Synthesis of 10b-fluorinated analogues of protubonine A and its 11a-epimer via fluorocyclisation of tryptophan-containing dipeptides

Abstract

The synthesis of 10b-fluorinated analogues of protubonine A and its 11a-epimer was accomplished using fluorocyclisation of tryptophan-containing dipeptides with N-fluoro-2,4,6-trimethylpyridinium triflate to 3a-fluoropyrrolo[2,3-b]indoles as a key step. Acetylation of the indole nitrogen and the following diketopiperazine formation gave the 10b-fluorinated analogues of protubonine A and its 11a-epimer.