Nat. Chem. Biol. 13, 111–118 (2017); published online 21 November 2016; corrected after print 17 March 2017

In the version of this article initially published, some of the chemical compounds were incorrectly numbered as stereoisomers instead of racemates and some of the stereoisomers were marked with incorrect stereocenter configurations. In numerous instances throughout the main text and Online Methods, compounds 1–13 were incorrectly called 1R–13R (6 instances of 13R are correct and were left unchanged). In the legend for Figure 5: 1S, 4S, 11S, 12S, 13S were incorrectly called 1R, 4R, 11R, 12R, 13R, respectively; in the left column of p.115: 1S, 4S, 11S were incorrectly called 1R, 4R, 11R, respectively; and in the left column of p.116: 13S was incorrectly called 13R. The errors have been corrected in the HTML and PDF versions of the article.