An investor group led by Taggart/Fasola Group, a New Jersey-based professional management firm, has agreed to buy the 259-strong group for a price reliably estimated at pounds 30m.
This compares with a pounds 50m valuation on Isosceles' balance sheet, a figure itself reduced from pounds 195m in the 1992 accounts.
The chain was bought for pounds 280m when Gateway, then known as Dee Corporation, went on an expansion drive under its former chief executive, Alec Monk.
The sale comes as Isosceles, which bought Gateway in a highly leveraged deal three years ago, is trying to restructure its borrowings for the third time.
The group brought in a new chief executive, David Simons, late last year and since then has seen a string of departures, including Bob Nellist, the finance director, and Bryan Taker, the personnel director, as the group tries to come to grips with its financial problems.
Isosceles' 37 banks have agreed to a standstill until the end of May while the group and its advisers, Hill Samuel, come up with restructuring proposals. Close watchers estimate that there should be something on the table by the middle of next month.
Isosceles last restructured its debt in the middle of last year.Reuse content