Although it wasn't always official, for many years it has been an accepted part of Star Trek canon that Robert April was the first captain of the USS Enterprise (NCC-1701). April was first introduced in The Animated Series, and he has since become a Star Trek fact as far as the Prime timeline is concerned. He took command of the newly-constructed starship in 2245, taking it on its first 5-year mission, before being succeeded by Christopher Pike, James Kirk, and eventually Spock.
In the alternate Star Trek timeline stemming from Star Trek (2009), the Enterprise is constructed a decade later than in the Prime timeline — 2255 to be exact, and Christopher Pike is its first captain rather than April.
According to Robert April's Memory Alpha biography (linked above), he was born in 2195. Likely, he attended Starfleet Academy in the late 2210s or the early 2220s. In any case, he would have certainly been a Starfleet officer by the time of Nero's incursion, if not a captain of a vessel.
Is there any information, canonical or not, on April's career in the alternate timeline?
In terms of alternate timeline canon, we only have Star Trek: Countdown, Star Trek, and Star Trek Into Darkness to go on. Neither of the two films mentions April, and I do not own Countdown and have not read it fully. Does April receive mention in any original novels, novelizations, comic books, or other media, with regards to the alternate timeline?