Stefano Pessina, the 73-year-old billionaire who built up Alliance Boots, is set to act as interim chief executive of Walgreen Boots Alliance after Walgreens' full takeover next February of Alliance Boots, parent company of Boots Opticians. Pessina is already executive chairman of Alliance Boots. Walgreens, whose shareholders will vote on the merger on Dec. 29, had previously intended to place the big, combined group under the leadership of its president and CEO, Greg Wasson, but he has announced that he plans to retire. Ornella Barra, Pessina's long-standing partner in charge of wholesale and brands at Alliance Boots, is still expected to become executive vice-president of the new group and as president and CEO of global wholesale and international retail. James Skinner, chairman of Walgreens, will assume some executive duties pending the recruitment of a permanent CEO for the new entire group.