Processes are provided for preparing compounds with a fused ring structure of formula (XIV). Such products include ecteinascidins and have a spiroamine-1,4-bridge. The process involving forming a 1,4 bridge using a 1-labile, 10-hydroxy, 18-protected hydroxyl, di-6,8-en-5-one fused ring compound. After formation of the 1,4 brige, C-18 protection is removed before spiroamine introduction.