Structure and synthesis of 6-(substituted-imidazol-1-yl)purines: versatile substrates for regiospecific alkylation and glycosylation at N9

X-ray crystal structures of several 6-(azolyl)purine base and nucleoside derivatives show essentially coplanar conformations of the purine and appended 6-(azolyl) rings. However, the planes of the purine and imidazole rings are twisted approximately 57 degrees in a 2-chloro-6-(4,5-diphenylimidazol-1-yl)purine nucleoside, and a twist angle of approximately 61 degrees was measured between the planes of the purine and pyrrole rings in the structure of a 6-(2,5-dimethylpyrrol-1-yl)purine nucleoside derivative. Shielding "above" N7 of the purine ring by a proximal C-H on the 6-azolyl moiety is apparent with the coplanar compounds, but this effect is diminished in those without coplanarity. Syntheses of 6-(azolyl)purines from both base and nucleoside starting materials are described. Treatment of 2,6-dichloropurine with imidazole gave 2-chloro-6-(imidazol-1-yl)purine. Modified Appel reactions at C6 of trityl-protected hypoxanthine and guanine derivatives followed by detritylation gave 6-(imidazol-1-yl)- and 2-amino-6-(imidazol-1-yl)purines. Imidazole was introduced at C6 of 2',3',5'-tri-O-acetylinosine by a modified Appel reaction, and solvolysis of the glycosyl linkage gave 6-(imidazol-1-yl)purine. Guanosine triacetate was transformed into the protected 2,6-dichloropurine nucleoside, which was subjected to S(N)Ar displacement with imidazoles at C6 followed by glycosyl solvolysis to provide 2-chloro-6-(substituted-imidazol-1-yl)purines. Potential applications of these purine derivatives are outlined.     

6-(2-Alkylimidazol-1-yl)purines undergo regiospecific glycosylation at N9

[reaction: see text] Regioselective control of glycosylation of purines at N9 (versus N7) has been a continuing challenge. We now report Lewis acid catalyzed regiospecific glycosylations of 6-(2-alkylimidazol-1-yl)purines at N9. The 6-(2-alkyl)imidazole moiety also functions as a versatile leaving group that can be replaced by nucleophiles (S(N)Ar) and aryl groups (Suzuki cross-coupling).     

C(6)N(7)-cyclized purines

By reaction of 6-[N-(2-hydroxyethyl)-N-methyl]aminopurine ( 2a ) and of the corresponding 3-hydroxypropyl derivative 2b with thionyl chloride a bridge to N(1) is formed yielding 5 and 6 , respectively, whereas from 6-[N-(4-hydroxybutyl)-N-methyl]aminopurine ( 2c ) the 4-chlorobutyl compound 4 is obtained, which cyclizes in alkaline medium to the C(6)-N(7) bridged compound 7 . A related cyclization to 11a–11f is observed when 6-chloropurines are reacted with 3-alkyl-1,3-oxazolidines or 3-methyl-1,3-thiazolidine.     

Synthesis of 6-substituted 9-(dihydroxyalkyl) purines

5-Amino-6-chloro-4-dihydroxyalkylaminopyrimidines, which are cyclized to 6-chloro-9-(dihydroxyalkyl)purines, were obtained by the condensation of 5-amino-4,6-dichloropyrimidine with 2-amino-1,3-dihydroxypropane or with 2-amino-1,4-dihydroxybutane. The corresponding 6-hydroxy and 6-amino derivatives were obtained by replacement of the chlorine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 262–264, February, 1971.     

Purinenucleoside analogs. 2. 9-(1-Alkoxyethyl-1)-6-substituted purines

Vinyl ethers react with 6-chloro- and 6-methylthiopurines in acid medium to give 9-(1-alkoxyethyl-1)-6-chloro- and 6-methylthiopurines. The 6-chloro compounds were used to prepare 9-(1-alkoxyethyl-1)-6-mercaptopurines. All the synthesized compounds proved to be inactive against lympholeucosis P 388, and Lewis carcinona grafted under kidney capsules in mice.For Communication 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–406, March, 1986.     

Recent progress in the synthesis of N7(N9)-alkyl(aryl)purines (microreview)

Chemistry of Heterocyclic Compounds - Recent progress from 2015 to 2022 in alkylation and arylation reactions of purine N-7 and N-9 positions is shown.     

Synthesis of (aryl/heteroaryl)-(6-(aryl/heteroaryl)pyridin-3-yl)methanones

Research on Chemical Intermediates - One-pot condensation of aryl/heteroaryl β-enaminones and ammonium acetate in the presence of CeCl3·7H2O–NaI led to the formation of novel...     

Traceless solid-phase synthesis of N1,N7-disubstituted purines

A highly regioselective and traceless solid-phase route to N1,N7-disubstituted purines has been developed. Key steps in the reaction strategy involves (i) coupling of 6-chloropurine to the REM resin (Michael addition), (ii) oxidation, (iii) N1-alkylation, (iv) quaternization, and (v) product release through Hofmann elimination. A library of 15 N1,N7-disubstituted purines was synthesized.     

The use of 15N-NMR spectroscopy for assigning the structures of isomeric N7- and N9-substituted purines

An ¹⁵N-NMR study has shown a considerable difference in electronic structures between the isomeric N⁷ and N⁹ substituted purines. A comparison of ¹⁵N chemical shifts amongst the seven pairs of N⁷ and N⁹ isomers has revealed that (1) the N³ resonances are shielded by 18–20 ppm in an N⁹ isomers; (2) the amino nitrogens at the C-2 or at C-6 positions are always shielded by 3–4 ppm in the N⁷ isomers; (3) the N⁷ chemical shifts in the N⁷ isomers are always more shielded by 6–7 ppm than the N⁹ resonances in the N⁹ isomers. It has a also been found by protonation studies that the N⁹ of the N⁷ isomer is much more basic than the N⁷ of the N⁹ isomer.     

Synthesis and structure of 6-substituted 9-(2-ethoxy-1,3-dioxan-5-yl)purines

The reaction of 4-chloro-5-amino-6-(1,3-dihydroxy-2-propyl)aminopyrimidine with excess ethyl orthoformate gave a cyclic acetal, viz., 6-chloro-9-(2-ethoxy-1,3-dioxan-5-yl)purine, amination of which yielded 6-amino-9-(2-ethoxy-1,3-dioxan-5-yl)purine. The presence of two configurational isomers with a diaxial orientation of the purine ring and the ethoxy group in the trans isomer and an equatorial orientation of the ethoxy group in the cis isomer was established for these compounds by ¹H and ¹³C NMR and IR spectroscopy. The three-dimensional structure of trans-6-chloro-9-(2-ethoxy-1,3-dioxan-5-yl)purine was determined by an x-ray difraction study, and the trans-diaxial orientation of the purine ring and the ethoxy group was confirmed; it is shown that the dioxane ring is in an anti conformation relative to the purine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 976–983, July, 1979.     

Facile and efficient synthesis of 6-(hydroxymethyl)purines

[reaction: see text] A facile and efficient methodology of the synthesis of 6-(hydroxymethyl)purine derivatives (bases and nucleosides) was developed based on Pd-catalyzed cross-coupling reactions of 6-halopurines with acyloxymethylzinc iodides followed by deprotection. Several title compounds are inhibitors of adenosine deaminase and exert cytostatic activity.     

First Total Synthesis of (-)-4-O-(6'-hydroxy-7'(9')-dehydro-6',7'-dihydrogeranyl)-coniferyl Alcohol

SomeLigulariaspecieshavelongbeenusedasfolkremediesduetotheirantibiotic,antiphlogisticandantitumoracti.ities'.Compound1',anovelconiferylalcoho1,wasisolatedfromLigulariaduciformis(Compsitae)alongwiththreenewstructuressuchas2,3,4(Figure1).Thegeometricalstructureof1,deterndnedbyspectroscopictechniques,correspondedto4-o-(6'-hydroxy-7'(9')-dehydro-6coniferylalcohol.ButitsabsoluteconfigurationatC-6'hasnotyetbeendetermined.Hereinwereportthetotalsynthesisof(6'S)-(-)-lfromgeraniol5throughninesteps(Sc…     

Palladium(II)-catalyzed one-pot syntheses of 9-(pyridin-2-yl)-9H-carbazoles through a tandem C-H activation/C-X (X=C or N) formation process

A new one-pot synthesis of 9-(pyridin-2-yl)-9H-carbazoles through the simultaneous C-H activation and palladium(II)-catalyzed cross-coupling of N-phenylpyridin-2-amines with potassium aryltrifluoroborates is presented. Silver acetate and 1,4-dioxane proved to be the best oxidant and solvent, respectively. The product yields fluctuated from modest to excellent and the reaction showed sufficient functional group tolerance. p-Benzoquinone served as an important ligand for the transmetalation and reductive elimination steps in the catalytic process. The kinetic isotope effects (k(H)/k(D)) for the first and second C-H activation/C-C or C-N formation steps were measured as 2.14 and 1.18, respectively. Finally, a rational catalytic mechanism is presented based on all experimental evidence.     

4a,6-Bis-(N-methlanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthen-1,4-dion: Ein thermolyseprodukt von 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dion

Summary 4a,6-Bis-(N-methylanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthene-dione (4) was obtained by thermolysis of 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dione (1) The structure was determined on basis of 1D- and 2D-NMR techniques.Herrn Prof. Dr. G. Zigeuner zum 70. Geburtstag gewidmet     

Synthesis and some properties of 6-(ω-aroylbutylthio)purines

A series of 6-(ω-aroylthio)purines, which have not been described in the literature, has been obtained by the reaction of 6-purinethione with ω-chlorovalerophenone and its substituted derivatives. Some properties of the compounds synthesized have been studied, viz. reaction at the carbonyl group, methylation, and hydrolysis. All-Russian Scientific Center for the Safety of Biologically Active Substances, Staraya Kupavna, Moscow region 142450. Zaporozhe State Medical University, Zaporozhe 330074, Ukraine. Center for Drug Chemistry, All-Russian Pharmaceutical Chemistry Research Institute, Moscow 119815. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1407–1411, October, 1999.     

Synthesis and characterization of N(1)-(4-toluenesulfonyl)-N(1)- (9-anthracenemethyl)triamines

A modular synthetic approach was developed to access triamines with varying tether lengths from commercially available aminoalkanols. Initial N-alkylation via reductive amination with anthracene-9-carbaldehyde provided the secondary amines in good yield. Subsequent ditosylation with excess TsCl yielded the respective bis-N,O-tosylates. The tosylates were reacted with excess putrescine to give the final triamines. X-ray crystallography revealed that the polyamine tail is preferentially oriented over the shielding cone of the anthracene ring.