Asymmetric synthesis, characterization of chiral <i>trans</i> and <i>cis</i>-3-chloro/oxo/thio-4-styryl-<i>β</i>-lactams using (<i>R</i>)-(+)-1-phenylethylamine and their efficient column chromatographic separation
收藏资源简介：
Diverse chiral <i>trans</i> and <i>cis</i>-3-chloro/oxo/thio-4-styryl-<i>β</i>-lactams were efficiently synthesized using chiral 3′-phenylallylidene-[(<i>R</i>)-1′-phenylethyl] amine and substituted ethanoic acids. Moore ketenes derived from chloro/phenythio/benzylthio ethanoic acids (Cl/PhS/BzS) affords both chiral <i>trans</i>- and <i>cis β</i>-lactams, with a preference for <i>trans</i>-stereochemistry. However, Bose-Evans ketenes obtained from 2-methoxy/phenoxyethanoic acids (MeO/PhO), led to the exclusive formation of <i>cis</i>-diastereomers only. Further, individual diastereomers of <i>trans</i>- and <i>cis-β</i>-lactams were separated <i>via</i> efficient column chromatography. The relative <i>cis</i> and <i>trans</i> configuration of the C-3 and C-4 protons in chiral <i>β</i>-lactams was established using coupling constant value ranging from <i>J</i> = 1.4 to 2.1 Hz (in case of <i>trans</i>) and <i>J</i> = 4.3 to 5.2 Hz (in case of <i>cis</i>) respectively. Structural confirmation of <i>β</i>-lactams was done using FT-IR, NMR (<sup>1</sup>H,<sup>13</sup>C,<sup>1</sup>H-<sup>1</sup>H COSY and <sup>1</sup>H-<sup>13</sup>C HSQC), elemental analysis, ESI-MS and X-ray crystallography.
