anaphoric pronouns with indexical antecedents

This probably has a simple and not very interesting explanation having to do with syntactic constraints or morphological constraints or something. But why is it that the starred sentences below go wrong, given that they are obtained from the relevant non-stars by substitution of co-extensive expressions (i.e. `I' for `Brian')? The source of the problem here is obviously not intensionality!

(1) Brian left his wallet on the table.
(1*) I left his wallet on the table.

(2) Brian is such that John believes that he is a spy.
(2*) I am such that John believes that he is a spy.

(3) Brian went to the store and he bought tofu.
(3*) I went to the store and he bought tofu.

Can you think of an example where the referent of `I' can be picked up by an anaphoric pronoun? Is `I' itself sometimes an anaphoric pronoun? How does this relate to the following Heim example?

(4) Only I got a question I understood.