A simple, efficient access to functionalized pyrrolobenzazepines related to the BBC core of cephalotaxine

Article abstract of DOI:10.1016/S0040-4039(97)00709-0

Tetracyclic nitrile 19a and ester 19b, exhibiting the ABC core of cephalotaxine 1a, were prepared through K-H-induced cyclization of thioimides 14a and 14b, respectively. This new ring-closure methodology proved to he particularly efficient: thus nitrile 19a was obtained in only 7 steps with a 17 % overall yield from commercially available, inexpensive safrole 2.