LEADER <LDCO> BUYS PETROSURANCE STAKE Leader Development Corp said it has purchased 300,000 shares of convertible preferred stock in <Petrosurance Inc> for 1,500,000 dlrs in cash and real estate. Petrosurance specializes in property and casualty insurance for the oil industry. Leader said the stock is convertible into a Petrosurance common. Leader said it already owns 12.5 pct of Petrorusrance and conversion would give it about 45.0 pct. The company said Petrosurance will use the sale proceeds to support growth and improve the structure of its reinsurance treaties to retain a larger part of premiums written.