how do i reduce a fruit puree to a syrup-y consistency without sugar

You cannot reduce it without cooking it down. You can thicken it by using potato or corn starch, but that won't reduce it.

thanks, & you're absolutely right. i should have mentioned that i'm trying to make it paleo, so no starch thickeners allowed. any ideas how long before it reduces?

If you have time cook it down that is best. If not cornstarch will work in a pinch.