if A grants a parcel to B but doesn't gain good title until after the grant, when A does acquire good title it automatically passes to B (3 Miller & Starr, Cal. Real Est. s8:74 (4th ed.).
I've seen this in 19th century transactions. A grants aliquot to B, B to C, C to D, A gets the U.S. Patent 10 years after the original grant, D automatically receives the title.
According to Miller & Starr there could be an interesting wrinkle in a Sr.-Jr. Rights overlap. Say A owns 100' wide subdivision lot. A grants west 50' to B. Then A grants C the east 50'. Survey reveals the lot is only 95' wide. B's half is 50' wide because he is senior (or has paramount title). C' half is 45' wide because he is junior (inferior title). Now here's the "but"...if A reacquires the west 50' then C would succeed to the east 5' of the west 50' (the overlap area) under the After-acquired title doctrine. They don't cite a case for this so maybe it's theoretical. They cite other sections in their treatise.
Note: this only operates for Grant Deeds, the after-acquired title rule does not apply to quitclaim deeds.
Thanks for the refresher. I recall a 1900 era deed where the grantor clearly did not yet have title to all of what was described, somehow referring to "lands that the grantor will come to own", or something like that. At the time I thought "what is going on here?" Now when I recall the project I think "now what was the name of that doctrine again...?"