General NMR Spectroscopy

All NMR experiments were performed at 20 °C using an AVANCE II 700 MHz NMR spectrometer (Bruker) equipped with a TCI cryogenic probe with the exception of in-phase/anti-phase (IPAP) HSQC experiments, which were performed on an AVANCE 600 MHz NMR spectrometer (Bruker) equipped with a TXI cryogenic probe. NMR samples contained 5% deuterium oxide (Cambridge Isotope Laboratories) and were measured in 5 mm-diameter Shigemi tubes (Shigemi). Sodium 3-(trimethylsilyl)-1-propanesulfonate (Tokyo Chemical Industry) was used as an external standard of the ¹H chemical shift; ¹³C and ¹⁵N chemical shifts were calibrated indirectly.⁴⁰ All acquired NMR data (i.e., free induction decays) were processed using NMRPipe,⁴¹ and the resulting spectra were further analyzed using various software packages (see below).