title: Diastereoselective synthesis of 2-amino-4-phosphonobutanoic acids by conjugate addition of lithiated Schöllkopf's bislactim ethers to vinylphosphonates.
abstract: Conjugate additions of lithiated bislactim ethers derived from cyclo-[Gly-Val] and cyclo-[Ala-Val] to alpha-, beta-, or alpha,beta-substituted vinylphosphonates allow direct and stereoselective access to a variety of 3- or 4-monosubstituted and 2,3-, 2,4-, or 3,4-disubstituted 2-amino-4-phosphonobutanoic acids (AP4 derivatives) in enantiomerically pure form. The relative stereochemistry was assigned by X-ray diffraction analysis or NMR study of 1,2-oxaphosphorinane derivatives. Competitive eight-membered "compact" and "relaxed" transition-state structures are invoked to rationalize the stereochemical outcome of the conjugate additions.
mesh_terms: D000613:Aminobutyrates / Q000138:chemical synthesis* / Q000737:chemistry; D004987:Ethers / Q000737:chemistry*; D007769:Lactams / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D063065:Organophosphonates / Q000737:chemistry*; D018094:Receptors, Metabotropic Glutamate / Q000737:chemistry; D013237:Stereoisomerism; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D000613:Aminobutyrates; D004987:Ethers; D007769:Lactams; D063065:Organophosphonates; D018094:Receptors, Metabotropic Glutamate; D014753:Vinyl Compounds; D008094:Lithium