Solid-phase synthetic method for (±)-α-amino acids via phase-transfer catalytic alkylation

Cinchona-based phase-transfer catalysts for asymmetric synthesis

Phase-transfer catalysis is one of the most useful methodologies for practical syntheses given its operational simplicity and mild reaction conditions that enable its application in industrial processes. Cinchona alkaloids have been a popular, natural source of practical organocatalysts due largely to their excellent commercial availability and low cost. Since the first Cinchona alkaloid-derived phase-transfer catalysts was disclosed in 1981, diverse generations of Cinchona-derived phase-transfer catalysts have been developed and successfully applied to various asymmetric syntheses. In this feature article, we describe the generation of Cinchona-derived chiral phase-transfer catalysts according to the development stages and our efforts toward the design of polymeric Cinchona phase-transfer catalysts, the effects of the electronic functional group incorporated in the catalysts, and their application in asymmetric organic reactions.

Soluble polymer-supported synthesis of 5-arylidene thiazolidinones and pyrimidinones using a novel traceless linker strategy

An efficient method for the soluble polymer-supported synthesis of 5-arylidene thiazolidinones and pyrimidinones using aniline as a traceless linker was described. Aldehyde substrates were attached to the polyethylene glycol (PEG)-bound aniline via an imine linkage, and after the subsequent PEG-promoted Suzuki coupling reaction for the diversification, Knoevenagel condensation was readily employed as the cleavage strategy.

Wang-aldehyde resin as a recyclable support for the synthesis of α,α-disubstituted amino acid derivatives

Merrifield resin was functionalised with hydroxybenzaldehyde under microwave irradiation. The resultant resin was used as a means for immobilisation and activation of alpha-amino acid esters for alkylation reactions. Alpha,alpha-disubstituted and cyclic amino acid esters were prepared in good yields.