Direct isolution of optically pure (3S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid
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United States of America Patent
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Mar 11, 1997
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N/A
app pub date -
Mar 14, 1995
filing date -
Mar 14, 1995
priority date (Note) -
Expired
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Abstract
A substantially pure L-isomer of (3S) 1,2,3,4-tetrahydro-isoquinoline is produced from an optically enriched mixture by cyclizing D- or L-phenylalanine using a solution of formaldehyde and hydrochloric acid, adjusting the pH of the mixture to yield the neutral free acid form and treating the mixture with dilute acetic acid of from about 5.0 wt/wt % to about 25 wt/wt %. The mixture is then refluxed at 80.degree. C. to 95.degree. C. and cooled to about 10.degree. C. to yield amorphous powdery solid material.
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