2D 13C-13C ssNMR spectra using 25 ms DARR mixing, providing 1–2 bond transfers. Measurements on samples p1–p3 are shown in panels (a)–(c), with (a) obtained at 800MHz 1H frequency and 16 kHz MAS, and (b, c) at 600 MHz 1H frequency and 10 and 13 kHz MAS, respectively. Spinning side bands are marked with asterisks. For each spectrum aliphatic-to-carbonyl (left) as well as the intra-aliphatic (right) spectral regions are shown.