has been synthetised in 5 steps (overall yield 30%). As an intermediate product the 11, 13, 15-trioxo-derivative IX was obtained. By a side way the 13-oxo-derivative of X and the already known monoangular bis-indenofluorene 13, 15-dihydro-5 H-diindeno [1, 2-a; 1′, 2′-h] fluorene (XIX) were also obtained.     

2′, 3′-Dideoxy-3′-fluorotubercidin and Related Dideoxyribonucleosides:. Synthesis via a 2′-deoxy-3′-oxoribofuranoside intermediate and conformation studies

An efficient synthesis of the unknown 2′-deoxy-D-threo-tubercidin ( 1b ) and 2′, 3′-dideoxy-3′-fluorotubercidin ( 2 ) as well as of the related nucleosides 9a, b and 10b is described. Reaction of 4-chloro-7-(2-deoxy-β-D-erythro-pentofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine ( 5 ) with (tert-butyl)diphenylsilyl chloride yielded 6 which gave the 3′-keto nucleoside 7 upon oxidation at C(3′). Stereoselective NaBH₄ reduction (→ 8 ) followed by deprotection with Bu₄NF(→ 9a )and nucleophilic displacement at C(6) afforded 1b as well as 7-deaza-2′-deoxy-D-threo-inosine ( 9b ). Mesylation of 4-chloro-7-{2-deoxy-5-O-[(tert-butyl)diphenylsilyl]-β-D-threo-pentofuranosyl}-7H-pyrrolo[2,3-d]-pyrimidine ( 8 ), treatment with Bu₄NF (→ 12a ) and 4-halogene displacement gave 2′, 3′-didehydro-2′, 3′-dideoxy-tubercidin ( 3 ) as well as 2′, 3′-didehydro-2′, 3′-dideoxy-7-deazainosne ( 12c ). On the other hand, 2′, 3′-dideoxy-3′-fluorotubercidin ( 2 ) resulted from 8 by treatment with diethylamino sulfurtrifluoride (→ 10a ), subsequent 5′-de-protection with Bu₄NF (→ 10b ), and Cl/NH₂ displacement. ¹H-NOE difference spectroscopy in combination with force-field calculations on the sugar-modified tubercidin derivatives 1b , 2 , and 3 revealed a transition of the sugar puckering from the ^3′T_2′ conformation for 1b via a planar furanose ring for 3 to the usual ^2′T_3′ conformation for 2.     

Nucleotides. Part XLV. Synthesis of new (2′–5′)adenylate trimers,containing 5′-amino-5′-deoxyadenosine residues at the 5′-end of the oligoadenylate chain,and of its analogues,carrying a 9-[(2-hydroxyethoxy)methyl]adenine residue at the 2′-terminus

The 5′-amino-5′-deoxy-2′,3′-O-isopropylideneadenosine ( 4 ) was obtained in pure form from 2′,3′-O-isopropylideneadenosine ( 1 ), without isolation of intermediates 2 and 3 . The 2-(4-nitrophenyl)ethoxycarbonyl group was used for protection of the NH₂ functions of 4 (→7) . The selective introduction of the palmitoyl (= hexadecanoyl) group into the 5′-N-position of 4 was achieved by its treatment with palmitoyl chloride in MeCN in the presence of Et₃N (→ 5 ). The 3′-O-silyl derivatives 11 and 14 were isolated by column chromatography after treatment of the 2′,3′-O-deprotected compounds 8 and 9 , respectively, with (tert-butyl)dimethylsilyl chloride and 1H-imidazole in pyridine. The corresponding phosphoramidites 16 and 17 were synthesized from nucleosides 11 and 14 , respectively, and (cyanoethoxy)bis(diisopropylamino)phosphane in CH₂Cl₂. The trimeric (2′–5′)-linked adenylates 25 and 26 having the 5′-amino-5′-deoxyadenosine and 5′-deoxy-5′-(palmitoylamino)adenosine residue, respectively, at the 5′-end were prepared by the phosphoramidite method. Similarly, the corresponding 5′-amino derivatives 27 and 28 carrying the 9-[(2-hydroxyethoxy)methyl]adenine residue at the 2′-terminus, were obtained. The newly synthesized compounds were characterized by physical means. The synthesized trimers 25–28 were 3-, 15-, 25-, and 34-fold, respectively, more stable towards phosphodiesterase from Crotalus durissus than the trimer (2′–5′)ApApA.     

Syntheses of 6,8-disubstituted-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphates

A series of 6,8-disubstituted-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphates were prepared employing preformed 9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate precursors. Three synthetic approaches were utilized to accomplish the syntheses. The first approach involved a study of the order of nucleophilic substitution, 6 vs 8, of the intermediate 6,8-dichloro-9-β-D-ribofuranosyipurine 3′,5′-cyclic phosphates ( 2 ) with various nucleophilic agents to yield 8-amino-6-chloro-, 8-chloro-6-(diethylamino)-, 6-chloro-8-(diethylamino)-, 6,8-bis-(diethylamino)- and 8-(benzylthio)-6-chloro-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate (4, 9, 10, 11, 13) respectively and 6-chloro-9-β-D-ribofuranosylpurin-8-one 3′,5′-cyclic phosphate ( 5 ) and 8-amino-9-β-D-ribofuranosylpurine-6-thione 3′,5′-cyclic phosphate ( 6 ). The order of substitution was compared to similar substitutions on 6,8-dichloropurines and 6,8-dichloropurine nucleosides. The second scheme utilized nucleophilic substitution of 6-chloro-8-substituted-9-β-D-ribofuranosylpurine 3′,5′-cyclic, phosphates obtained from the corresponding 8-subslituted inosine 3′,5′-cyclic phosphates by phosphoryl chloride, 6,8-bis-(benzylthio)-, 6-(diethylamino)-8-(benzylthio),8-(p-chlorophenylthio(-6-(diethylamino)- and 6,8-bis-(methyl-thio)-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphates ( 14, 12, 20 , and 21 ) respectively, were prepared in this manner. The final scheme involved N¹-alkylation of an 8-substituted adenosine 3′,5′-cyclic phosphate followed by a Dimroth rearrangement to give 6-(benzylamino)-8-(methylthio)- and 6-(benzylamino)-8-bromo-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate ( 24 and 25 ).     

Synthèses dans la série des bis-indéno-fluorènes,VIII. Méthyl-6-dihydro-9,15-7H-bis-indéno[2.1-b;2′.1′-g]fluorène

Starting from 5-benzoyl-2,4-dibromobenzoic acid and 3-methyl-fluorene, the 6-methyl-9,15-dihydro-7H-diindeno[2.1-b; 2′,1′-g]fluorene, a derivative of a mono-angular diindenofluorene has been synthesized in 5 steps (overall yield 1,5%).     

Synthesis of 5-Methyluridine and Its 5′-Mercapto-, 2-Amino-, and 4′,5′-Unsaturated Analogues

The stereospecific cis-hydroxylation of 1-(2,3-dideoxy-β-D -glyceropent-2-enofuranosyl)thymine (1) into 1-β-D -ribofuranosylthymine (2) by osmium tetroxide is described. Treatment of 2′,3′-O, O-isopropylidene-5-methyl-2,5′-anhydrouridine (8) with hydrogen sulfide or methanolic ammonia afforded 5′-deoxy-2′,3′-O, O-isopropylidene-5′-mercapto-5-methyluridine (9) and 2′,3′-O, O-isopropylidene-5-methyl-isocytidine (10) , respectively. The action of ethanolic potassium hydroxide on 5′-deoxy-5′-iodo-2′,3′-O, O-isopropylidene-5-methyluridine (7) gave rise to the corresponding 1-(5-deoxy-β-D -erythropent-4-enofuranosyl)5-methyluracil (13) and 2-O-ethyl-5-methyluridine (14) . The hydrogenation of 2 and its 2′,3′-O, O-isopropylidene derivative 4 over 5% Rh/Al₂O₃ as catalyst generated diastereoisomers of the corresponding 5-methyl-5,6-dihydrouridine ( 17 and 18 ).     

8-Aza-7-deaza-2′,3′-dideoxyguanosine: Deoxygenation of its 2′deoxy-β-D-ribofuranoside

The synthesis of 6-amino-1-(2′,3′-dideoxy-β-D -glycero-pentofuranosyl)-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one ( =8-aza-7-deaza-2′,3′-dideoxyguanosine; 1 ) from its 2′-deoxyribofuranoside 5a by a five-step deoxygenation route is described. The precursor of 5a, 3a , was prepared by solid-liquid phase-transfer glyscosylation which gave higher yields (57%) than the liquid-liquid method. Ammonoloysis of 3b furnished the diamino nucleoside 3c . Compound 1 was less acid sensitive at the N-glycosydic bond than 2′,3′-dideoxyguanosine ( 2 ).     

8-Aza-2′-deoxyguanosine and Related 1,2,3-Triazolo[4,5-d]pyrimidine 2′-Deoxyribofuranosides

The synthesis of 8-azaguanine N⁹-, N⁸-, and N⁷-(2′-deoxyribonucleosides) 1–3 , related to 2′-deoxyguanosine ( 4 ), is described. Glycosylation of the anion of 5-amino-7-methoxy-3H-1,2,3-triazolo[4,5-d]pyrimidine ( 5 ) with 2-deoxy-3,5-di-O-(4-toluoyl)-α-D -erythro-pentofuranosyl chloride ( 6 ) afforded the regioisomeric glycosylation products 7a/7b, 8a/8b , and 9 (Scheme 1) which were detoluoylated to give 10a, 10b, 11a, 11b , and 12a . The anomeric configuration as well as the position of glycosylation were determined by combination of UV, ¹³C-NMR, and ¹H-NMR NOE-difference spectroscopy. The 2-amino-8-aza-2′-deoxyadenosine ( 13 ), obtained from 7a , was deaminated by adenosine deaminase to yield 8-aza-2′-deoxyguanosine ( 1 ), whereas the N⁷- and N⁸-regioisomers were no substrates of the enzyme. The N-glycosylic bond of compound 1 (0.1 N HCl) is ca. 10 times more stable than that of 2′-deoxyguanosine ( 4 ).     

Nucleotide. XV. Synthese und Eigenschaften von 2′-O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleosid-3′-phosphotriestern,Ausgangssubstanzen für Oligonucleotid-Synthesen

Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide Syntheses The syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6–14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1–5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6 , 8 , 10 , 12 and 14 and by p-nitrophenylethanol to 7 , 9 , 11 and 13 . These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15–23 with free HO? C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24–32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses.     

Etude Conformationnelle par Résonance Magnétique Nucléaire Protonique des Dérivés de la O-Isopropylidène-2′,3′ Adénosine

Conformational analysis using ¹H n.m.r. data (δ, ³J and NOE) has been carried out on several derivatives of 2′,3′,-O-isopropylideneadenosine bearing various substituents at positions C-5′, C-8 and N-6. Conformational modifications are assigned to specific interactions between the sugar and purine moieties and also to solvent effects.     

Vier neue Metabolite von Giberella zeae: 5-Formyl-zearalenon, 7′-Dehydrozearalenon, 8′-Hydroxy- und 8′-epi-Hydroxy-zearalenon

From cultures of Gibberella zeae ergosterol, zearalenone ( 1 ) and hitherto unknown minor metabolites, i.e.. 5-formyl-zearalenone ( 6 ), 7′-dehydrozearalenone ( 8 ), 8′-hydroxyzearalenone ( 9 ) and 8′-epi-hydroxyzearalenone ( 11 ) were isolated. The production of zearalenone and its congeners proved to be very strongly dependent on the conditions of culture. 5-Formyl-zearalenone ( 6 ) as well as 3-formylzearalenone ( 4 ) were synthesized from zearalenone ( 1 ) and characterized by the di-O-methyl derivatives 7 and 5 respectively. The structure of 7′- dehydrozearalenone ( 8 ) was deduced from spectral data. The di-O-methyl derivatives 10 and 12 respectively of the two corresponding epimeric 8′-hydroxy derivatives 9 and 11 yielded the same β-diketone 13 . The keto-enol equilibrium of 13 was studied.     

Synthesis of 2′-Deoxyisoinosine and Related 2′-Deoxyribonucleosides

Various 2-substituted purine and pyrrolo[2,3-d]pyrimidine 2′-deoxyribonucleosides with methylthio ( 13a ), chloro ( 13b ), methoxy ( 9b ), and oxo ( 2, 3 ) substituents at C(2) are prepared. They are obtained either via stereoselective nucleobase-anion glycosylation or by base transformation. A three-step synthesis of the unknown 2′-deoxyisoinosine ( 2 ) from 2′-deoxyguanosine ( 15 ) is described. Compound 2 as well as its 7-deazapurine derivative 3 exhibit strong fluorescence.