Conjugate addition of lithiated Schollkopf's bislactim ether to 1E,3E-Butadienylphosphonates: Stereocontrolled access to 2,3 -anti-4E 2-Amino-6-phosphono-4-hexenoic acid derivatives

Article abstract of DOI:10.1016/S0040-4039(97)00888-5

Face-selective 1,6-addition of lithiated Schollkopf's bislactime ether 5 to 4-substituted, 1,4- or 3,4-disubstituted 1E,3E-butadienylphosphonates 6a-d allows a direct and stereocontrolled access to semi-rigid AP6 analogues, the 2,3-anti-4E 2-amino-6-phosphono-4-hexenoic acid derivatives 4a-c. The relative stereochemistry was assigned from a NMR study of the cyclic derivative 12c. Tenmembered trans-fused chair-boat-like transition states are invoked to rationalize the stereochemical outcome of the addition.