Oxazine- and oxazole-fused derivatives of the alkaloid boldine and their complete structural and spectral assignments by HMQC and HMBC experiments

The novel heterocycles 1,11-dimethoxy-2-hydroxy-6-rnethyloxazolo[4,5-k]-5,6,6a,7-tetrahydro-4H-dibenzo [de,g]quinoline, 1,12-dimethoxy-2-hydroxy-6-methyl-9-phenyl-10H-oxazin[5,6-k]-5,6,6a,7- tetrahydro-4H-dibenzo[de,g]quinolin-10-one and 1,11-dimethoxy-2-hydroxy-6-methyl-9-phenyloxazolo[4,5-k]-5,6,6a,7-tetrahydro-4H- dibenzo[de,g]quinoline were prepared starting from the alkaloid boldine. The structures were confirmed and the ¹H and ¹³C NMR spectra were completely assigned using a combination of one- and two-dimensional NMR techniques.