Microwave-Assisted Synthesis of Substituted Tetrahydropyrans Catalyzed by ZrCl₄ and Its Application in the Asymmetric Synthesis of exo- and endo-brevicomin

The ZrCl4-catalyzed deprotection of 1,3-dioxane/dioxalane and the simultaneous formation of 6-methoxy-substituted tetrahydropyrans proceeded under microwave irradiation in good yield. This synthetic methodology was used for the asymmetric synthesis of (+)-exo- and (+)-endo-brevicomin in 55% overall yield over 4 steps.