Chemical and Pharmaceutical Bulletin
Online ISSN : 1347-5223
Print ISSN : 0009-2363
ISSN-L : 0009-2363
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Racemization Kinetics of Meluadrine Tartrate in Aqueous Solution
Kazuya MATSUOYouichi YAMAMOTONoriyuki KADOMasahiro YAMAZAKIOsamu NAGATAHideo KATOAkira TSUJI
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2001 Volume 49 Issue 1 Pages 101-104

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Abstract

The kinetics of racemization of meluadrine tartrate in aqueous solution was investigated by HPLC, over the pH range of 1.2 to 12 at 40, 60 and 80 °C. The racemization was followed by measuring both the residual (R)-enantiomer and formed (S)-enantiomer of meluadrine. The pH-racemization rate profile of meluadrine showed a minimum racemization rate constant between pH 4 and 6, and the rate constant increased rapidly with decreasing pH below pH 3. In the basic region, the racemization rate constant showed a maximum at around pH 9. Four pathways of racemization of meluadrine are proposed, depending on the dissociation state of the phenolic and amino groups. The calculated racemization rate-pH profile agreed well with the observations. The values of activation energy (95-115 kJ/mol) suggest that a similar quinoid intermediate is involved throughout the pH range examined. The objective of this study is to clarify the racemization mechanism of benzylalcohol derivative with phenoric group. This study offers fundamental knowledge for the other benzylalcohol derivatives, which have similar moiety structure.

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© 2001 The Pharmaceutical Society of Japan
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