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Synthesis 1990; 1990(7): 550-556
DOI: 10.1055/s-1990-26936
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Optically Pure (S)-6,7-Dimethoxy-1,2,3,4-Tetrahydro-3-Isoquinolinecarboxylic Acid and Asymmetric Hydrogenation Studies Related to Its Preparation

N. J. O'Reilly* , W. S. Derwin, H. C. Lin
  • *Occidental Chemical Corporation, Technology Center, 2801 Long Rd., Grand Island, NY-14072, USA
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Publication Date:
17 September 2002 (online)

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(S)-6,7-Dimethoxy-1,2,3,4-tetrahydro-3-isoquinolinecarboxylic acid has been prepared in optically pure form as its hydrochloride. Pictet-Spengler ring closure of the optically pure (S)-2-amino-3-(3,4-dimethoxyphenyl)propanoic acid hydrochloride salt (L-3,4-dimethoxyphenylalanine hydrochloride) proceeded without significant racemization. A simple and safe, asymmetric hydrogenation catalyst system has been developed which allows the rapid screening of various chiral phosphine ligands via an in situ ionic complex. A protocol was demonstrated which uses a statistical approach to consider the effects of changes in solvent, nitrogen substituent, oxygen substituent, and ligand in the asymmetric hydrogenation of alkyl or aryl (Z)-2-acylamino-3-(3,4-dimethoxyphenyl)-2-propenoate derivatives. This method was used to successfully determine the optimal substrate and conditions for the preparation of enantiomerically pure (S)-2-amino-3-(3, 4-dimethoxyphenyl)propanoic acid hydrochloride salt.

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