This is not supported.
RFCOMM is a set of simple transport protocols built on top of L2CAP and sometimes referred to as serial port emulation. The Bluetooth serial port profile, or SPP is based on this protocol.
SPP is RFCOMM based profile for Bluetooth Classic BR/EDR connections only. SPP over BLE (i.e. 20732/20736/20737) is not theoretically possible.
It is pretty simple to do “SPP-like” connection and pass data between 2 devices, but the mechanism will not be interoperable with other BLE devices. Of course, interoperability should not be a problem if your application is on both ends of the connection (ex. an application on the iPhone and a device).
