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).

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).

The reaction of N,N-dibenzyl-L-alaninal (I) with nitromethane, catalyzed by the chiral ammonium salt (II) and KF in THF gives the chiral nitroalcohol (III), which is reduced with NiCl2 and NaBH4 to yield the aminoalcohol (IV). The condensation of (IV) with isobutyraldehyde (V) affords the Schiff base (VI), which is reduced with NaBH4 to provide the secondary amine (VII). The reaction of (VII) with 4-nitrobenzenesulfonyl chloride (VIII) and TEA in dichloromethane furnishes the sulfonamide (IX), which is deprotected by hydrogenation with H2 over Pd/C in methanol, giving the diamino compound (X). Finally, this compound is condensed with 3(S)-tetrahydrofuryl (N-oxysuccinimidyl) carbonate (XI) by means of TEA in dichloromethane to afford the target carbamate.