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Synlett 1991; 1991(3): 193-194
DOI: 10.1055/s-1991-20676
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Practical Asymmetric Synthesis of (R)-(-)-Carnitine Catalyzed by (2R,4R)-4-(Dicyclohexylphosphino)-2-(di-3,5-xylylphosphinomethyl)-N-methyl-1-pyrrolidinecarboxamide-Rhodium Complex1

Hideo Takeda* , Shigeki Hosokawa, Masakazu Aburatani, Kazuo Achiwa
  • *Research Division, Fuji Chemical Industries, Ltd., 530 Chokeiji, Takaoka 933, Japan
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Publication Date:
07 March 2002 (online)

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The chiral pyrrolidinebisphosphine ligands, MCCXM 1 [4- (dicyclohexylphosphino) -2- (di-3,5 - xylylphosphinomethyl) - N-methyl-1-pyrrolidinecarboxamide] and MCCPM 2 (4-(dicyclohexylphosphino)-2-(diphenylphosphinomethyl) -N-methyl-1-pyrrolidinecarboxamide], were prepared. Their rhodium complexes were found to be practical catalysts for the asymmetric hydrogenation of ethyl 4-(dimethylamino)-3-oxobutanoate (3) to give (R)-(-)-norcarnitine (4). By reaction with methyl iodide, 4 was readily converted into (R)-(-)-carnitine (3-carboxy-2-hydroxy-N,N,N-trimethyl-1-propanaminium hydroxide, inner salt) and its optical purity was found to be 85% ee when MCCXM-rhodium complex was used as the catalyst. The absolute stereochemistry of the hydrogenation product was also discussed.

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