NEW YORK - Syncora Guarantee Inc. filed a brief supporting its proof of claim in the Chapter 11 bankruptcy of Residential Capital LLC (ResCap) on Sept. 3, arguing that it insured more than $800 million in residential mortgage-backed securities (RMBS) under an agreement that GMAC Mortgage LLC (GMACM) - a division of ResCap - would comply with its obligations pursuant to a covenant between Syncora and GMACM (In Re: Residential Capital LLC, No. 12-12020, Chapter 11, S.D. N.Y. Bkcy.).