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Synthesis of enantiopure (R)-2-(4-methoxy-3-(3-methoxypropoxy)-benzyl)-3-methylbutanoic acid—a key intermediate for the preparation of Aliskiren

✍ Scribed by Natalia Andrushko; Vasyl Andrushko; Thomas Thyrann; Gerd König; Armin Börner

Publisher
Elsevier Science
Year
2008
Tongue
French
Weight
184 KB
Volume
49
Category
Article
ISSN
0040-4039

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✦ Synopsis

The enantioselective hydrogenation of (E)-2-(4-methoxy-3-(3-methoxypropoxy)-benzylidene)-3-methylbutanoic acid (1) to (R)-2-(4-methoxy-3-(3-methoxypropoxy)-benzyl)-3-methylbutanoic acid (2)-a key intermediate in the synthesis of the pharmacologically important renin inhibitor Aliskiren-is described. The stereochemistry of the catalytic transformation has been studied using a number of homogeneous chiral Rh(I) and Ru(II) complexes bearing ferrocene-based phosphine ligands. The highest enantioselectivity for the homogeneous hydrogenation of 1 (up to 95% ee) was achieved with a [Rh(NBD) 2 ]BF 4 pre-catalyst (substrate/catalyst ratio 100:1, 10 bar H 2 , 40 °C, in MeOH). To bring the enantioselectivity to perfection an effective method for the isolation of the enantiopure carboxylic acid is suggested likewise.

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