Knoevenagel condensation between N-Boc-4-piperidinone (I) and ethyl cyanoacetate (II) produced the piperidinylidene cyanoacetate (III), which was further converted to the thienopyridine derivative (IV) upon treatment with sulfur and morpholine. Acylation of amine (IV) with ethyl oxalyl chloride (V) furnished the oxalamide (VI). Subsequent hydrolysis of the ester groups of (VI) under basic conditions led to diacid (VII). The title compound was finally obtained by trifluoroacetic acid-promoted Boc group cleavage.