Hydroxymercuration, cyclization, and reduction of appropriate hydroxy ketones or enones carrying a suitably located a, &unsaturated ester function is an efficient route to exogonic acid (2-(carboxymethyl)-7-methyl-1, 6-dioxaspiro [4.4] nonane), a resin constituent of the Brazilian tree Ipomoea operculata (Martin), and related [4.5] and [5.5] spiroketal systems. Procedures incorporating stereocontrol at C-2 and C-7 of exogonic acid are also reported ...
