Main > PNEUMOLOGY > Asthma > Treatment > Montelukast. (LTRA) > Co.: USA. M (Brand Form./Patents) > Synthesis

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is an example of asymmetric amplification on an industrial scale. It is similar to a compound called L-699,392. Co. s researchers tried to develop an efficient synthesis for this compound in the early 1990s. L-699,392 s S chiral center is created by reduction of a prochiral ketone with a borane-(–)--pinene reagent. A reagent prepared from 98% optically pure (–)--pinene gives a product ee of 97%. But a reagent prepared from less expensive 70% optically pure (–)--pinene yields a product ee of 95%, which can be pushed to >99.5% by using an excess. With (+)-a-pinene, reduction of the ketone and subsequent workup gives the R chiral center in drug


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