Acylation of Meldrum's acid (I) with 3-tryphenylmethylsulfanyl)propionic acid (II) by means of DCC produces the intermediate adduct (III), which is subsequently reduced to the tritylsulfanyl derivative (IV) by using NaBH4/AcOH. Alkylation of (IV) with methyl 3-bromopropionate (V) in the presence of NaOMe provides the 5,5-disubstituted dioxanedione (VI). Basic hydrolysis of (VI) gives rise to the tricarboxylic acid (VII), which is further decarboxylated to (VIII) in hot DMSO. Finally the S-trityl protecting gropu is removed by treatment with trifluoroacetic acid and triisopropylsilane.