Two Seattle-area men pleaded guilty Friday to federal charges stemming from an illegal tax shelter that enabled wealthy clients — including philanthropist Robert Wood Johnson IV and Egyptian-born Hollywood mogul Haim Saban — to avoid paying taxes on $1.3 billion in capital gains.

The men ran an investment firm called Quellos Group LLC. Jeffrey Greenstein, 48, was its chief executive and Charles H. Wilk, 51, was its tax attorney.