I have a 3802 and the remote does not have a separate bass boost button on it. However you can adjust the bass (and treble) via the Parameter settings by using the remote.
Strangely, Denon doesn't list the center frequencies of the bass and treble controls. But 99% of the frequencies I have seen listed are 10 kHz for the treble and 100 Hz for the bass. I'd bet it's close to that for the Denons too.