Standard & Poor’s downgraded commercial mortgage-backed notes sold by a fund of Becton Property Group as the Australian developer seeks to sell assets to repay the debt. The top class of notes was downgraded five rungs to single-A from triple-A, the ratings firm said today in an e-mailed statement. S&P said it may cut the grades further if it sees an increasing prospect that bondholders won’t be repaid before the legal final maturity of the notes in 2012.