"alla"

This is interesting, from "The Jewish New Testament Commentary" on Romans 10:6-8, page 399:

"Perhaps the most cogent reason for rejecting sense (2) for 'de' is that Greek has a different word, "alla," which is a strong adversative, which Sha'ul could have used had he meant to present an alternative way of being considered righteous by God. Had he written "alla," it could only have been translated, "but, on the contrary, in contrast."

Hmmmm, coincidence?

Adversative: 1. expressing contrariety, opposition, or antithesis.