Wachovia Corp. said it will buy Central Fidelity Banks Inc. of Richmond, Va., for $2.3 billion in stock, a move that would make it Virginia’s largest bank. . . . The New York Stock Exchange said it began quoting stock prices in sixteenths of a dollar Tuesday. . . . Encyclopaedia Britannica Inc. in Chicago has named Paul Hoffman, previously editor in chief of Walt Disney Co.'s Discover magazine, to the newly created position of publisher, as it establishes a new executive team for expanding its business. . . . Louis Dreyfus Natural Gas Corp. said it will buy American Exploration Co., another independent oil and gas producer, for $350 million in cash and stock to create a company valued at $1.1 billion. . . . Johnson & Johnson’s Janssen Pharmaceutica unit failed to win the backing of a Food and Drug Administration advisory panel for its new prostate cancer drug.