NMR determination of molecular stereochemistry of hetero-Diels-Alder reaction products: Comparison with calculation

作者：Yang Y^*; Evilia RF; Huang JK

来源：Spectroscopy Letters, 1998, 31(2): 307-312.

DOI：10.1080/00387019808003255

• NMR
• molecular stereochemistry
• Diels-Alder reactions
• ROSEY
• TOCSY
• NOESY
• molecular simulation

An asymmetric hetero-Diels-Alder cycloadduct (III) is synthesized and isolated. The H-1-H-1 distance between a proton on the C-12 chiral center and an ortho phenyl proton is measured by NMR spectral studies (ROSEY, NOESY, TOCSY) of the reaction product of 2,4-penanedienoic acid-(-)-menthol ester with 4,4 '-dimethoxydiphenythione. The experimentally determined value is compared to the distance computed by molecular modeling software (Sybyl). The agreement between experiment and computation is only fair indicating that the use of such measurements for small molecules of uncertain geometry must be approached with care. The results indicate that the distance of closest approach between two protons in a molecule is more consistent with the NMR determined distance than is the equilibrium, lowest energy form of the molecule.

• 出版日期1998
• 单位中山大学