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20.5.10.1.2.5.2 Method 2: Diastereoselective Organocuprate Michael Addition to Chiral Piperazine-2,5-dione Acceptors

DOI: 10.1055/sos-SD-020-01043

Garbaccio, R. M.; Wolkenberg, S. E.Science of Synthesis, (2007201165.

Michael addition of organocuprates to the chiral piperazine-2,5-dione acceptor 105 provides a range of protected α-amino acid esters 106 and acids in excellent yield and stereoselectivity (Scheme 30).[‌148‌] The excellent cis diastereoselectivity observed arises from a chiral relay system from the isopropyl group through the adjacent 4-methoxybenzyl group to give high facial selectivity in the final protonation event. Deprotection requires three high-yielding steps and a fractional distillation to remove the valine template.

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