* Grupo Rayet owns 42 percent of Quabit
* Has 593 million euros liabilities - Quabit spokeswoman
* Quabit says Rayet's woes do not affect its own viability
* Quabit shares down 8.7 percent (Adds detail, background)
By Tomás Cobos
MADRID, Nov 9 Grupo Rayet, a leading shareholder in the stock exchange listed property group which came to symbolise Spain's real estate boom and bust, is to file for bankruptcy after failing to renegotiate its debt.
Grupo Rayet, which owns 42 percent of listed real estate investor Quabit, said in a statement on Friday it would file for bankruptcy protection within the next few days after one creditor held out in talks on restructuring.
Rayet had 593 million euros ($755 million) of liabilities, 302 million of which is financial debt, a spokeswoman for Quabit said.
"This is not going to affect Quabit's business other than possible movements on the stock market," she said. "This is precisely about safeguarding the interests of the other companies Rayet has holdings in."
By 1245 GMT Quabit shares were down 8.7 percent at 0.042 euros, one of the largest declines in Spain on Friday.
Then called Astroc, Quabit's stock price jumped more than 10 times in less than a year after it was launched on the Madrid stock exchange in May 2006.
But an auditor's report in 2007 saying owner Enrique Banuelos had bought property from his own company equivalent to 65 percent of annual turnover, which had since lost around 85 percent of its value, sent the price plummeting and resulted in Banuelo's exit from the company.
Banuelos also lost his place on the Forbes 100 list of wealthy people when Spain's decade-long boom fuelled by cheap credit turned to bust.
House prices have fallen by as much as 40 percent from their 2007 peaks, while Spanish banks have had to take huge write-downs on property assets. More than half a million new homes in Spain lie empty.
Two Spanish investment firms that own 31 percent of French property company Gecina filed one of the biggest bankruptcy actions in Spanish history after a bank refused to refinance a 1.6 billion euro loan last month. ($1 = 0.7857 euros) (Additional reporting and writing by Tracy Rucinski and Clare Kane; editing by Patrick Graham)