Adams, 23, is set to join for a fee of around £20million, with the Whites moving to wrap up a deal for the American after selling Kalvin Phillips to Manchester City for £42million.
Sinisterra, who is also 23, is arriving as a potential replacement for Raphinha, who is wanted by Barcelona and Chelsea.
The Colombia international is set to cost around £20million too.
Adams - captain of the US national team - is well known to Leeds boss and fellow countryman Jesse Marsch.
Marsch managed him during their time together at both New York Red Bulls and RB Leipzig.
While Adams is a central midfielder, he can also play at right-back, where has has featured for the US.
Sinisterra, meanwhile, has been at Feyenoord for the past four years and had his best season in 2021/22.
The exciting winger scored 23 goals and registered 14 assists in all competitions.
It is likely he will be a direct replacement for Raphinha.
Arsenal had previously seen two bids rejected for the 25-year-old, and despite Leeds accepting a £60m offer for their star from Chelsea, the player is understood to be holding out for a move to Barcelona.