title: Synthesis and stereochemical analysis of β-nitromethane substituted γ-amino acids and peptides.
abstract: The high diastereoselectivity in the Michael addition of nitromethane to α,β-unsaturated γ-amino esters, crystal conformations of β-nitromethane substituted γ-amino acids and peptides are studied. Results suggest that the N-Boc protected amide NH, conformations of α,β-unsaturated γ-amino esters and alkyl side chains play a crucial role in dictating the high diastereoselectivity of nitromethane addition to E-vinylogous amino esters. Investigation of the crystal conformations of both α,β-unsaturated γ-amino esters and the Michael addition products suggests that an H-C(γ)-C(β)=C(α) eclipsed conformer of the unsaturated amino ester leads to the major (anti) product compared to that of an N-C(γ)-C(β)=C(α) eclipsed conformer. The major diastereomers were separated and subjected to the peptide synthesis. The single crystal analysis of the dipeptide containing β-nitromethane substituted γ-amino acids reveals a helical type of folded conformation with an isolated H-bond involving a nine-atom pseudocycle.
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune-411 008, India.
authors.forename: Mothukuri
authors.initials: M
authors.lastname: Ganesh Kumar
authors.forename: Sachitanand M
authors.initials: SM
authors.lastname: Mali
authors.forename: Hosahudya N
authors.initials: HN
authors.lastname: Gopi
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D008958:Models, Molecular; D009595:Nitroparaffins / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D004952:Esters; D009595:Nitroparaffins; D010455:Peptides; D008697:Methane; C008640:nitromethane