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This alcohol is oxidized to aldehyde with NMMO and tetrapropylammonium perruthenate (TPAP), and further oxidized to carboxylic acid (XVIII) with KMnO4 and tetrabutylammonium bromide (TBAB). Coupling of (XVIII) with aminoamide (XIX) by means of diethyl cyanophosphonate and TEA gives (XX). Finally, acid hydrolysis of the oxazolidine ring and Boc protecting groups of (XX) furnishes the corresponding amino alcohol, which is finally converted to the hemifumarate salt.

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The reduction of the chiral propionic acid (VII) with NaBH4 in THF gives the primary alcohol (XXIX), which by reaction with SOCl2 and pyridine in CHCl3 yields the chloride (XXX). Condensation of (XXX) with the butyrolactone intermediate (XXVII) by means of Mg and dibromoethane affords the ketonic adduct (XXXI). Reduction of the exocyclic carbonyl group of (XXXI) with NaBH4 in THF/ methanol provides a 3:1 diastereomeric mixture of the desired chiral alcohol (XXXII) and its OH-epimer (XXXIII) that are separated by flash chromatography. Reaction of (XXXII) with MsCl and TEA, followed by treatment with NaN3, affords the azido derivative (XXXIV), which is condensed with 4-amino-3,3-dimethylbutyramide (XIX) by means of 2-hydroxypyridine and TEA to provide the adduct (XXXV). Finally, the azido group of (XXXV) is reduced with H2 over Pd/ in MeOH to yield the target amino alcohol. An extensive study on the stereoselective reduction of the ketonic adduct (XXXI) has been performed. No better diastereoselectivity than 3:1 has been obtained for the synthesis of the chiral alcohol (XXXII). However, excellent diastereoselectivity (97:3) has been obtained for the synthesis of its OH-epimer, alcohol (XXXIII), with K-selectride in THF, which could potentially provide access to the target amino alcohol via a double inversion protocol.

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Alternatively, the spiro aldehyde (XLVII) is treated with N-benzylhydroxylamine in dichloromethane to give nitrone (LII), which is submitted to a Grignard reaction with the magnesium derivative of intermediate (XXX) in THF to afford the adduct (LIII) as a mixture of epimers at the amino group. Simultaneous N-dehydroxylation and cleavage of the spiro function of (LIII) by means of Zn, Cu(OAc)2 in AcOH/water gives lactone (LIV), which is condensed with 3-amino-2,2-dimethylpropionamide (XIX) by means of TEA and 2-hydroxypyridine giving the adduct (LV). Finally, the benzylamino group of (LV) is removed with H2 over Pd/C in methanol to yield a mixture of two epimers at the amino group, from which aliskiren is separated.

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The cyclization of (XVII) by means of TsOH in refluxing methanol gives the chiral lactone (XVIII), which is condensed with 3-amino-2,2-dimethylpropionamide (XIX) by means of TEA and 2-hydroxypyridine at 90 C to yield the corresponding amide (XX). Finally, the azido group of (XX) is reduced with H2 over Pd/C in tert-butyl methyl ether to afford the target Aliskiren.

合成路线5

The condensation of the chiral chloro derivative (I) with 5-chloro-[2(S)-isopropyl]-4-pentanoic acid methyl ester (II) by means of Mg and dibromoethane in THF gives the chiral octenoic ester (III) which is converted to the corresponding acid (IV) by means of LiOH in THF/methanol/water. The reaction of (IV) with NBS in dichloromethane yields the bromolactone (V), which is treated with LiOH in isopropanol to yield the epoxide (VI). This compound, without isolation, is treated with HCl in the same solvent to afford the chiral hydroxylactone (VII). The reaction of the OH group of (VII) with MsCl and pyridine in toluene provides the mesylate (VIII), which is treated with NaN3 in hot 1,3-dimethylperhydropyrimidin-2-one to give the azido derivative (IX). The condensation of (IX) with 3-amino-2,2-dimethylpropionamide (X) by means of 2-hydroxypyridine in hot TEA yields the carboxamide (XI). Finally, the azido group of (XI) is reduced with H2 over Pd/C in tert-butyl methyl ether to provide the target Aliskiren.

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