Shrodinger's Equation is analogous to Newton's Second Law in classical physics.
There is no derivation of Newton's Second Law. It is based completely off our observations and experiments showing, directly or indirectly, that F=ma. The same is true for the Shrodinger Equation. Once we observed that matter had wave properties, the Shrodinger Equation was devised to describe those properties. The equation is accepted because experiments have shown that it, (or more generally, it's relativistic counterpart) it makes very accurate predictions. This is how physics works. The ultimate proof is not mathematical, but natural. You can have an amazing derivation for a given equation, but if it doesn't agree with nature, it is not physics.