A methodology for the synthesis of cyclopentanoid natural products containing two vicinal quaternary carbon atoms

Abstract

A six-step general methodology has been developed tor the synthesis of cyclopentanones containing two victnal quaternary carbon atoms starting from beta, gama, y-trisubstituted allyl alcohols. The three key reactions present in the sequence are: (i) the one-step Johnson's ortho ester Claisen rearrangement of allyl alcohols: (1,) intramolecular cyclopropanation of y, 8-unsaturated alpha-diazo ketones; and (iii) the regiospecific ring opening of the cyclopropyl ketones employing lithium in liquid ammoma reduction conditions. 'The synthetic utility at this melhodology was exemplified by the total synthesis of the sesquiterpenoids. cyclolaurene, beta-cuparenone. albene and thapsanes.