1. L.M. Jackman, in L. Zechmeister ed., Progress in Chemistry of Natural Products 23, 315.
2. See the discussion in W.B. Whalley, in Heterocyclic Compounds, R.C. Elderfield ed. 7, 138.
3. Claisen rearrangements in the xanthone series and synthesis of dihydroisojacareubin
4. G. Cardillo, L. Merlini, R. Mondelli, Tetrahedron, in press.