Business, lawsuits and friendship can make for a combustible mix. One well-known Center City, Pa., attorney and a Main Line-based drugstore chain heir, who until recently traveled in the same social circles, are finding that out the hard way.

Rosen v. Sylk, which has been assigned to Judge Albert W. Sheppard Jr. of Philadelphia’s Commerce Case Management Program, stems from a dispute over interests in a proposed steel plant in Estonia.