A convergent synthesis of the tetrasaccharide subunit in the proposed structure of durantanin I is reported. The signature step is represented by the unique assembly of apiofuranoside ring by the sequential PdRu metal catalysis. Per‐dihydroxylation at the late stage delivered the target compound in a highly efficient manner. In addition, a tetrasaccharide derivative possessing unnatural apiose unit was also synthesized with comparable efficiency to that for the natural form.