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■ Asymmetric Synthesis of Tertiary 2-Substituted 5-Oxotetrahydrofuran-2-carboxylic Acids

Anne Paju, Karolin Oja, Katharina Matkevitš, Priit Lumi, Ivar Järving, Tõnis Pehk, and Margus Lopp*

*Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, Tallinn, Estonia

Abstract

3-Substituted 1,2-cyclopentanediones 1 were transformed to 2-substituted 5-oxotetrahydrofuran-2-carboxylic acids 2 using a catalytic process with 0.2-0.3 equivalent of Ti(OiPr)4/tartaric ester/tBuOOH complex in up to 72% isolated yield and up to 94% ee. Different functional groups in the 3-alkyl substituent of 1 like, hydroxy, ether, Boc-amino and ester groups are tolerated. Boc-aminomethyl substituents lead to β-amino acid analogues and Boc-aminoethyl substituent to γ-amino acid analogues as well as spiro-lactone-lactams. A direct, two-step procedure for homocitric acid synthesis is described.