α,β-Epoxy\nKetone Rearrangements for the\nPractical Synthesis of Cephalotaxine and the Stereodivergent Synthesis\nof Azaspiro Allylic Alcohols

We\nreport herein that three facile rearrangements of\nepoxy ketones\ncan be employed for the efficient and practical synthesis of cephalotaxine,\nthe parent member of the family of <i>Cephalotaxus</i> alkaloids.\nThe Meinwald rearrangement of epoxy ketone (90%) was used for the\npreparation of the dense functional groups in the cyclopentane ring\nof cephalotaxine. A novel acid-catalyzed umpolung S<sub>N</sub>2′\nrearrangement and the Wharton transposition reaction of epoxy ketones\nwere also developed to synthesize the Mori intermediate via the key\nazaspiro allylic alcohols in a stereodivergent manner.