“…1 H NMR (400 MHz, CD 3 CN): δ 6.32 (bs, 1H exchanges) 4.55–4.44 (m, 1H), 4.29–4.24 (m, 1H), 3.76 (dd, J = 13.6, 8.4 Hz, 1H), 2.56 (s, 3H), 2.36 (s, 3H), 2.37–2.35 (m, 1H), 2.16 (dd, J = 13.3, 10.1 Hz, 1H), 1.90 (s, 3H), 1.69 (s, 3H), 1.58 (s, 3H); 13 C{ 1 H} NMR (101 MHz, DMSO- d 6 ): δ 187.7, 169.7, 71.2, 59.8, 46.4, 44.5, 27.9, 26.8, 25.4, 25.0, 22.4. Note: the spectral data is consistent with that reported for the perchlorate salt that can be found in ref .…”