  It is argued that N=6 supergravity on $AdS_5$, with gauge group $SU(3)\times
U(1)$ corresponds, at the classical level, to a subsector of the ``chiral''
primary operators of N=4 Yang-Mills theories. This projection involves a
``duality transformation'' of N=4 Yang-Mills theory and therefore can be valid
if the coupling is at a self-dual point, or for those amplitudes that do not
depend on the coupling constant.
