Preparation of tricyclic lactam model compounds of renieramycin and saframycin anticancer natural products from common intermediate

Tricyclic lactam model compounds of the left half (ABC ring) of renieramycin and saframycin anticancer natural products were prepared from common intermediate 6a. Readily available alcohol 6a was converted into enamide 8, and this was followed by transformation into 6b through a hydrobromination reaction in a stereoselective manner. Some diastereomers at C-6 to C-11a of the tricyclic lactam model compounds having several functional groups at C-6 were prepared from 6a or 6b in good yields. We presented also an unexpected reductive acetylation of the p-quinone to produce the corresponding 3,4-dehydro derivative.