Synthesis of 15-Deoxy-16β-Ethoxybruceantin and Synthetic Efforts toward Bruceantin

Article abstract of DOI:10.1021/jo00081a008

Utilization of asymmetric Michael addition leads to chiral phenanthrenone (+)-4 suitable for the synthesis of Bruceantin.The D-ring is assembled by means of an intramolecular alkylation of the bromoacetals 25 while only the axial diastereomer 25ax proceeds smoothly.The formation of the cyanohydrin introduces the C-13 carboxyl group and tandem intramolecular alkylation provides the furan E-ring.The C-11,12 cis-diol 39 is readily transformed to the trans-diol 42 via an unusual Swern-type oxidation/reduction sequence.The C-2,3 olefin proves to be an efficient progenitor for the A-ring diosphenol function which can be introduced at the late stage of this synthesis. 15-Deoxy-16β-ethoxybruceantin 3 is accordingly prepared.Attempts to elaborate common intermediates toward the synthesis of bruceantin are described.The presence of an oxygen function at C-15 drastically changes the relative reactivity of the C-2,3 and C-11,12 olefinic bonds.