The 19-year-old was thought to be a target for the Red Devils after Santos president Modesto Roma confirmed that the 20-time English champions had been in negotiations over a deal for the rising star.
Barbosa has scored 56 times in 152 appearances for Santos and has netted twice in four appearances for the Brazilian national team in his fledgling career so far.
Jose Mourinho has been one of the Premier League’s busiest managers this summer having signed four new players to bolster his Red Devils squad ahead of their disappointing fifth-placed finish under Louis van Gaal last term.
The United manager started his summer spending spree with the £30m acquisition of Villarreal defender Eric Bailly in June before Zlatan Ibrahimovic completed a free transfer from Ligue 1 champions Paris Saint-Germain.
Henrikh Mkhitaryan sealed a £30m switch to United from Borussia Dortmund last month before Mourinho finally secured a £92m deal for France and Juventus midfielder Paul Pogba.
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