Phenylpropanolamine → (+/-)-trans-1,2,4,5-Tetrahydro-4-methyl-7,8-methylenedioxy-5-oxo-3-benzothiepin-2-carboxylic acid

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Reaction Steps

In 5 mL of methanol was suspended 0.5 g of a racemic mixture, 1,2,4,5-tetrahydro-4-methyl-7,8-methylenedioxy-5-oxo-3-benzothiepin-2-carboxylic acid (content 99.5%; trans compound 88.1%, cis compound 11.4%). To the suspension was added 0.27 g (1 equivalent) of (1R,2S)-norephedrine, which was once made into a solution, followed by crystallization in about 5 minutes. Then, the crystals were aged for 30 minutes at room temperature (25° C.). The crystals were collected by filtration, washed with 5 mL of cold methanol and dried overnight at room temperature under reduced pressure to afford 0.25 g of substantially pure (2R,4S)-1,2,4,5-tetrahydro-4-methyl-7,8-methylenedioxy-5-oxo-3-benzothiepin-2-carboxylic acid.(1R,2S)-norephedrine salt as colorless crystals [HPLC area percentage: (2R,4R):(2S,4S):(2S,4R):(2R,4S)=0.7%:0%:3.7%:95.3%]

Provenance & Evidence