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Please login to access the full content or check if you have access via20.5.10.1.2.5.2 Method 2: Diastereoselective Organocuprate Michael Addition to Chiral Piperazine-2,5-dione Acceptors
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Garbaccio, R. M.; Wolkenberg, S. E., Science of Synthesis, (2007) 20, 1165.
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.
Meeeee 88 Meeeeeeeeeeeeeeeee Meeeeeeeeeeee Meeeeee Meeeeeee ee Meeeee Meeeeeeeee-8,8-eeeee Meeeeeeee[888]
M8 | M/MM | ee (%) | Meeee (%) ee 888 | Mee |
---|---|---|---|---|
Me | Me | >88 | 88 | [888] |
e-Me | MeMe | >88 | 88 | [888] |
Me | Me | >88 | 88 | [888] |
Me | Me | >88 | 88 | [888] |
Me | MeMe | >88 | 88 | [888] |
eMe | MeMe | >88 | 88 | [888] |
Meeeeeeeeeee Meeeeeeee
Meeeeeeee α-Meeee Meee Meeeee 888; Meeeeee Meeeeeeee:[888]
MMMMMMM: Meeeeee eeeee eee ee eeeeeeee eeeeeee eee eeee eee eee eeeeeeeee eeeee.
Me e eeeee-eeeee Meeeeee eeee eeeeeee eeee eeeee MeMM (8.88 eeee) eee eeeee MMM (88 eM) ee −88°M eeeee e M8 eeeeeeeeee eee eeeee eee eeeeeeeeeeee ee Meeeeeee eeeeeee (8.88 eeee). Mee eeeeeeeeee eee eeeeeee ee eeee ee −88°M eee 8 eee eeeee ee eeeeeee ee eee eeeeeee eeee. Mee eeeeeee eee eeee eeeeeee ee eeeeee eeee ee −88°M, ee eeeee eeee ee eee eeeeee eeeeeeeeeee. Meee eeeeeee eee eeee eeeeeeee ee −88°M, MM8•MMe8 (8.88 eeee) eee eeeee, eee eee eeeeeeee eee eeeeeee eee 88 eee ee −88°M. Meee, eeeeeeeeeeeeeee 888 (8.88 eeee) eee eeeee eee eee eeeeeeee eee eeeeeee eee 8 e ee −88°M, eee eeee eeeeeee ee eeee ee ee eeee 8–8 e. Mee eeeeeee eee eeeeeeee eeee eee. ee MM8Me (88 eM),eee eeeeeeeee eeee Me8M (8 eM) eee eeee MeMMe (8 × 8 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee eeee M8M (8 eM) eee eeeee (MeMM8), eee eee eeeeeeee eeee eeeeeee eeeee eeeeeee eeeeeeee. Meeeeeee eeee eeeeeeee eeeeee ee eeeeeeeeeeeeeeeee eeee eee eeeee eee ee eee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeee); eeeee: 88–88% (>88% ee).
References
[148] | Meee, M. M.; Meeeee, M. M.; Meeeee, M.; M'Meee, M. M., M. Meee. Mee., Meeeee Meeee. 8, (8888), 8888. |