Action of Nitrating Mixtures and Mineral Acids on the Quinoline Alkaloids Haplophyllidine and Anhydroperforine

The effects of various acids on the intramolecular cyclization of haplophyllidine (1) were studied. Compound1 was converted at room temperature by H2SO4, HNO3, HClO4, and a nitrating mixture into anhydroperforine (2) whereas AcOH and HCl (35%) did not affect1. Nitration of1 and2 at 65 –70°C led to elimination of MeOH followed by aromatization of ring A and nitration of the furan ring to form 7-methoxy-3,3-dimethyl-9-nitro-2,3-dihydro-1H-furo[2,3-b]pyrano[2,3-h] quinoline (3) and 7-methoxy-3,3-dimethyl-9-nitro-2,3,8,9-tetrahydro-1H-furo[2,3-b]pyrano[2,3-h]quinolin-8-ol (4). Use of Ac2O and HNO3 gave 4,8-dimethoxy-8-(3-methylbut-2-en-1-yl)-5,6,7,8-tetrahydro-furo[2,3-b]quinolin-7-yl nitrate (5). The structures of the synthesized compounds were elucidated using 1D and 2D NMR spectral data, X-ray crystal structure analyses, and DFT quantum chemical methods in the B3LYP/6-31g(d) approximation to calculate the UV and circular dichroism (ECD) spectra of4.

Source: Chemistry of Natural Compounds - January 29, 2024 Category: Chemistry Source Type: research