With two of Donohue Brown Mathewson & Smyth LLC’s named partners in semiretirement, the firm is going through a leadership transition, said Mark M. Burden, who stepped down earlier this year as managing partner.Karen Kies DeGrand was elected to serve as the firm’s managing partner. Burden served in the role since 2016. The firm announced DeGrand’s promotion last month.DeGrand and Burden were among the …