The synthesis and structure of new vinylogous carbamates of sparteine

Abstract Synthesis of new ( E )-(-)-[2-methyl ( 2 ), ethyl ( 3 ), isopropyl ( 4 ), benzyl ( 5 ) and phenyl ( 6 )] carbonylmethylideno-17-oxosparteine by the Eschenmoser coupling reaction has been described. Stereochemistry of these compounds has been determined by 13 C and 1 H NMR and that of compound 2 additionally by X-ray analysis. The Haasnoot equation has been used to determine the HCCH dihedral angle in ( E )-(-)-2-methyl-(methylcarbonylomethylideno)-17-oxosparteine on the basis of NMR spectroscopy.