The reaction of the chiral epoxide (I) with isobutylamine (II) in refluxing ethanol gives the secondary amine (III), which is protected with benzyl chloroformate (IV) and TEA, yielding the dicarbamate (V). Selective deprotection of (V) with dry HCl in ethyl acetate affords the primary amine (VI), which is treated with 3(S)-tetrahydrofuryl N-succinimidinyl carbonate (VII) (prepared by condensation of tetrahydrofuran-3(S)-ol (VIII) with phosgene and N-hydroxysuccinimide (IX)) and DIEA in acetonitrile to provide the corresponding carbamate (X). The deprotection of (X) by hydrogenation with H2 over Pd/C in ethanol gives the secondary amine (XI), which is condensed with 4-nitrophenylsulfonyl chloride (XII) by means of NaHCO3 in dichloromethane/water to yield the sulfonamide (XIII). Finally, the nitro group of (XIII) is reduced with H2 over Pd/C in ethyl acetate to afford the target compound.
The reaction of the chiral epoxide (I) with isobutylamine (II) in refluxing ethanol gives the secondary amine (III), which is protected with benzyl chloroformate (IV) and TEA, yielding dicarbamate (V). Selective deprotection of (V) with dry HCl in ethyl acetate affords the primary amine (VI), which is treated with 3(S)-tetrahydrofuryl N-succinimidinyl carbonate (VII) -- obtained by reaction of tetrahydrofuran-3(S)-ol (VIII) first with phosgene and then with N-hydroxysuccinimide (IX) -- and DIEA in acetonitrile to provide the corresponding carbamate (X). Deprotection of (X) by hydrogenation with H2 over Pd/C in ethanol gives the secondary amine (XI), which is condensed with 4-nitrophenylsulfonyl chloride (XII) by means of NaHCO3 in dichloromethane/water to yield the sulfonamide intermediate (XIII).
Esterification of the OH group of compound (XIII) with PO3H3 by means of DCC in hot pyridine gives the corresponding phosphite (XVII), which is oxidized with bis(trimethylsilyl)peroxide in bis(trimethylsilyl)azane to yield the expected phosphate (XVIII). Reduction of the nitro group of (XVIII) with H2 over Pd/C in ethyl acetate affords fosamprenavir (XIX). Finally, fosamprenavir (XIX) is treated with aqueous NaHCO3 or with calcium acetate in water to provide the corresponding salts. Alternatively, the phosphate (XIX) can be obtained directly by reaction of intermediate (XIII) with POCl3 in pyridine, followed by hydrolysis with 2N HCl.
Reaction of the chiral epoxide (I) with isobutylamine (II) in refluxing ethanol gives the secondary amine (III), which is condensed with 4-nitrophenylsulfonyl chloride (IV) and TEA in hot toluene to yield the sulfonamide (V). Deprotection of (V) with HCl hot toluene/water affords the primary amine (VI), which is condensed with imidazole-1-carboxylic acid 3(S)-tetrahydrofuryl ester (VII) [prepared by reaction of tetrahydrofuran-3(S)-ol (VIII) with carbonyldiimidazole (CDI) in ethyl acetate] to provide the corresponding carbamate (IX). Finally, the nitro group of (IX) is reduced with H2 over Pd/C in ethyl acetate to afford the target compound.
The reaction of the chiral epoxide (I) with isobutylamine (II) in refluxing ethanol gives the secondary amine (III), which is condensed with 4-nitrophenylsulfonyl chloride (XII) and TEA in hot toluene, yielding sulfonamide (XIV). Deprotection of (XIV) with HCl in hot toluene/water affords the primary amine (XV), which is condensed with imidazole-1-carboxylic acid 3(S)-tetrahydrofuryl ester (XVI) -- prepared by reaction of tetrahydrofuran-3(S)-ol (VIII) with carbonyldiimidazole (CDI) in ethyl acetate -- to provide intermediate (XIII).