Total synthesis of (+/-)-flustramines A and C, (+/-)-flustramide A, and (-)- and (+)-debromoflustramines A.

Here we describe the efficient total synthesis of the three title hexahydropyrrolo[2,3-b]indole alkaloids and debromo derivative from readily available indolin-3-ones using key domino reactions, olefination−isomerization−Claisen rearrangement (OIC), and reductive cyclization (RC). (±)-Flustramine C (5) was synthesized in five steps from 6-bromoindolin-3-one 9 via a key intermediate 13a. (±)-Flustramine A (1) has been obtained by reduction of flustramide A (6), which has been prepared in five steps from 13a. (±)-Debromoflustramine A (19) was provided in a similar manner from 13b. The (−)- and (+)-enantiomers of 19 were synthesized through optical resolution of (±)-carboxylic acid 17b using (R)-4-phenyloxazolidin-2-one.