Is there any way to map the Synaptics gestures to specific keyboard shortcuts? In particular, I'm trying to map Dexpot's forward/backward between desktops to touchpad gestures.
If your driver supports it, you can enable Tap Zones.
When you have Tap Zones enabled, you can map the corners of your touchpad to certain actions that you can choose. Among them, there is the option to "Record and play a sequence of keystrokes". I think that is what you need.