"Unfortunately, I cannot come."
Translation:Jeg kan dessverre ikke komme.
"No split infinitives" is a 19th century prescriptivist "rule" that has no more real force than "you can't end a sentence with a preposition" (or "a preposition is something you can't end a sentence with"). I could certainly imagine some English lord saying "I can, unfortunately, not come" (same word ordering). It's just more natural in the default translation, that's all.