Tosefta על דמאי 6:11

How [else] is this done? We do not take terumah from produce from the Land [of Israel] on behalf of produce from outside the Land [of Israel], we do not take terumah from produce from the Land of Israel on behalf of produce from Syria (see Dem. 6:11), and not from produce from Syria on behalf of produce from the Land of Israel. A Jew that bought a field in Syria, behold, he is like someone who buys [a field] in the outskirts of Jerusalem (see Challah 4:11, "בְּפַרְוָר" = outskirts, not "בפרוזדור" = vestibule, see Lieberman here), and [therefore he must] take terumah and tithes on it.