A recent evaluation of the biol. activity of the tubulysin U and V diastereomers, that was in the Exptl. Section and Supporting Information of the recent Communication, suggest that the wrong diastereomers were selected for data presentation. Assignment of the tubuvaline (Tuv) spectra shown in the Supporting Information section should be inverted. Synthesis of the first building block, tubuphenylalanine (Tup), shown in Scheme 2 on page 7237, and in line with the procedure by Vicario et al. (2001), does not give the diastereomer shown but rather its C2 epimer as the major product (see revised Scheme 2, part A). The revised Scheme 2 shows the synthesis of the Me ester of epi-tubuphenylalanine (epi-Tup) as the major product by the pseudoephedrine route. The wrong C2 diastereomers epi-11 to epi-16 were produced as the major components, with only some of the correct diastereomers (compounds 11-16) formed. Synthesis of compounds 15 and 16 through a different pathway, using Enders' SAMP ((S)-(-)-1-amino-2-methoxymethylpyrrolidine) [Enders et al. (2000)] as auxiliary gave the correct diastereomer of the common intermediate 15 in 4 steps. Careful repetitions of the synthesis of Tup using the original unmodified procedure of Vicario et al. and our variations always led to the production of the wrong C2 diastereomers. Syntheses by the groups of Ellman [Peltier et al. (2006)] and Zanda [Sani et al. (2007)] have been reported, and a comparison of the sp. rotation values of compounds 14 and epi-14 with those reported by Zanda and coworkers confirmed the findings. It suggests that NMR spectroscopy is not ideal to determine the stereochem. of Tup. Tup and its C2 epimer can display almost identical behavior and spectra, depending considerable on the conditions used. The same is true for the Tup and Tuv diastereomers and the final products, most of which often behave very similarly with respect to NMR spectroscopy and chromatog. Spectra of both Tup epimers and a mixed spectrum are provided in the Supporting Information given. Exptl. data for the correct diastereomers are provided in the revised Supporting Information available online. The previously reported diastereomers have been updated with the corrected names, stereochem. descriptors, and formulas. In Table 1, column 1, G should read H.