Synthesis of dimer and oligomers from (R)-methyl hydnocarpate

We report synthesis and characterization of dimer and oligomer acids from chaulmoogra oil. (R)-Methyl hydnocarpate (methyl ester of the major fatty acid component of chaulmoogra oil) was brominated to give threo-2,3-dibromocyclopentane-1-methyl undecanoate. Formation of two diastereoisomers, viz., threo-2(R),3(R)-dibromocyclopentane-1(R)-methyl undecanoate and threo-2(S),3(S)-dibromocyclopentane-(R)-1-methyl undecanoate, was observed. Dehydrobromination of bromo derivatives using alcoholic KOH gave a cyclopentadiene derivative as intermediate, which underwent Diels-Alder reaction to give dimer and oligomer fatty acids. The products were characterized by ultraviolet, direct exposure probe-mass spectroscopy, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR spectroscopic techniques.