Nucleotide. X. Synthese und Eigenschaften von Dinucleosidmonophosphaten mit 2′-Desoxyadenosin und 1-(2′-Desoxy-β-D-ribofuranosyl)-lumazinen als Bausteine

Nucleotides. X. Synthesis and properties of dinucleoside monophosphates with 2′-deoxyadenosine and 1-(2′-deoxy-β-D -ribofuranosyl)-lumazines as building blocks The synthesis of various dinucleoside monophosphates 16--20 consisting of 2′-deoxyadenosine and 1-(2′-deoxy-β-D -ribofuranosyl)-lumazines via the triester approach is described. The fully protected phosphotriesters 6--10 as well as the partially deblocked intermediates 11--15 have also been isolated and characterized by physical means. Intramolecular interactions in 16--20 have been investigated by the determination of the hypochromicities and CD. spectra revealing a more or less distinct stacking effect in dependence of the 6,7-substituents in the lumazine moiety as well as the polarity of the internucleotidic linkage. Enzymatic degradations of the dinucleoside monophosphates with snake venom and spleen phosphodiesterase are depending strongly on various structural features indicating a much lower substrate specificity especially in presence of 6,7-diphenyl-lumazine as an aglycone with the latter enzyme.     

Nucleosides and nucleotides. Part 25.. Synthesis of a protected 1-(2′-deoxy-β-D-ribofuranosyl)-1 H-benzimidazole 3′-phosphate

1-(2′-Deoxy-5′-O-dimethoxytrityl-′-D -ribofuranosyl)-1 H-benzimidazole 3′-[(p-chlorophenyl)(2-cyanoethyl) phosphate] ( 6 ) has been synthesized from 1-(β-D -ribofuranosyl)-1H-benzimidazole ( 3b ) using regiospecific 2′-deoxygenation. The latter compound was obtained by glycosylation of benzimidazole with the D -ribose derivative 2 leading exclusively of the β-D -anomer.     

Nucleoside und Nucleotide. Teil 16. Verhalten von 1-(2′-Desoxy-β-D-ribofuranosyl)-2(1 H)-pyrimidinon-5′-triphosphat, 1-(2′-Desoxy-β-D-ribofuranosyl)-2(1 H)pyridinon-5′-triphosphat und 4-Amino-1-(2′-Desoxy-β-D-ribofuranosyl)-2(1 H)-pyridinon-5′-triphosphat gegenüber DNA-Polymerase

Nucleosides and Nucleotides. Part 16. The Behaviour of 1-(2′-Deoxy-β-D -ribofuranosyl)-2(1H)-pyrimidinone-5′-triphosphate, 1-(2′-Deoxy-β-D -ribofuranosyl-2(1H))-pyridinone-5′-triphosphate and 4-Amino-1-(2′-desoxy-β-D -ribofuranosyl)-2(1H)-pyridinone-5′-triphosphate towards DNA Polymerase The behaviour of nucleotide base analogs in the DNA synthesis in vitro was studied. The investigated nucleoside-5′-triphosphates 1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyrimidinone-5′-triphosphate (pppM_d), 1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridinone-5′-triphosphate (pppII_d) and 4-amino-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridinone-5′-triphosphate (pppZ_d) can be considered to be analogs of 2′-deoxy-cytidine-5′-triphosphate. However, their ability to undergo base pairing to the complementary guanine is decreased. When pppM_d, pppII_d or pppZ_d are substituted for pppC_d in the enzymatic synthesis of DNA by DNA polymerase no incorporation of these analogs is observed. They exhibit only a weak inhibition of the DNA synthesis. The mode of the inhibition is uncompetitive which shows that these nucleotide analogs cannot serve as substrates for the DNA polymerase.     

Nucleoside und Nucleotide. Teil 10. Synthese von Thymidylyl-(3′-5′) -thymidylyl-(3′-5′)-1-(2′-desoxy-β-D-ribofuranosyl)-2(1 H)-pyridon

Nucleosides and Nucleotides. Part 10. Synthesis of Thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D - ribofuranosyl)-2(1 H)-pyridone The synthesis of 5′-O-monomethoxytritylthymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1H)-pyridone ((MeOTr)T_dpT_dp∏_d, 5 ) and of thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridone (T_dpT_dp∏_d, 11 ) by condensing (MeOTr) T_dpT_d ( 3 ) and p∏_d(Ac) ( 4 ) in the presence of DCC in abs. pyridine is described. Condensation of (MeOTr) T_dpT_dp ( 6 ) with Π_d(Ac) ( 7 ) did not yield the desired product 5 because compound 6 formed the 3′-pyrophosphate. The removal of the acetyl- and p-methoxytrityl protecting group was effected by treatment with conc. ammonia solution at room temperature, and acetic acid/pyridine 7 : 3 at 100°, respectively. Enzymatic degradation of the trinucleoside diphosphate 11 with phosphodiesterase I and II yielded T_d, pT_d and p∏_d, T_dp and Π_d, respectively, in correct ratios.     

Nucleotides. Part XXVI.. A new synthesis of 9-(′-D-ribofuranosyl)uric acid and its 5′-monophosphate

Syntheses for 9-(β-D -ribofuranosyl)uric acid ( 16 ) and its 5′-monophosphate 14 have been achieved starting from guanosine and applying the 2-(p-nitrophenyl)ethyl group for protection of the aglycon moiety as well as the phosphate function. A more efficient and direct approach to 14 uses O⁶, O⁸-dibenzyl protection and phosphorylation by the Yoshikawa procedure. The various protected intermediates have been characterized by spectroscopic means and elemental analysis.     

Nucleotides. Part XXXIVSynthesis of Modified Oligomeric 2′–5′A Analogues: Potential Antiviral Agents

A series of new 2′–5′-oligonucleotide trimers carrying a 9-(2′,3′-anhydro-β-D -ribofuranosyl)-( 59 ), 9-(3′-deoxy-β-D -glycero-pent-3-enofuranosyl)-( 63 ), 9-(3′-azido-3′-deoxy-β-D -xylofuranosyl)-( 62 ), and 9-(3′-halo-3′-deoxy-β-D -xylofuranosyl)adenine ( 60 and 61 ) moiety at the 2′-terminal end have been synthesized via the phosphotriester method. The properly protected, modified monomeric building blocks ( 6 , 9 , 16 , 19 , 27 , 33 , 36 , 37 , and 43 ) were obtained, in general, by a sequence of reactions, introducing the protecting groups into the right positions. Their condensations with the intermediary dimeric 2′-terminal phosphodiesters 48 and 49 led to the fully protected 2′–5′-trimers 50–58 which were deblocked to form the free 2′–5′-trimers 59 – 63 . Easy elimination of HBr on deprotection did not allow to form the trimeric (3′-bromo-3′-deoxy-β-D -xylofuranosyl)adenine analogue but only 63 carrying an unsaturated sugar moiety instead. The newly synthesized compounds have been characterized by UV and NMR spectra as well as by elemental analysis.     

Nucleosides. Part L.. Structure of lumazine N1-(2′-deoxy-D-ribonucleosides) ( = 1-(2′-deoxy-D-ribofuranosyl)pteridine-2,4(1H,3H)-diones): A revision of the anomeric configuration

The anomeric configuration of the glycosidic bond in lumazine N¹-(2′-deoxy-D -ribonucleosides) 1–6 was investigated by NOE difference spectroscopy. The former configurational assignment of the α - and β -D -anomers 1 and 2, 3 and 4 , and 5 and 6 , respectively, has to be reversed to be in agreement with the physical data. Additional proof is presented by X-ray analysis of 3 and 6 . Chemical interconversions of 1-(2′-deoxy-β-D -ribofuranosyl)-6,7-diphenyllumazine ( 6 ) into 2,3′ -anhydrolumazine 2′-deoxyribonucleosides 16 and 17 are also in agreement with the revised anomeric configuration.     

Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1- (3′-O-Phosphoryl-2′-deoxy-β -D-ribofuranosyl)-2(1H)-pyridone-(3′-5′)-1-(2′-deoxy-β-D-ribofuranosyl)-2 (1H)-pyridone

The dinucleoside phosphate Π_dpΠ_d ( 4 ) was synthesized from the monomers 1-(5′-O-monomethoxytrityl - 2′ - deoxy - β - D - ribofuranosyl) - 2 (1 H) - pyridone ((MeOTr) Π_d, 2 ) and 1-(5′-O-phosphoryl-3′-O-acetyl-2′-deoxy-β-D -ribofuranosyl)-(1H)-pyridone (pΠ_d(Ac), 3 ). Its 6.4% hyperchromicity and an analysis of the ¹H-NMR. spectra indicate that the conformation and the base-base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.     

Saturated heterocycles. 242. Synthesis of 2-substituted-6-(6′,7′-dimethoxy-3′,4′-dihydro-1′-isoquinolyl)-5,6,7,8-tetrahydro- quinazolin-4(3H)-one Derivatives

In the reactions of the recently synthesized β-ketoesters 1-[(3′-methoxycarbonyl- and 1-[(3′-ethoxycarbonyl-4′-oxo)-1′-cyclohexyl]-3,4-dihydroisoquinoline 4, 5 with amidines or cyclic guanidines, a number of 2-substituted-6-(6′,7′-dimethoxy-3′,4′-dihydro-1′-isoquinolyl)-5,6,7,8-tetrahydroquinazolin-4(3H)-one derivatives 6–8 were prepared. The new compounds possess various pharmacological actions.     

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.     

Nucleoside und Nucleotide. Teil 15. Synthese von Desoxyribonucleosid-monophosphaten und -triphosphaten mit 2(1H)-Pyrimidinon, 2(1H)-Pyridinon und 4-Amino-2(1H)-pyridinon als Basen

Nucleosides and Nucleotide. Part 15. Synthesis of Deoxyribonucleoside Monophosphates and Triphosphates with 2(1H)-Pyrimidinone, 2(1H)-Pyridinone and 4-Amino-2(1H)-pyridinone as the Bases The phosphorylation of the modified nucleosides 1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyrimidinone (M_d, 4 ), 4-amino-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridinone (Z_d, 6 ) and the synthesis of 1–2′-deoxy-β-D -ribofuranosyl-2(1 H)-pyrimidinone-5′-O-triphosphate (pppM_d, 1 ), 1-(2′-deoxy-β-D ribofuranosyl)-2(1 H)-pyridinone-5′-O-triphosphate (pppII_d, 2 ), and 4-amino-1-(2′-deoxy-βD -ribofuranosyl)-2(1 H)-pyridinone-5′-O-triphosphate (pppZ_d, 3 ) are described. The nucleoside-5′-monophosphates pM_d (5) and pZ_d (7) were obtained by selective phosphorylation of M_d (4) and Z_d (6) , respectively, using phosphorylchloride in triethyl phosphate or in acetonitril. The reaction of pM_d (5) pII _d (8) or pZ_d (7) with morpholine in the presence of DCC led to the phosphoric amides 9, 10 and 11 , respectively, which were converted with tributylammonium pyrophosphate in dried dimethylsulfoxide to the nucleoside-5′triphosphates 1, 2 and 3 , respectively.     

Nucleotides,Part LXV,Synthesis of 2′‐Deoxyribonucleoside 5′‐Phosphoramidites: New Building Blocks for the Inverse (5′‐3′)‐Oligonucleotide Approach

The syntheses of the 3′‐O‐(4,4′‐dimethoxytrityl)‐protected 5′‐phosphoramidites 25 – 28 and 5′‐(hydrogen succinates) 29 – 32 , which can be used as monomeric building blocks for the inverse (5′‐3′)‐oligodeoxyribonucleotide synthesis are described (Scheme). These activated nucleosides and nucleotides were obtained by two slightly different four‐step syntheses starting with the base‐protected nucleosides 13 – 20 . For the protection of the aglycon residues, the well‐established 2‐(4‐nitrophenyl)ethyl (npe) and [2‐(4‐nitrophenyl)ethoxy]carbonyl (npeoc) groups were used. The assembly of the oligonucleotides required a slightly increased coupling time of 3 min in application of the common protocol (see Table 1). The use of pyridinium hydrochloride as an activator (instead of 1H‐tetrazole) resulted in an extremely shorter activation time of 30 seconds. We established the efficiency of this inverse strategy by the synthesis of the oligonucleotide 3′‐conjugates 33 and 34 which carry lipophilic caps derived from cholesterol and vitamin E, respectively, as well as by the formation of (3′‐3′)‐ and (5′‐5′)‐internucleotide linkages (see Table 2).     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. VIII. Synthese von (3S,3′S)-7,8,7′,8′-Tetradehydroastaxanthin und (3S,3′S)-7,8-Didehydroastaxanthin (Asterinsäure)

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. VIII. Synthesis of (3S,3′S)-7,8,7′,8′-Tetradehydroastaxanthin and (3S,3′S)-7,8-Didehydroastaxanthin (Asterinic Acid) The synthesis of all-trans-(3S,3′S)-3,3′-dihydroxy-7,8, 7′,8′-tetradehydro-β, β-carotene-4,4′-dione ( 1 ), of all-trans-(3S,3′S)-3,3′-dihydroxy-7, 8-didehydro-β,β-carotene-4,4′-dione ( 2 ) (asterinic acid = mixture of 1 and 2 ), and of their 9,9′-di-cis- and 9-cis-isomers is reported starting from (4′S)(2E)-5-(4′-hydroxy-2′, 6′,6′-trimethyl-3′-oxo-l′-cyclohexenyl)-3-methyl-2-penten-4-ynal ( 8 ). The absolute configuration (3S,3′S) for both components 1 and 2 of asterinic acid ex Asterias rubens is confirmed on the basis of spectroscopic and direct comparison.     

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.     

Nucleotides. Part XXXVI. Syntheses and biological characterization of phosphorothioate analogues of (3′–5′)adenylate trimer

The four protected diastereoisomcrs 7a / 7b and 8a / 8b P-thioadenylyl-(3′–5′)-P-thioadenylyI-(3′–5′)-adenosine were synthesized, separated, and deblocked to the free oligonucleotides (Scheme). Biochemical characterization of these (3′–5′)phosphorothioate analogues of adenyiate trimer indicate that these compounds, and the corresponding 5′-monophosphates, neither bind to nor activate RNase L, and are considered to be valuable control compounds in screening experiments.     

Nucleotide,XVII. Synthese von homogenen Adenosyl-3′,5′-Oligomeren nach dem Phosphotriester-Verfahren

Nucleotides, XVII. Synthesis of Homogeneous Adenosyl-3′,5′-oligomers by the Phosphotriester Method The chemical synthesis of the fully protected trimer 12 , the tetramers 11 and 23 as well as the pentamer 14 was achieved in preparative scales starting from the fully blocked adenosine-3′-phosphotriesters 1, 2 , and N⁶-benzoyl-2′,3′-bis-O-(tert-butyldimethylsilyl)adenosine (6) . All intermediates and end products have been isolated, purified and characterized by elemental analyses, UV, and CD spectra. Deprotection of the various blocking groups proceeds without difficulties to afford the free trimeric, tetrameric, and pentameric oligoadenylates 15, 16 , and 24 in high yields.     

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 ).