Efficient synthesis and practical resolution of 1-(naphthalen-1-yl) ethanamine, a key intermediate for cinacalcet
An efficient synthesis of 1-(naphthalen-1-yl)ethanamine (RS-2) and its practical resolution to optically pure (1R)-(naphthalen-1-yl)ethanamine (R-(+)-2), a key intermediate in the synthesis of cinacalcet hydrochloride (1), is described. The resolution of RS-2 using R-(-)-mandelic acid as a resolving agent in ethanol was established on an industrial scale to give pure R-(+)-2 with >99.8% ee after liberation of the amine from its mandelate salt. An efficient process for the racemization of undesired isomer S-(-)-2 is also provided to maximize the yield of desired enantiomer.
PROCESS FOR THE PREPARATION OF CINACALCET AND SALTS THEREOF, AND INTERMEDIATES FOR USE IN THE PROCESS
There is provided a process for preparing a salt of the (R)- or (S)-isomer of 1- naphthylethylamine with mandelic acid or a derivative thereof, the process comprising reacting racemic 1-naphthylethylamine with mandelic acid or a derivative thereof to obtain the (R)- or (S)-isomer of 1-naphthylethylamine salt (III) with the acid. The salts also form an aspect of the present invention. There is also provided a salt of the (R)- or (S)-isomer of 1-naphthylethylamine with mandelic acid or a derivative thereof. There is also provided a process for preparing cinacalcet (I) or a salt thereof, the process comprising reacting an ester (II) with (R)-i-naphthylethylamine or a salt of (R)-i-naphthylethylamine and mandelic acid or a derivative thereof, to obtain cinacalcet, and optionally converting the cincalcet to a salt thereof.
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(2010/09/18)
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