The condensation of N2-acetylguanine (VIII) with (V) by means of ammonium sulfate in refluxing HMDS gives (VII). This compound is deprotected by a treatment with palladium hydroxide in refluxing cyclohexane.
The reaction of epichlorohydrin (I) with benzyl alcohol (II) by means of NaOH in water gives 1,3-di-O-benzylglycerol (III), which is condensed with paraformaldehyde by means of HCl in methylene chloride to yield 1,3-di-O-benzyl-2-O-(chloromethyl)glycerol (IV). Acetylation of (IV) with potassium acetate in acetone affords 1,3-di-O-benzyl-2-O-(acetoxymethyl)glycerol (V), which is condensed with diacetylguanine (VI) by means of p-toluenesulfonic acid in sulfolane giving N2-acetyl-9-[[1,3-bis(benzyloxy)-2-propoxy]methyl]guanine (VII). Finally, this compound is deprotected by a treatment with palladium hydroxide in refluxing cyclohexane.
The condensation of 6-chloroguanine (IX) with (V) by means of ammonium sulfate in refluxing HMDS gives 9-[[1,3-bis(benzyloxy)-2-propoxy]methyl]-6-chloroguanine (XI), which is treated with sodium methoxide and mercaptoethanol in refluxing methanol to yield 9-[[1,3-bisbenzyloxy)-2-propoxy]methyl]guanine (XI), which is finally deprotected by a treatment with palladium hydroxide in refluxing cyclohexane.
The acetylation of 4-hydroxymethyl-1,3-dioxolane (XII) gives the corresponding acetate (XIII), which by reaction with acetic anhydride and ZnCl2 is converted to 1,3-diacetoxy-2-(acetoxymethoxy)propane (XIV). The condensation of (XIV) with diacetylguanine (VI) by means of ethanesulfonic acid (B) yields the triacetoxy precursor (XV), which is hydrolyzed with aqueous methylamine.
The condensation of diacetyl guanine (I) with 1,3-diacetoxy-2-(acetoxymethoxy)propane (II) by means of TsOH in hot DMF gives the target intermediate, N2-acetyl-9-[2-acetoxy-1-(acetoxymethyl)ethoxymethyl]guanine (III). (see Synthline Scheme no. 11147104a, intermediate no. (XV)).
The acetylation of guanine (I) or guanosine (II) with acetic anhydride gives the diacetyl guanine (III), which is condensed with 1,4-diacetoxy-2-oxabutane (IV) by means of TsOH to yield N,O-diacetyl acyclovir (V). Finally, this compound is deacetylated with NH3, NaOH or pyrrolidine at room temperature, or also with refluxing glycol.
The reaction of 1,3-dichloro-2-propanol (I) with Bn-ONa gives 1,3-dibenzyloxy-2-propanol (II), which by reaction with paraformaldehyde and HCl is converted into the chloromethyl ether (III). The reaction of (III) with potassium acetate affords the acetoxymethyl ether (IV), which is condensed with diacetylguanine (V) by means of TsOH to provide fully protected ganciclovir (VI). Finally, this compound is debenzylated to (VII) with Pd(OH)2/cyclohexene and deacetylated with ammonia in methanol.
The reaction of 4-(chloromethyl)-1,3-dioxolane (I) with Ac2O, HOAc and ZnCl2 gives the diacetoxy compound (II), which is treated with KOAc to yield the triacetoxy compound (III). The condensation of (III) with diacetyl guanine (IV) by means of ethylsulfonic acid affords the triacetyl ganciclovir (V), which is finally deacetylated with methylamine in methanol.