DEPTQ spectrum of a 325 μg (9.25 μmol) sample of retrorsine in 120 μl of DMSO-d6. Recorded on a Bruker Avance AV 900 spectrometer equipped with a 5 mm TCI triple resonance inverse cryoprobe using DMSO-matched 3 mm Shigemi microcell assembly, with following parameters: deptqgpsp pulse program, SW = 239.50 ppm (54 200 Hz), TD = 64 K, LB = 3 Hz, SI = 256 K, D1 = 1.5 s, NS = 4 k, DS = 8, EXPT = 2 h 28′. SNR measured for quaternary signal at 175 ppm = 31. For protonated carbons SNR is between 100 and 140.