Chromium tricarbonyl complexes of methyl O-methylpodocarpate: differentiation of diastereomers by high field NMR spectroscopy

摘要: Abstract The reaction of Cr(CO)6 with methyl O-methylpodocarpate yields diastereomeric complexes in which the Cr(CO)3 fragment binds to either α- or β-face aromatic C ring diterpenoid. These isomers are separable using reverse phase high pressure liquid chromatography and their 1H 13C NMR spectra have been recorded at 500 125 MHz, respectively. By use 1H1H COSY 1H13C shift-correlated two-dimensional all protons carbons free ligand both unambiguously assigned. β-Cr(CO)3 can be clearly differentiated on basis MHz spectra. Protons proximal metal markedly deshielded if they lie negative region cone anisotropy carbonyl ligands. changes conformation diterpene skeleton detectable by correlate very well X-ray crystallographic data. Analogies drawn between structures podocarpate those related estrogenic steroids.