Asymmetric Diels-Alder reactions: EPC-synthesis of a stable sarkomycin precursor (cyclosarkomycin)

Abstract The first synthesis of enantiomerically pure cyclosarkomycin, a stable, crystalline precursor of the antitumor agent sarkomycin is reported. Key steps are an asymmetric Diels-Alder reaction of the (E)-3-bromoacrylate of (R)-pantolactone and introduction of oxygen functionality via elimination/β-addition. The synthesis of cyclosarkomycin was accomplished in 9 steps [from (E)-3-bromoacrylic acid] in 17 % overall yield.