1. Anjaneyulu, A.S.R.; Sagar, K.S.; Venugopal, M.J.R.V.; Tetrahedron, 1995, 51, 10997–11110 and references cited therein.
2. Anjaneyulu, A.S.R.; Krishna Murthy, M.V.R.; Rao, G.V.; Tetrahedron, 1997, 1997, 53, 9301–12 and the references cited therein.
3. Havellockate (1), C21H26O8, m.p. 212–13°C, [α]D25 + 23.70 (c, 0.43, C5H5N), 1H NMR (400 MHz, d5-pyridine) δ : 1.53 (3H, s, 19-Me), 1.73 (1H, dd, J = 13.3, 6.5, 9-Ha); 2.02 (3H, s, 17-Me); 2.08 (1H, d, J = 8.2, 7-H); 2.20 (1H, d, J = 13.3, 9-Hb); 2.90 (1H, d, J = 16.3, 4-Ha); 3.02 (1H, dd, J = 13.8, 2-Ha); 3.16 (1H, dd, J = 13.4, 2-Hb); 3.36 (1H, dd, J = 19.5, 6.5, 4-Hb); 3.46 (1H, d, J = 3, 12-H); 3.48 (1H, m, 11-H); 3.50 (3H, s, -OMe); 4.15 (1H, dd, J = 8.3, 1-H); 4.70 (1H,, d, J = 6, 5-H); 4.72 (1H, brs, -OH); 4.86 (1H, brs, 16-Ha); 5.02 (1H, m, 10-H); 5.27 (1H, brs, 16-Hb); 6.34 (1H, d, J = 3, 13-H); 7.48 (1H, br, -OH); 13C NMR (22.5 MHz, d5-pyridine) δ : 20.7 (q, C-17); 28.1 (q, C-19); 38.2 (t); 39.1 (t); 40.3 (d); 40.4 (d); 44.8 (d); 49.0 (d); 5.10 (t, C-9); 51.3 (q. -OMe); 76.0 (d); 80.2 (d); 81.8 (s, C-8); 91.7 (s, C-6); 112.9 (t, C-16); 123.1 (d, C-13); 138.3 (s, C-14); 147.9 (s, C-15); 173.1 (s, C-3); 175.8 (s, C-18); 176.4 (s, C-20).
4. Venkateswarlu, Y.; Farooq Biabani, M.A.; Venkata Rami Reddy, M.; Prabhakar Rao, T.; Kunwar, A.C.; Faulkner, D.J.; Tetrahedron Lett., 1994, 2249–2252.