Thiazoline-based substrate

The group of Park and Jew developed the efficient reaction systems for the preparation of optically active a-alkylserine and a-alkylcysteine derivatives (Scheme 6.15) [40], The group developed the oxazoline-based substrate for serines 52a and the thiazoline-based substrate 52b for cysteines, respectively. The oxazoline and thiazoline moieties fulfilled a dual function the activation of the a-proton and the protection of both the amino and the side chain hydroxy groups. The ortho-biphenyl derivatives 52a and 52b were specifically designed for the cinchona PTC 54, and solid cesium hydroxide monohydrate was chosen as an optimal base. The PTC 29 was also found to be as effective as the PTC 54 for the asymmetric alkylation of 52a. 

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