21 Asymmetric Synthesis Involving Dynamic Enantioselective …
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Fig. 21.8 Asymmetric synthesis using Michael addition followed by dynamic crystallization
involving deracemization by deprotonation
reduced the induction period, and deracemization started after 4 days and gave 80%
ee of the solid after 7 days.
Kawasaki et al. reported a valuable synthetic example of an amino acid precursor
by the Strecker reaction followed by crystallization with racemization in the presence
of a base leading to α-aminonitrile 31 in up to 96% ee (Fig. 21.9) [60, 61].
Noorduin et al. also reported the Strecker reaction to Viedma ripening for the
absolute asymmetric synthesis of highly sterically hindered α-amino acids, and the
enantiomerically pure α-amino acids 32, tert-leucine, and α-(1-adamantyl)glycine
were obtained (Fig. 21.10) [62].
Fig. 21.9 Asymmetric Strecker synthesis followed by dynamic crystallization