- Asymmetric conjugate reductions with samarium diiodide: Asymmetric synthesis of (2S,3R)- And (2S,3S)-[2-2H,3-2H]-leucine-(S)- phenylalanine dipeptides and (2S,3R)-[2-2H,3-2H]- phenylalanine methyl ester
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The highly diastereoselective samarium diiodide and D2O-promoted conjugate reduction of homochiral (E)- and (Z)-benzylidene and isobutylidene diketopiperazines (E)-5,7 and (Z)-6,8 has been demonstrated. This methodology allows the asymmetric synthesis of methyl (2S,3R)-dideuteriophenylalanine 27 in ≥95% de and >98% ee, and (2S,3R)- or (2S,3S)-dideuterioleucine-(S)- phenylalanine dipeptides 37 and 38 in moderate de, 66% and 74% respectively. A mechanism is proposed to account for this process. The Royal Society of Chemistry 2005.
- Davies, Stephen G.,Rodriguez-Solla, Humberto,Tamayo, Juan A.,Cowley, Andrew R.,Concellon, Carmen,Garner, A. Christopher,Parkes, Alastair L.,Smith, Andrew D.
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p. 1435 - 1447
(2007/10/03)
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- 2-Halo-diketopiperazines as chiral glycine cation equivalents
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A range of (2S,5S)-5-isopropyl-2-halo-N,N′-bis-(p-methoxybenzyl)- piperazine-3,6-diones 8 (Cl), 11, 12 (F) and 13 (Br) have been prepared, either via electrophilic halogenation of the corresponding lithiated diketopiperazine, or via transhalogenation from
- Bull, Steven D.,Davies, Stephen G.,Garner, A. Christopher,Savory, Edward D.,Snow, Emma J.,Smith, Andrew D.
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p. 3989 - 4001
(2007/10/03)
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- Conjugate additions of organocuprates to a 3-methylene-6-isopropyldiketopiperazine acceptor for the asymmetric synthesis of homochiral α-amino acids
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Addition of a range of organocuprates to (S)-N,N′-bis(p-methoxybenzyl)-3-methylene-6-isopropylpiperazine-2, 5-dione 8 affords cis-3-isopropyl-6-alkyldiketopiperazines in excellent yield and >95% de. Subsequent deprotection and hydrolysis of these cis-3-isopropyl-6-alkyldiketopiperazines affords homochiral (S)-α-amino acids in excellent yield.
- Bull,Davies,Garner,O'Shea
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p. 3281 - 3287
(2007/10/03)
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- Stereoselective conjugate addition of organocuprates to a dehydroalanine derived diketopiperazine
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An asymmetric synthesis of homochiral α-amino acids has been developed which is based on the conjugate addition of organocuprates to the dehydroalanine equivalent (3S)-N,N′-bis(p-methoxybenzyl)-3-isopropyl-6-methylenepiperazine-2,5-dione 6.
- Bull, Steven D.,Davies, Stephen G.,O'Shea, Michael D.
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p. 3657 - 3658
(2007/10/03)
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- Deracemisation of α-amino acids - (R)- and (S)-phenylalanine from the same enantiomer of a homochiral auxiliary
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Chiral auxiliary (3S)-N,N'-bis-(p-methoxybenzyl)-3-isopropylpiperazine- 2,5-dione 1 was employed for the synthesis of both enantiomers of phenylalanine using a regioselective deprotonation/stereoselective reprotonation strategy. Modification of this approach enables the efficient deracemisation of (±)-phenylalanine.
- Bull, Steven D.,Davies, Stephen G.,Epstein, Simon W.,Ouzman, Jacqueline V. A.
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p. 2795 - 2798
(2007/10/03)
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