Answer to Question #117441 in General Chemistry for sara

Question

Escitalopram is a single enantiomer formulation of the SSRI antidepressant citalopram.
In the manufacturing route, racemic intermediate (±)-8 is treated with (+)-di(p-toluoyl) tartaric acid 9. The product is recrystallised and treated with sodium hydroxide to give enantio- enriched intermediate (S)-8. Explain the chemistry involved.

Answer 1

1) An (S)-enriched citalopram tartrate compound, wherein at least 70% of the citalopram moieties are the (S)-enantiomer of citalopram.

2) A process, which comprises treating a diastereomerically impure citalopram tartrate compound with formaldehyde to form an (S)-enriched citalopram tartrate compound.

3) Process, which comprises: resolving a citalopram tartrate compound in the presence of aqueous formaldehyde in one or more steps to form an (S)-enriched citalopram tartrate compound having at least 90% (S)-citalopram purity;

treating said (S)-enriched citalopram tartrate compound with base to form substantially (S)-citalopram; and optionally

reacting said substantially (S)-citalopram with oxalic acid to form (S)-citalopram oxalate.