The invention provides (1) processes for making substantially-pure (−) huperzine A and substantially-pure (−) huperzine A derivatives； (2) compositions useful in making substantially-pure (−) huperzine A and substantially-pure (−) huperzine A derivatives； and (3) methods of treating or preventing neurological disorders using substantially-pure (−) huperzine A and substantially-pure (−) huperzine A derivatives.
