Synthesis of (+)‐1,3:2,5‐dianhydroviburnitol ((+)‐(1R,2R,3S,5R,6S)‐4,7‐dioxatricyclo[3.2.1.03,6]octan‐2‐ol)

Abstract

AbstractEpoxidation of (−)‐(1R,2R,4R)‐2‐endo‐cyano‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐exo‐yl acetate ((−)‐5) followed by saponification afforded (+)‐(1R,4R,5R,6R)‐5,6‐exo‐epoxy‐7‐oxabicyclo[2.2.1]heptan‐2‐one ((+)‐7). Reduction of (+)‐7 with diisobutylaluminium hydride (DIBAH) gave (+)‐1,3:2,5‐dianhydroviburnitol ( = (+)‐(1R,2R,3S,4R,6S)‐4,7‐dioxatricyclo[3.2.1.03,6]octan‐2‐ol; (+)‐3). Hydride reductions of (±)‐7 were less exo‐face selective than reductions of bicyclo[2.2.1]heptan‐2‐one and its derivatives with NaBH4, AlH3, and LiAlH4 probably because of smaller steric hindrance to endo‐face hydride attack when C(5) and C(6) of the bicyclo‐[2.2.1]heptan‐2‐one are part of an exo oxirane ring.