118248-61-6Relevant articles and documents
Efficient resolution of racemic N-benzyl β3-amino acids by iterative liquid-liquid extraction with a chiral (salen)cobalt(iii) complex as enantioselective selector
Dzygiel, Pawel,Monti, Chiara,Piarulli, Umberto,Gennari, Cesare
, p. 3464 - 3471 (2008/09/20)
The efficient (up to 93% ee) resolution of racemic N-benzyl β3-amino acids has been achieved by an iterative (two cycle) liquid-liquid extraction process using a lipophilic chiral (salen)cobalt(iii) complex [CoIII(1)(OAc)]. As a result of the resolution by extraction, one enantiomer of the N-benzyl β3-amino acid predominated in the aqueous phase, while the other enantiomer was driven into the organic phase by complexation to cobalt. The complexed amino acid was then quantitatively released into an aqueous phase, by a reductive (CoIII → Co II) counter-extraction using l-ascorbic acid. The reductive cleavage allowed for the recovery of the cobalt(ii) selector in up to 90% yield (easily re-oxidable to CoIII with air/AcOH). The Royal Society of Chemistry.
Synthesis and X-ray crystal structure determination of 1,3-bridged β-lactams: Novel, anti-Bredt β-lactams
Williams,Lee,Miller,Anderson
, p. 1073 - 1081 (2007/10/02)
The first successful syntheses of several anti-Bredt β-lactams from alkyl acetoacetate in 11-14 steps are described. The key cyclization reaction involves the Rh(II)-catalyzed carbene insertion of the diazo derivatives 12, 23, and 31 into the N-H bond of the β-lactams. These (±)-1,3-bridged β-lactams have IR absorptions of 1780-1795 cm-1 for the β-lactam carbonyls. The structure of 32d has been determined by X-ray crystallography; this derivative exhibits a C-N (amide) bond length of 1.414 (4) A and a β-lactam pyramid with the nitrogen atom 0.51 A above the basal plane of three carbon atoms.
