(require 'ox-latex)
(add-to-list 'org-latex-classes
             '("memoir"
               "\\documentclass{memoir}
  [NO-DEFAULT-PACKAGES]"
               ("\\chapter{%s}" . "\\chapter*{%s}")
               ("\\section{%s}" . "\\section*{%s}")
               ("\\subsection{%s}" . "\\subsection*{%s}")
               ("\\subsubsection{%s}" . "\\subsubsection*{%s}")))