Hi blindsoccer,
It is possible. I use an Apple Thunderbolt to Firewire 800 adapter, to which I connect some generic Firewire 800 to Firewire 400 adapter to which I connect the Firewire 400 cable from the Fireface 400. (As an alternative, I have also used a Firewire 400 (male) to firewire 800 (male) cable, which can connect to the Apple Thunderbolt to Firewire 800 adapter. No need for the generic Firewire 400 to 800 adapter then, but I prefer RME's longer Firewire 400 cable, so I still use the generic adapter.) Install the laters drivers and firmware from RME's download section. However, DigiCheck currently doesn't work with this OS, until they update it.