Under the whole heaven there has not been done …: This says the same as “Nowhere else on earth have such things happened…” (Good News Translation). Note that Good News Translation has perceptively inserted the word “else”; otherwise it would be an absurd statement, saying that what has happened has happened nowhere—including Jerusalem.

Has not been done … what he has done makes use of two forms of the same verb. Good News Translation uses “happened” as an effective equivalent, although it omits from the statement that it was God who did these things. “The Lord carried out the threats” picks up the idea, however.

“The threats” (Good News Translation) are not mentioned in the Greek text, but in accordance with what is written in the law of Moses surely refers to the threats of Bar 1.20 and 2.1. For the content of the threats, see Lev 26.14-39 and Deut 28.15-68. For the law of Moses, we may also say “the Law that Moses gave.”

It is possible to reorder the clauses in this verse in the following way:

• The Lord severely punished the city of Jerusalem, just as he threatened [or, warned] in the Law of Moses [or, the Law that Moses gave to Israel]. Nowhere else on earth have such things happened as happened there.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on The Shorter Books of the Deuterocanon. (UBS Helps for Translators). New York: UBS, 2006. For this and other handbooks for translators see here.