Leading Question

Provide an explanation for the observed diastereoselectivity:

The final product results in a 67% yield. The addition of the azide is regioselective due to the resonance stabilization from the nearby oxygen atom. An inseparable 3.5:1 diastereomeric mixture is produced, with the equatorial position of the azide favored. This preference is due to the less 1,3-diaxial interactions with the large carbobenzyloxy group bonded to the ring. Because the area for the nitrate addition is sp2, it is planar. Because of this, the position of nitrate group is not stereospecific. Since the nitrate itself is also planar, its 1,3-diaxial interactions with the axial hydrogen atoms are relatively neglible.