I also had an ImportError on _struct module during 'make install' when building 2.7.3 from source configured with --enable-shared. My solution, which *seems* to have worked, is simple:

   $ make -i install
   $ make install

My guess is that the part of the 'make install' that copies _struct.so into the correct place occurs AFTER a part of the 'make install' that tries to use it. If you tell make to ignore errors and carry on (-i), it then completes the installation, copies _struct.so (and everything else) into their correct places, and you can then do another make install without any errors!

I hope this helps someone track down a sensible fix, and in the mean-time provides a work-around for the rest of us.
(p.s. remember your PYTHONHOME and PYTHON_PATH should be clear before making)