A schematic of the solution is shown below. The information from the question is given in black. Deductions directly from this
information are given in red. Points that provide potential key information are shown by green arrows which leads to the
structures which are linked via the blue arrows to show the path required to work them all out. There are, of course, other
possible thought pathways. The keys here are (i) realising B is a cyclopentane system or (ii) using the structure of 5,6-dioxodecanedioic acid to get D. B can be used to get A from which the other structures are derived.