Improved synthesis of proline-derived Ni(II) complexes of glycine: versatile chiral equivalents of nucleophilic glycine for general asymmetric synthesis of alpha-amino acids.
A synthetically practical and operationally convenient method for preparing (S)-2-[N-(N'-benzylprolyl)amino]benzophenone (BPBP) and hitherto unknown (S)-2-[N-(N'-benzylprolyl)amino]-4-methylbenzophenone (4-Me-BPBP), (S)-2-[N-(N'-benzylprolyl)amino]-5-nitrobenzophenone (5-NO(2)-BPBP), and their corresponding Ni(II) complexes with glycine [GlyNi(II)BPBP], a widely used chiral equivalent of nucleophilic glycine, and new analogues [GlyNi(II)-4-Me-BPBP] and [GlyNi(II)-5- NO(2)-BPBP] is described. The key step of the method is the synthetically efficient amid bond formation between the corresponding o-aminobenzophenones, featuring significant steric shielding and low nucleophilicity of the amino functionality as well as sterically constrained (S)-N-benzylproline (BP).
Ueki
Hisanori
H
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA.
Ellis
Trevor K
TK
Martin
Collin H
CH
Boettiger
Tomas U
TU
Bolene
Shawna B
SB
Soloshonok
Vadim A
VA
D000596:Amino Acids / Q000138:chemical synthesis*; D005998:Glycine / Q000737:chemistry*; D007202:Indicators and Reagents; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D009532:Nickel / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D000596:Amino Acids; D007202:Indicators and Reagents; D008024:Ligands; D009532:Nickel; D011392:Proline; D005998:Glycine