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. Author manuscript; available in PMC: 2016 Jul 1.
Published in final edited form as: Bioorg Med Chem. 2015 Apr 9;23(13):3603–3617. doi: 10.1016/j.bmc.2015.04.006

Figure 2.

Figure 2

Partial 1H NMR spectra show slight differences in the chemical shifts of the 31 methyl proton doublets of compound 3 (B) and compound 4 (C). In compound 2 (A) both doublets are present, as expected for the mixture containing both forms. In both (B) and (C), the presence of only one set of peaks suggests that 3 and 4 are isomerically pure.