合成路线1

The condensation of 2-amino-6-chloropurine (I) with ethyl 4-bromo-2-hydroxybutyrate (II) by means of K2CO3 in DMF gives ethyl 4-(2-amino-6-chloropurin-9-yl)-2-hydroxybutyrate (III), which 8-hydrolyzed with refluxing aqueous HCl yielding 4-(9-guanyl)-2-hydroxybutyric acid (IV). The esterification of (IV) with ethanol - HCl affords the corresponding ethyl ester (V), which is finally reduced with NaBH4 in refluxing isopropanol.

合成路线2

The condensation of 2-amino 6 chloropurine (I) with 2-benzyioxyethoxymethyl chloride (II), by means of K2CO3 in DMF gives 2-amino-6 chloro 9-(2 benzyloxyethoxymethyl)purine (III), which is then dechlorinated by reduction with H2 over Pd/C in ethanol containing triethylamine.

合成路线3

By the condensation of 2-amino-6-chloropurine (I) (which has been silylated with 1,1,1,3,3,3-hexamethyldisilazane) with (1,3-dibenzyloxy-2-propoxy)methyl chloride (II) by means of mercuric cyanide in benzene at reflux. BIOLF-7O is purified by chromatography over silica gel.

合成路线4

This compound has been obtained by two similar ways: 1) The reaction of 6-chloropurine-2-amine (I) with 6,6-dimethyl-5,7-dioxaspiro[2.5]octane-4,8-dione (II) by means of K2CO3 in DMF gives the expected condensation product (III), which is methanolized with HCl/methanol yielding 2-[2-(2-amino-6-methoxypurin-9-yl)ethyl]malonic acid dimethyl ester (IV). The reduction of (IV) with NaBH4 in tert-butanol/methanol affords the corresponding diol (V), which is finally converted into pecnciclovir by hydrolysis with 2N NaOH. 2) The reaction of purine (I) with 3-bromopropane-1,1,1-tricarboxylic acid triethyl ester (VI) by means ofK2CO3 in DMF gives the expected condensation product (VII), which is partially decarboxylated with sodium methoxide in methanol yielding 2-[2-(2-amino-6-chloropurin-9-yl)ethyl]malonic acid diethyl ester (VIII). The reduction of (VIII) with NaBH4 in tert-butanol/methanol followed by acetylation with acetic anhydride affords the corresponding diol diacetate (IX), which is finally converted into penciclovir by hydrlysis with 2N HCl.

合成路线5

A synthesis of famciclovir that corresponds to that previously published and studies on its oral bioavailability in rats and mice, identifying famciclovir as the preferred prodrug of BRL-39123 (penciclovir), have been published.

合成路线6

The reaction of purine (I) with 3-bromopropane-1,1,1-tricarboxylic acid triethyl ester (II) by means ofK2CO3 in DMF gives the expected condensation product (III), which is partially decarboxylated with sodium methoxide in methanol yielding 2-[2-(2-amino-6-chloropurin-9-yl)ethyl]malonic acid diethyl ester (IV). The reduction of (IV) with NaBH4 in tert-butanol/methanol followed by acetylation with acetic anhydride affords the corresponding diol diacetate (V), which is finally converted into famciclovir by reductive dechlorination with H2 over Pd/C in ethyl acetate/triethylamine.

合成路线7

A new synthetic route to famciclovir has been described: The alkylation of 2,2-dimethyl-1,3-dioxan-5-one (I) with vinylmagnesium bromide (II) in THF gives the 2,2-dimethyl-5-vinyl-1,3-dioxan-5-ol derivative (II), which is treated with methyl chloroformate in the same solvent to yield the mixed carbonate (IV). Condensation of (IV) with 6-chloropurine-2-amine (V) by means of 1,2-bis(diphenylphosphino)ethane (dppe) and tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] in DMF at 80 °C for 7.5 h affords a 5:95 mixture of the N-7 (VI) and N-9 (VII) regioisomers, respectively. Hydrogenation of regioisomer (VII) with H2 over Pd/C in THF eliminates the 6-chlorine atom and reduces the exocyclic double bond giving the 2-aminopurine derivative (VIII), which is treated with HCl in methanol to remove the acetonide group affording diol (IX). Finally, this compound is acylated with acetic anhydride and DMAP/TEA in dichloromethane.

合成路线8

The condensation of 6-chloropurine-2-amine (I) with epoxide (II) by means of Pd(PPh3)4 in DMSO gives the cyclopentenol derivative (III), which is treated with dimethyl dicarbonate and DMAP in dichloromethane to yield the carbonate (IV). The condensation of (IV) with ethyl 2-nitroacetate (V) by means of Pd in THF affords the adduct (VI), which is decarboxylated by means of NaCl in DMSO/water at 150 C to provide the nitromethylcyclopentene derivative (VII). The reaction of (VII) with tBuOK, O3 and NaBH4 in methanol gives the corresponding hydroxymethyl derivative (VIII), which is finally hydrolyzed with NaOH in refluxing water to afford the target guanine as a racemic compound. Alternatively, the nitromethyl-cyclopentene derivative (VII) can also be obtained by condensation of carbonate (IV) with 2-(trimethylsilyl)ethyl 2-nitroacetate (IX) by means of Pd in THF to give the adduct (X), which is decarboxylated by means of CsF in hot acetonitrile, affording (VII).

合成路线9

The condensation of 6-chloropurine-2-amine (III) with the chiral monoacetate (II) (obtained by enzymatic desymmetrization of diacetate (I)) by means of Pd(PPh3)4 in DMSO gives the cyclopentenol derivative (IV), which is treated with dimethyl dicarbonate and DMAP in dichloromethane to yield the carbonate (V). The condensation of (V) with ethyl 2-nitroacetate (VI) by means of Pd in THF affords the adduct (VII), which is decarboxylated by means of NaCl in DMSO/water at 150 C to provide the nitromethylcyclopentene derivative (VIII). The reaction of (VIII) with tBuOK, O3 and NaBH4 in methanol gives the corresponding hydroxymethyl derivative (IX), which is finally hydrolyzed with NaOH in refluxing water to afford the target guanine as a racemic compound. Alternatively, the nitromethyl-cyclopentene derivative (VIII) can also be obtained by condensation of carbonate (V) with 2-(trimethylsilyl)ethyl 2-nitroacetate (X) by means of Pd in THF to give the adduct (XI), which is decarboxylated by means of CsF in hot acetonitrile, affording (VIII).

合成路线10

The reaction of the chiral epoxy-alcohol (I) with MsCl, TEA and DMAP gives the mesylate (II), which is treated with TBAF in THF to yield the unsaturated epoxide (III).The condensation of (III) with diaminopurine (IV) by means of NaH in DMF affords the carbocyclic purine (V), which is dehydroxylated by reaction with phenyl chlorothioformate, followed by a thermal elimination reaction with Bu3SnH and AIBN to provide the carbocyclic purine (VI). The debenzylation of (VI) by means of BF3/Et2O and Ac2O gives the diacetyl derivative (VII), which is selectively O-deacetylated with NH3 in methanol, yielding 2-acetamido-6-aminopurine (VIII). The reaction of (VIII) with NaNO2 and acetic acid affords the N-acetylated guanine derivative (IX), which is finally treated with NH3 in methanol to provide the target compound.

合成路线11

The condensation of the cis-dibenzoyloxycyclopentene (I) with the lithium salt of 2-nitrovinyl(phenyl)sulfone (II) by means of a chiral palladium catalyst and PPh3 in THF gives the chiral isoxazoline-N oxide (III), which is deoxygenated by means of SnCl2 in acetonitrile, yielding the isoxazoline (IV). The solvolysis of (IV) with K2CO3 in methanol affords the methoxy compound (V), which is treated with Mo(CO)6 and boric acid in methanol to provide the chiral 2-hydroxy-3-cyclopentene-1-carboxylic acid methyl ester (VI). The reduction of (VI) with LiAlH4 in ether yields the hydroxymethyl derivative (VII), which is esterified with methyl chloroformate and BuLi in THF to afford the bis-carbonate (VIII). The condensation of (VIII) with 2-amino-6-chloropurine (IX) by means of a Pd catalyst in THF provides the carbocyclic purine (X), which is finally treated with NaOH in refluxing water to yield the target carbocyclic guanine.

合成路线12

The photooxidation of cyclopentadiene (I) gives cis-4-cyclopentene-1,3-diol (II), which is acylated with Ac2O to yield the diacetate (II). Enzymatic selective hydrolysis of (II) using porcine pancreas lipase (PPL) affords the chiral monoacetate (IV), which is protected with dihydropyran (DHP) and Ts-OH to provide the tetrahydropyranyl ether (V). The hydrolysis of the acetate group of (V) with KOH in methanol gives the alcohol (VI), which is silylated with TbdmsCl and imidazole to yield the silyl ether (VII). Elimination of the THP-protecting group of (VII) with Me2AlCl in dichloromethane affords the cyclopentenol (VIII), which is oxidized with PCC to the cyclopentenone (IX). The condensation of (IX) with chloroiodomethane and BuLi in THF gives the chiral chloromethyl derivative (X), which is treated with potassium methoxide in THF to obtain the chiral epoxide (XI). Stereocontrolled opening of the epoxide ring of (XI) by means of DIBAL in hexane provides the cyclopentenyl-methanol derivative (XII), which is desilylated with TBAF in THF to give the chiral diol (XIII). The esterification of the diol (XIII) with methyl chloroformate and pyridine yields the bis-carbonate (XIV), which is condensed with 2-amino-6-chloropurine (XV) by means of Pd(PPh3)4 in DMF to afford the carbocyclic purine derivative (XVI). Finally, this compound is hydrolyzed with NaOH in refluxing water to provide the target carbocyclic guanine.

合成路线13

The reaction of cyclopentadiene (I) with tosyl cyanide in acidic water gives the racemic bicyclic lactam (II), which is opened by means of TsCl and NaH to yield cis-3-(tosylamino)-4-cyclopentene-1-carboxylic acid (III). The reduction of (III) with NaBH4 affords the corresponding carbinol (IV), which is acylated with Ac2O and pyridine to provide the acetate (V). The reaction of (V) with Ts-Cl and NaH yields the ditosylamino derivative (VI), which is condensed with 2-amino-6-chloropurine (VII) by means of a Pd catalyst, affording the carbocyclic purine (VIII). Finally, this compound is hydrolyzed with hot aqueous NaOH to give the target carbocyclic guanine.

合成路线14

The epoxidation of 3-cyclopentene-1-carboxylic acid methyl ester (I) with MCPBA in cyclohexane gives the trans-epoxide (II) along with some cis-isomer that is separated by chromatography. The reduction of the ester group of (II) with LiAlH4 in ether yields the corresponding trans-carbinol (III), which is silylated with Tbdms-Cl and imidazole to afford the silyl ether (IV). The reaction of the epoxide (IV) with the chiral lithium pyrrolidide (V) in benzene provides the (1S,3S)(trans) 3-(tertbutyldimethylsilyloxy)-4-cyclopenten-1-ol (VI). The condensation of (VI) with 2-amino-6-chloropurine by means of diethyl azodicarboxylate (DEAD) and PPh3 in dioxane gives the carbocyclic purine derivative (VIII), which is desilylated by means of TBAF in THF to the chloropurine (IX). Finally, this compound is hydrolyzed with refluxing aqueous NaOH to yield the target carbocyclic guanine.

合成路线15

The addition of HCl to cyclopentadiene (I) gives 3-chlorocyclopentene (II), which is converted to racemic 2-cyclopentene-1-carboxylic acid (III). Optical resolution of (II) by crystallization of its (-)-1-phenylethylamine yields the desired enantiomer (IV), which is reduced with LiAlH4 in ethyl ether affording the chiral carbinol (V) (ee 98%). The reaction of (V) successively with BuLi, CO2 and I2 provides the iodinated cyclic carbonate (VI), which is treated with DBU in hot toluene to give the unsaturated cyclic carbonate (VII). The condensation of (VII) with 2-amino-6-chloropurine (VIII) by means of a Pd catalyst yields the carbocyclic purine (IX), which is finally hydrolyzed with aqueous NaOH to afford the target carbocyclic guanine. Alternatively, carbinol (V) can also be obtained by the vitamin B12/Zn/NH4Cl-catalyzed isomerization of 1,2-epoxycyclopentane (X) to the chiral cyclopentenol (XI), which by a [2,3]-sigmatropic Wittig rearrangement with KH, ICH2-SnBu4 and BuLi yields the target carbinol (V). However, the enantiomeric excess obtained is only ee 54%.

合成路线16

The condensation of 6-chloropurine-2-amine (III) with the chiral monoacetate (II) (obtained by enzymatic desymmetrization of diacetate (I)) by means of Pd(PPh3)4 in DMSO gives the cyclopentenol derivative (IV), which is treated with dimethyl dicarbonate and DMAP in dichloromethane to yield the carbonate (V). The condensation of (V) with ethyl 2-nitroacetate (VI) by means of Pd in THF affords the adduct (VII), which is decarboxylated by means of NaCl in DMSO/water at 150 C to provide the nitromethylcyclopentene derivative (VIII). The reaction of (VIII) with tBuOK, O3 and NaBH4 in methanol gives the corresponding hydroxymethyl derivative (IX), which is finally hydrolyzed with NaOH in refluxing water to afford the target guanine as a racemic compound. Alternatively, the nitromethyl-cyclopentene derivative (VIII) can also be obtained by condensation of carbonate (V) with 2-(trimethylsilyl)ethyl 2-nitroacetate (X) by means of Pd in THF to give the adduct (XI), which is decarboxylated by means of CsF in hot acetonitrile, affording (VIII).

合成路线17

The reaction of the commercially available (1S-cis)-2-cyclopentan-1,4-diol 4-acetate (I) with methyl pyrocarbonate and DMAP in THF gives the carbonate ester (II), which by reaction with nitromethane (III), triisopropyl phosphite and a Pd catalyst, yields (1R-cis)-1-acetoxy-4-(nitromethyl)-2-cyclopentene (IV). The hydrolysis of (IV) by means of Ts-OH in methanol affords the corresponding alcohol (V), which by treatment with O3, NaOMe and NaBH4 in methanol provides (1R-cis)-4-(hydroxymethyl)-2-cyclopenten-1-ol (VI). The selective monotritylation of the primary OH group of (VI) with trityl chloride (VII) in pyridine gives the trityl ether (VIII), which is condensed with 2-amino-6-chloropurine (IX) by means of Pd(PPh3)4 in THF to yield the adduct (X). The destritylation of (X) with HOAc/water affords the hydroxymethyl compound (XI), which is finally dechlorinated by hydrolysis with hot HCl or NaOH to provide the target (-)-carbovir. Alternatively, the dechlorination of (XI) can be performed by reaction of (XI) with liquid ammonia at 75-80 C in a Parr bomb to give the diaminopurine (XII), which is finally submitted to an enzymatic deamination with adenosine deaminase (from calf intestinal mucosa).

合成路线18

The cyclization of glyoxylic acid (I) with cyclopentadiene (II) gives the racemic hydroxylactone (III), which is acylated with Ac2O to yield acetoxy compound (rac)-(IV). The enzymatic optical resolution of (rac)-(IV) by means of Pseudomonas fluorescens affords the chiral hydroxylactone (-)-(V), which is reduced with LiAlH4 in refluxing THF to provide the lactol (VI). The oxidation of (VI) with NaIO4 in ethyl ether/water gives the chiral carbaldehyde (VII), which is reduced with NaBH4 in ethanol to afford the diol (VIII). The reaction of (VIII) with triphosgene by means of TEA in dichloromethane affords the cyclic carbonate (IX), which is condensed with chloropurine (X) by means of Pd(PPh3)4 in DMSO/THF to provide the adduct (XI). Finally, this compound is hydrolyzed with NaOH to afford the target (-)-carbovir.

合成路线19

1) The cyclization of ketene diethylketal (I) with diethyl fumarate (II) in hot tert-butanol gives trans-3,3-diethoxycyclobutane-1,2-dicarboxylic acid diethyl ester (III), which is saponified with KOH in hot methanol to the corresponding racemic diacid (IV). The condensation of (IV) with (R)-(-)-2-phenylglycinol (V) by means of dicyclohexylcarbodiimide (DCC) in dichloromethane followed by fractionated crystallization of the resulting diastereomeric mixture yields the diamide (VI). The hydrolytic reduction of (VI) by sequential treatments with trimethylsilyl chloride and imidazole, dinitrogen tetraoxide and finally with LiBH4 affords (S,S)-trans-3,3-diethoxycyclobutane-1,2-dimethanol (VII), which is benzoylated with benzoyl chloride in pyridine to the dibenzoate (VIII). The cleavage of the ketal group of (VIII) with H2SO4 in acetonitrile gives the cyclobutanone (IX), which is reduced with LS-Selectride in THF yielding [1S-(1alpha,2beta,3beta)]-3-hydroxycyclobutane-1,2-dimethanol 1,2-dibenzoate (X). The reaction of (X) with p-toluenesulfonyl chloride affords the corresponding tosylate (XI), which is condensed with 6-O-benzylguanidine (XII) by means of K2CO3 and 18-crown-6 in hot DMF giving [1R-(1alpha,2beta,3alpha)]-6-O-benzyl-9-[2,3-di(benzoyloxymethyl) cyclobutyl]guanine (XIII). Finally, this compound is treated with sodium methoxide in hot methanol. 2) The reaction of 6-chloropurine-2-amine (XIV) with 47% HI gives 6-iodopurine-2-amine (XV), which is condensed with [1S-(1alpha,2beta,3beta)]-3-(trifluoromethylsulfonyloxy)cyclobutane-1,2-dimethanol 1,2-dibenzoate (XVI) (obtained by treatment of the previously described cyclobutanol [X] with trifluromethanesulfonyl anhydride [Tf2O]) by means of benzyltriethylammonium hydroxide and pyridine in dichloromethane to afford the condensed iodopurine (XVII). The reaction of (XVII) with sodium methoxide hydrolyzes the benzoyl groups affording the 6-O-methylguanine derivative (XVIII), which is finally treated with aqueous HCl at 95 C.

合成路线20

4) The acylation of 4(S)-benzyloxazolidin-2-one (XXIV) with 4-pentenoyl pivaloyl anhydride (XXV) by means of NaH in THF gives 4(S)-benzyl-3-(4-pentenoyl)oxazolidin-2-one (XXVI), which is submitted to a diastereoselective syn aldol condensation with acrolein (XXVII), using dibutylboron triflate as catalyst, affording the aldol (XXVIII). The cyclization of (XXVIII) by means of the Grubbs catalyst in dichloromethane yields the cyclopentenol (XXIX), which is reduced with LiBH4 in THF/methanol to give the key intermediate 5(R)-(hydroxymethyl)-2-cyclopenten-1(R)-ol (XXX). The reaction of (XXX) with methyl chloroformate/pyridine/DMAP or methyl chloroformate/triethylamine/DMAP or acetic anhydride gives the diols (XXXI), (XXXII) and (XXXIII), respectively, each of which coupled with 2-amino-6-chloropurine (XXXIV) in the presence of NaH and palladium tetrakis(triphenylphosphine) in THF/DMSO, affords the purine intermediate (IX) already reported.

合成路线21

A new solid phase synthesis of abacavir has been reported: Condensation of the chiral 4(R)-benzyl-3-(4-pentenoyl)oxazolidin-2-thione (I) with acrolein (II) by means of TiCl4 and DIEA gives the adduct (III), which was transformed into the chiral cyclopentene (IV) by catalytic ring-closing metathesis. The reductive removal of the chiral auxiliary with LiBH4 affords the chiral diol (V), which is selectively silylated with TBDMSCl providing the primary silyl ether (VI). Acylation of the secondary alcohol of (VI) with benzoic anhydride gives the benzoate (VII), which is desilylated with HF in acetonitrile yielding the allylic benzoate (VIII). Benzoate (VIII) is condensed with a p-nitrophenyl Wang carbonate resin (IX) by means of DIEA and DMAP affording the solid phase resin (X) which is condensed with 2-amino-6-chloropurine (XI) by means of a Pd catalyst furnishing the adduct (XII). Thermal condensation of (XII) with cyclopropylamine (XIII) yields the diaminopurine resin (XIV) which, after cleavage from the resin by a treatment with TFA in dichloromethane, gives directly abacavir.

合成路线22

An efficient asymmetric synthesis of abacavir has been reported: Acylation of the chiral oxazolidinone (I) with the mixed anhydride (II) by means of BuLi in THF gives the N-pentenoyloxazolidinone (III), which by condensation with acrolein (IV) catalyzed by TiCl4 and (­)-spartein in dichloromethane yields the chiral adduct (V). The ring-closing metathesis of adduct (V) by means of the ruthenium catalyst (Cy3P)Cl2Ru=CHPh in dichloromethane affords the chiral cyclopentenol (VI), which is reduced to 5(R)-(hydroxymethyl)-2-cyclopenten-1(R)-ol (VII) by means of LiBH4 in THF. Reaction of diol (VII) with a) Ac2O, TEA and DMAP, b) methyl chloroformate, TEA and DMAP or c) methyl chloroformate, pyridine and DMAP gives a) the diacetate (VIII), b) the cyclic carbonate (IX) or c) the dicarbonate (X), respectively. The condensation of diacetate (VIII), cyclic carbonate (IX) or dicarbonate (X) with 2-amino-6-chloropurine (XI) by means of Pd(PPh3)4 yields the carbocyclic purines (XII), (XIII) or (XIV), respectively. Treatment of these chloro-purines (XII), (XIII) and (XIV) with cyclopropylamine (XV) in hot DMSO provides the corresponding cyclopropylaminopurine carbonate (XVI), abacavir or cyclopropylaminopurine acetate (XVII), respectively. Finally, the protecting groups of purines (XVI) and (XVII) are hydrolyzed with aqueous NaOH.

合成路线23

Alternatively, 2-amino-6-chloropurine (XI) is treated with cyclopropylamine (XV) in hot DMSO to give 2-amino-6-(cyclopropylamino)purine (XVIII), which is condensed with the chiral diacetate (VIII) by means of Pd(PPh3)4 to yield the carbocyclic purine acetate (XVI). Finally, purine (XVI) is deprotected by hydrolysis with aqueous NaOH.

合成路线24

The selective hydrolysis of the ester group of the chiral cyclopropafuranone (I) with an excess of NaOH, followed by ring closing with HCl, gives the carboxylic acid (II), which is treated with ethyl chloroformate and TEA in THF to yield the mixed anhydride (III). The reduction of the anhydride group of (III) with NaBH4 in THF/water affords the chiral hydroxymethyl cyclopropafuranone (IV). Alternatively, the selective hydrolysis of the lactone group of (I) with 1 equivalent of NaOH provides the malonic hemiester hemi sodium salt (V), which is reduced with NaBH4 and cyclized with conc. HCl to give the already reported hydroxymethyl cyclopropafuranone (IV). The reaction of (IV) with Ms-Cl and TEA or with SOCl2 and TEA yields the mesyloxymethyl (VI) or the chloromethyl (VII) compounds, which are condensed with 2-amino-6-chloropurine (VIII) by means of K2CO3 in hot DMF to afford the adduct (IX). The hydrolysis of the chlorine atom of (IX) by means of HCOOH at 100 C provides the guanine derivative (X). Finally, the lactone group of (X) is reduced with NaBH4 in hot ethanol to give the target cyclopropane nucleoside.

合成路线25

The reaction of 6-chloropurine-2-amine (I) with methanol and NaH gives 6-O-methylguanine (II), which is mixed with uracil arabinoside (III), purine nucleoside phosphorylase and uridine phosphorylase and submitted to incubation in a potassium phosphate solution at 37 C. After 26 days of incubation, the target compound is isolated.

合成路线26

The precursor (R)-9-[4-hydroxy-2-(hydroxymethyl)]guanine (VI) was prepared by conjugate addition of dimethyl itaconate (II) to 2-amino-6-chloropurine (I), followed by reduction of the resultant diester (III) with LiBH4 to yield (IV). Subsequent displacement of the 6-chloro group of (IV) with ammonia under pressure furnished the racemic 2,6-diaminopurine (V). Then, enantioselective deamination of (V) in the presence of adenosine deaminase provided the target (R)-guanine derivative (VI). Esterification of the 4-hydroxy group of (VI) with N-Boc-L-valine (VII) by means of DCC gave the valine ester (VIII). The remaining free hydroxyl group of (VIII) was further esterified with stearoyl chloride (IX) in pyridine, yielding stearate (X). Finally, acid-promoted N-Boc group cleavage in (IX) furnished the title compound.

合成路线27

In a different protection strategy, (diethoxyethyl)malonate (XIX) was obtained by alkylation of diethyl malonate (XVII) with bromoacetaldehyde diethyl acetal (XVIII). Reduction of the ester groups of (XIX) with LiBH4 provided diol (XX). The asymmetric mono-acetate ester (XXI) was generated by enantioselective acylation of the prochiral diol (XX) with vinyl acetate in the presence of lipase PS 30. Reaction of the free hydroxyl of (XXI) with p-toluenesulfonyl chloride afforded tosylate (XXII), which was subsequently condensed with 2-amino-6-chloropurine (I), yielding adduct (XXIII). Conversion of the chloropurine ring of (XXIII) to the target guanine derivative (XXV) was achieved by displacement of the chloro group with benzyl alcohol, with concomitant acetate ester hydrolysis, followed by hydrogenolytic cleavage of the resultant benzyl ether (XXIV). Alternatively, initial acetate ester hydrolysis in (XXIII) gave alcohol (XXVI), which was further subjected to chloro group hydrolysis in the presence of either KOH or tertiary amines to yield (XXV). Conversion of alcohol (XXV) to the target stearate ester (XXVIII) was achieved by treatment with stearoyl chloride (IX) or with the mixed anhydride of stearic acid (XXVII) with pivaloyl chloride or with tosyl chloride.

合成路线28

In a further procedure, the prochiral diol (XX) was converted to the asymmetric mono-stearate ester (XXXII) employing vinyl stearate (XXXI) and lipase PS 30. After tosylation of alcohol (XXXII), the resulting diethoxy acetal (XXXIII) was hydrolyzed to aldehyde (XXXIV) employing different acidic catalysts. Reduction of aldehyde (XXXIV) to the corresponding alcohol (XXXV) was effected by means of catalytic hydrogenation over Ra-Ni or borane-tert-butylamine complex. Alcohol (XXXV) was further condensed with N-Cbz-L-valine (XVI), producing the diester tosylate (XXXVI). The analogous N-Boc- and N-Alloc-protected valine esters were similarly prepared. 6-Benzyloxy-2-aminopurine (XXXVII) was prepared by treatment of chloropurine (I) with benzyl alcohol and NaH or NaOH. Alkylation of purine (XXXVII) with tosylate (XXXVI) furnished adduct (XXXVIII), which was finally deprotected by catalytic hydrogenation. Optionally, tosylate (XXXVI) was condensed with chloropurine (I) to give (XXXIX). Hydrolysis of the chloropurine ring of (XXXIX) to the guanine derivative (XIII) employing either Et3N or HOAc, followed by catalytic hydrogenation as above, provided an alternative access to the title compound.

合成路线29

A related strategy required previous conversion of chloropurine (I) to the iodopurine (XL), which was effected by means of HI. Alkylation of purine (XL) with tosylate (XXXVI) provided (XLI), which was hydrolyzed to the guanine (XIII) using NaOAc/HOAc.

合成路线30

(S)-5-(Hydroxymethyl)tetrahydrofuran-2-one (I) was converted into bromide (II) by reaction with CBr4 and PPh3. Subsequent reduction of the lactone with DIBAL-H in toluene at -78 C, followed by acetylation of the resulting lactol (III) with Ac2O and pyridine, afforded acetate (IV) as a 1:1 mixture of isomers cis and trans. The phosphonate group was then introduced by a TiCl4-catalyzed Arbuzov reaction with triethyl phosphite at low temperature, to give a mixture of geometric isomers, from which the desired cis compound (V) was isolated by column chromatography. Condensation of this bromide with 2-amino-6-chloropurine (VI) in the presence of Cs2CO3 in DMF gave (VII). The phosphonate ester was hydrolyzed by treatment with excess Me3SiBr to produce an intermediate trimethylsilyl ester, and then the target compound was obtained by simultaneous hydrolysis of the silyl ester to phosphonic acid and the 6-chloropurine group to guanine in boiling water, followed by conversion to the corresponding ammonium salt with NH4OH.

合成路线31

(S)-5-(Hydroxymethyl)tetrahydrofuran-2-one (I) was converted into bromide (II) by reaction with CBr4 and PPh3. Subsequent reduction of the lactone with DIBAL-H in toluene at -78 C, followed by acetylation of the resulting lactol (III) with Ac2O and pyridine, afforded acetate (IV) as a 1:1 mixture of isomers cis and trans. The phosphonate group was then introduced by a TiCl4-catalyzed Arbuzov reaction with triethyl phosphite at low temperature, to give a mixture of geometric isomers, from which the desired cis compound (V) was isolated by column chromatography. Condensation of this bromide with 2-amino-6-chloropurine (VI) in the presence of Cs2CO3 in DMF gave (VII). The phosphonate ester was hydrolyzed by treatment with excess Me3SiBr to produce an intermediate trimethylsilyl ester, and then the target compound was obtained by simultaneous hydrolysis of the silyl ester to phosphonic acid and the 6-chloropurine group to guanine in boiling water, followed by conversion to the corresponding ammonium salt with NH4OH.

合成路线32

Alkylation of 2-amino-6-chloropurine (I) with tosylate (II) afforded the phosphonomethoxyethyl purine (III). Subsequent displacement of the chloro atom of (III) by cyclopropylamine (IV) furnished diaminopurine (V). The isopropyl protecting groups of (IV) were finally cleaved by treatment with bromotrimethylsilane.

合成路线33

In an alternative method for preparing precursor (V), 2-amino-6-chloropurine (I) was first treated with cyclopropylamine (IV) to give diaminopurine (VI), and then alkylated with tosylate (II).

合成路线34

Treatment of diol (I) with 1,1'-carbonyldiimidazole produced the cyclic carbonate (II). Cleavage of the O-benzyl group of (II) by hydrogenolysis over Pd/C, gave alcohol (III), which was converted to mesylate (IV) by means of MsCl and Et3N. Subsequent coupling of (IV) with 2-amino-6-chloropurine (V) produced the 9-alkylated derivative (VI). The chlorine atom of (VI) was then removed by hydrogenolysis in the presence of Pd/C and Et3N to furnish (VII). Finally, opening of the cyclic carbonate group of (VII) with isopropanol upon heating in the presence of silica gel yielded the target compound.

合成路线35

The reaction of monolabeled diethyl malonate (I) with 2-benzyloxyethyl bromide (II) by means of NaH in refluxing THF gives the corresponding benzyloxyethyl derivative (III), which is reduced with LiAlH4 in ethyl ether yielding the diol (IV). The protection of (IV) by reaction with 2,2-dimethoxypropane (V) and p-toluenesulfonic acid affords the 1,3-dioxane (VI), which is debenzylated with H2 over Pd/C in THF giving the alcohol (VII). The reaction of (VII) with CBr4 and PPh3 in DMF yields the bromide (VIII), which is condensed with the purine (IX) by means of K2CO3 in DMF affording the expected purin-9-yl derivative (X). The hydrolysis of the 1,3-dioxane group with AcOH /water gives the diol (XI), which is monoacylated with isopropyl chloroformate (XII) by means of cool pyridine yielding the mixture of regioisomers (XIII), (XIV). Finally, this mixture is dechlorinated with ammonium formate over Pd/C in refluxing methanol afffording the target compound also as a mixture of regioisomers.

合成路线36

(S)-Glycidol (I) was selectively opened by Li2NiBr4 at 0 C to provide (S)-3-bromo-1,2-propanediol (II). Subsequent reaction of (II) with trimethyl orthoformate in the presence of p-toluenesulfonic acid generated the dioxolane (III) as a 1:1 mixture of cis and trans orthoesters. The methoxy orthoester (III) was further converted to the isopropoxy analogue (IV) by treatement with isopropanol under acidic conditions. Introduction of the phosphonate group in (IV) was achieved by means of a ZnCl2-catalyzed Arbuzov reaction with triisopropyl phosphite and phosphorus trichloride to give a 2:5 mixture of cis (V) and trans (VI) phosphonates, which were separated by flash chromatography. Displacement of cis bromide (V) with 2-amino-6-chloropurine (VII) in the presence of Cs2CO3 in DMF at 60 C provided compound (VIII). The phosphonate ester of (VIII) was then deprotected by treatment with ISiMe3, followed by aqueous hydrolysis of the intermediate silyl phosphonate (IX) and concomitant hydrolysis of the 6-chloropurine to guanine (X). Finally, absorption on a Sephadex DEAE A-25 column, followed by elution with ammonium bicarbonate solution, provided the title ammonium salt.

合成路线37

The reaction of 2-amino-6-chloropurine (I) with 1,4-diazabicyclo[2.2.2]octane (II) in DMSO gives 1-(2-aminopurin-6-yl)-4-aza-1-azoniabicyclo[2.2.2]octane chloride (II), which is condensed with cyclohexylmethanol (III) by means of NaH in DMSO.

合成路线38

Alkylation of 2-amino-6-chloropurine (I) with 2-methoxybenzyl chloride (II) in the presence of K2CO3 and Bu4NI gives the 9-substituted purine (III). Amino purine (III) is converted into the corresponding 2-iodo derivative (IV) by treatment with isoamyl nitrite in hot diiodomethane. Finally, displacement of the 6-chloro group of (IV) with methylamine furnishes the desired adenine derivative.

合成路线39

Coupling of known allylic alcohol (I) with 2-amino-6-chloropurine (II) under Mitsunobu conditions furnished nucleoside (III). Subsequent desilylation and chloride hydrolysis by means of aqueous trifluoroacetic acid yielded the title compound.

合成路线40

Regiospecific opening of the chiral 2-(benzyloxymethyl)oxirane (I) with lithiated diethyl methylphosphonate in the presence of boron trifluoride etherate afforded phosphonate (III). After conversion of (III) to the chloromethyl ether (IV), upon treatment with paraformaldehyde and HCl, condensation with the sodium salt of 2-amino-6-chloropurine (V) gave the nucleoside phosphonate (VI). Simultaneous hydrogenolysis of the chlorine atom and benzyl ether of (VI) by transfer hydrogenation in the presence of ammonium formate and Pd/C yielded (VII). Finally, the phosphonate ester groups of (VII) were cleaved by means of bromotrimethylsilane.

合成路线41

Regiospecific opening of the chiral 2-(benzyloxymethyl)oxirane (I) with lithiated diethyl methylphosphonate in the presence of boron trifluoride etherate afforded phosphonate (III). After conversion of (III) to the chloromethyl ether (IV), upon treatment with paraformaldehyde and HCl, condensation with the sodium salt of 2-amino-6-chloropurine (V) gave the nucleoside phosphonate (VI). Simultaneous hydrogenolysis of the chlorine atom and benzyl ether of (VI) by transfer hydrogenation in the presence of ammonium formate and Pd/C yielded (VII). The phosphonate ester groups of (VII) were then cleaved by means of bromotrimethylsilane to give phosphonic acid (VIII). Finally, intramolecular cyclization of (VIII) by treatment with DCC furnished the title compound.

合成路线42

Selective hydrolysis of the methyl esters (III) with LiOH provides the desired cis-dioxolane acid (IX) and the corresponding trans isomer (VIII), which are separated by column chromatography. Alternatively, ester (III) is subjected to enzymatic resolution with several different enzymes to provide a mixture of the undesired trans-dioxolane acid (VIII) and the unreacted cis-ester (X), separable by partition between H2O and EtOAc. The desired cis-ester (X) is then hydrolyzed with LiOH to the carboxylic acid (IX). Oxidative decarboxylation of acid (IX) employing lead tetraacetate furnishes the acetoxy dioxolane (XI). After silylation of 2-amino-6-chloropurine (XII) with hexamethyldisilazane in the presence of ammonium sulfate, coupling with the acetoxy dioxolane (XI), promoted by either trimethylsilyl triflate or by iodotrimethylsilane, gives rise to an anomeric mixture of adducts (XIII). Following chromatographic isolation of the target cis-anomer, chloride displacement with cyclopropylamine yields the diamino purine derivative (XIV). The benzoate ester group of (XIV) is finally hydrolyzed to the title compound by means of methanolic ammonia.

合成路线43

Phosphonate (III) was prepared by the Michaelis-Arbuzov reaction by heating a mixture of 2-chloroethyl chloromethyl ether (I) and tris(2,2,2-trifluoroethyl)phosphite (II) at 160 C. The chloroethoxy derivative (III) was then converted to the corresponding iodide (IV) by treatment with NaI under Finkelstein reaction conditions. Alkylation of 2-amino-6-chloropurine (V) with iodide (IV) in the presence of DBU furnished the phosphonyl purine (VI). The 6-chloro group of (VI) was finally displaced with p-methoxythiophenol (VII) in hot DMF, yielding the target thioether.

合成路线44

2-Amino-6-chloropurine (I) is converted into the 2-fluoro analogue (II) by diazotization in the presence of fluoroboric acid. Subsequent alkylation of (II) with EtOH under Mitsunobu conditions provides the 9-ethyl purine (III).

合成路线45

The condensation between mesylate (I) and 2-amino-6-chloropurine (II) in the presence of Cs2CO3 affords nucleoside (III). Hydrolysis of (III) with trimethylsilyl bromide, followed by refluxing with HCl, provides the target phosphonic acid, which is finally isolated as the corresponding ammonium salt.

合成路线46

Reaction of 1,2:5,6-di-O-isopropylidene-3-O-tosyl-a-D-allofuranose (I) with KF in acetamide at 210 oC gives 3-deoxy-3-fluoro-1,2:5,6-di-O-isopropylidene-a-D-glucofuranose (II), which is treated with a 1:1 mixture of metha-nol and 0.7% aqueous H2SO4 to yield 3-deoxy-3-fluoro-1,2-isopropylidene-a-D-glucofuranose (III). Selective acylation of the sugar (III) with benzoyl chloride in pyridine affords the 6-O-benzoyl derivative (IV), which is treated with Amberlite IR-100 (H+) ion-exchange resin in hot dioxane to provide 6-O-benzoyl-3-deoxy-3-fluoro-D-glucofuranose (V). The oxidative cleavage of glucofuranose (V) by means of KIO4 in water results in rearrangement to give 5-O-benzoyl-2-deoxy-2-fluoro-3-O-formyl-D- arabinofuranose (VI), which is deformylated by means of NaOMe in methanol to provide 5-O-benzoyl-2-deoxy-2-fluoro-D-arabinofuranose (VII). Acylation of the arabinofuranose (VII) with acetic anhydride in pyridine affords the 1,3-di-O-acetyl derivative (VIII), which is treated with HBr in AcOH/CH2Cl2 to yield 3-O-acetyl-5-O-benzoyl-2-deoxy-2-fluoro-D-arabinofuranosyl bromide (IX) (1). Condensation of compound (IX) with 2-chloroadenine (X) by means of potassium tert-butoxide in different solvents gives the acylated 2-chloroadenosine derivative (XI), which is finally deacylated by means of NaOMe in methanol.

合成路线47

合成路线48