Despite the increasing importance and usefulness of phase transfer catalysis (PTC) in synthetic organic reactions, 1 catalytic asymmetric synthesis utilizing chiral phase-transfer catalysts remains poorly studied. [2][3][4] Yet, since the pioneering work of O 'Donnell et al. in 1989, asymmetric synthesis of R-amino acids by phase-transfer enantioselective alkylation of a prochiral protected glycine derivative 1 using a chiral catalyst has provided an attractive method for the preparation of both natural and unnatural amino acids. 5 Recently, the Corey 6 and Lygo groups 7 independently reported an impressive departure from the previous results in terms of enantioselectivity and general applicability. However, almost all of the elaborated chiral phase-transfer catalysts reported so far have been restricted to cinchona alkaloid derivatives, which unfortunately constitutes a major difficulty in rationally designing and fine-tuning catalysts to attain sufficient reactivity and selectivity for various chemical transformations under phase-transfer catalyzed conditions. 3,4 In this paper, we wish to describe a new, rational approach to this subject, i.e., the molecular design of a C 2 -symmetric chiral quaternary ammonium salt and its successful application to the highly efficient, catalytic enantioselective alkylation of tert-butyl glycinate-benzophenone Schiff base 1 under mild phase-transfer conditions.

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