Abstract:The resolution of racemic 3-(methylamino)-1-(2-thienyl)propan-1-ol (3), a new key intermediate for duloxetine (1)

The molecular mechanism of dielectrically controlled resolution (DCR) observed in the resolution of (RS)-2methylpyrrolidine (1) by (R,R)-tartaric acid (2) was studied. (R)-1 and (S)-1 were preferentially resolved from water/ethanol mixed solvents of different compositions with ) 24.4 and 30, respectively. The X-ray analysis of two resolved salts, i.e., (R)-1:(R,R)-2 and (S)-1:(R,R)-2:H 2 O, was undertaken, and their crystal structures were compared in detail. The carboxyl groups of (R,R)-2 are engaged in strong negative-charge-assisted intermolecular hydrogen bonds, and (R,R)-2 forms similar layers in both crystal structures. The space between the layers in (S)-1:(R,R)-2:H 2 O is larger than that in (R)-1:(R,R)-2. (R)-1 and (S)-1 are recognized in the chiral spaces formed between the layers of (R,R)-2. Molecular mechanics calculations showed that the chiral spaces formed in the crystals (S)-1:(R,R)-2 and (R)-1:(R,R)-2 are more suitable to accommodate (S)-1 and (R)-1 than (R)-1 and (S)-1, respectively. The present study has strongly suggested that DCR is a common phenomenon.

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