Complex sentence: ABG Gas Supply was created and secured loans from Citigroup, Credit Suisse First Boston, and Deutsche Bank to buy natural gas at market prices to then sell the gas at a discount to Dynegy, which resold it at market prices for $300 million in profit.
Split into simpler sentences: ABG Gas Supply was created and secured loans from Citigroup, Credit Suisse First Boston, and Deutsche Bank to buy natural gas at market prices. ABG then sold this gas at a discount to Dynegy, which resold it at market prices for $300 million in profit.