Chapter 22, Problem 42P

Even though B contains three ester groups, a single Dieckmann product results when B is treated with ${\text{NaOCH}}_{\text{3}}$ in ${\text{CH}}_{\text{3}}\text{OH}$, followed by ${\text{H}}_{\text{3}}{\text{O}}^{+}$. Draw the structure and explain why it is the only product formed.