Reversal of absolute stereochemistry of the pyrrolo[2,1-b]quinazoline alkaloids vasicine, vasicinone, vasicinol and vasicinolone

摘要: Abstract The previously assigned 3 R configuration of (−)-vasicinone has been reversed and this pyrrolo[2,1-b]quinazoline-9-one shown to have the S -configuration ( ) on basis an X-ray diffraction study (+)-vasicinone hydrobromide. Likewise, stereochemistry earlier (−)-vasicine (peganine) 1 analysis its hydrochloride also by reinvestigation absolute alkaloids (+)-vasicinol 2 vasicinolone 5 which inter-related, should -configuration. A H nmr spectroscopy use Mosher's method using MTPA [α-methoxy-α-(trifluoromethyl)phenylacetic acid] esters indicated exception model for establishing configuration.