Conversions of seven-membered terpene lactones towards low-molecular bioregulators

Abstract

The review describes the low-temperature reduction of (-)-mentholactone with diisobutylaluminum hydride in methylene chloride studied by the authors. It was found that, depending on the reaction conditions, it proceeds with the formation of three products: 7 S -isopropyl-4 R -methyloxepan-2 S -ol [(-)-mentholactol], 8-hydroxy-2,6 R -dimethyloctan-3-one or 2 S -isobutoxy-7 S -isopropyl-4 R -methyloxepane, for each of which the probable routes are given and the conditions for selective formation are selected. A new reaction in the chemistry of organoaluminum compounds has been discovered - the formation of isobutyl acetals of 2-oxepanols during low-temperature (-70°C) reduction of 7-membered lactones with two-fold or more molar amounts of diisobutylaluminum hydride in methylene chloride. On the basis of (-)-mentholactol, its aluminate, and 8-hydroxy-2,6R-dimethyloctan-3-one, a number of low molecular weight bioregulators, including optically active pheromones of insect pests in agriculture and forestry, have been synthesized.