SYNTHESIS OF OCTALACTIN LACTONE AND SIDE-CHAIN

Two key intermediates of (+)-octalactin A, a potent new cytotoxic natu ral product, have been synthesized in a direct, and efficient manner. Lactone 1 was made using a substrate controlled lactonization reaction using the carbodiimide EDCI and two crotylborane additions were used to access the precursor hydroxyacid. The importance of proper substitu tion in the hydroxyacid tether is noted for successful medium-ring lac tonization. Synthesis of the side chain vinyl iodide 2 employed an asy mmetric allenylboronate addition. Copyright (C) 1996 Elsevier Science Ltd