This decision applies the Birnbaum buyer/seller rule to affirm dismissal of claims of shareholders in an acquiring company based on pre-merger misrepresentations made by the acquired company’s executives about the acquired corporation. In a case of alleged misstatements made in advance of an anticipated merger, purchasers of a security of an acquiring company do not have standing under § 10(b) to sue the target company for alleged misstatements that the target company made about itself prior to the merger between the two companies