Manual install of pre-compiled version of dropbox works.
https://aur4.archlinux.org/packages/dropbox/
Use pkgfile for install directions,fetch dropbox.deskop and dropbox.png 
from git tree.  

i686: https://dl.dropboxusercontent.com/u/17/dropbox-lnx.x86-3.6.9.tar.gz
x86_64: 
https://dl.dropboxusercontent.com/u/17/dropbox-lnx.x86_64-3.6.9.tar.gz