I wondered about that. A veritable retail "research chemical!"Ah, that's right. The company changed a molecule so they could market it again in the US (zopiclone didn't do well on this side of the pond). That's how my shrink put it. Marketing - molecule - $$. Still leaves a horrible taste in our mouth - both do.
Sonata (I think that's a brand name) is another one, very short acting. Expensive.
Haven't yet tried it but I've often read about the annoying Zopiclone aftertaste. Hadn't heard one way or the other that it was also present with Eszopiclone (makes sense that it is present there as well).