Synthesis of the Tetrasaccharide Glycone Part of Tetrocarcin A.

A de novo synthesis of the tetrasaccharide fragment of tetrocarcin A is described. The key feature of this approach is highlighted by the regio- and diastereoselective Pd-catalyzed hydroalkoxylation of ene-alkoxyallenes with an unprotected l-digitoxose glycoside. The subsequent reaction with digitoxal in combination with chemoselective hydrogenation generated the target molecule.