New Rearrangement of an Aspidosperma Alkaloid. The First Biomimetic Entry in the Goniomitine Skeleton

Goniomitine: An Overview on the Chemistry of This Indole Alkaloid

“…This alkaloid was obtained as a result of the attempts to synthesize (+)-goniomitine ( 1 ) from the compound 40 , previously obtained from (−)-vincadifformine ( 2 ) (Scheme 5) [9]. In Scheme 7 are depicted the sequences of reactions that led to the synthesis of compound 45 as well as other alkaloids with tetracyclic skeleton of goniomitine ( 1 ).…”

“…The results from the study of biomimetic transformation of an Aspidosperma alkaloid ( 2 ) into the substances 39 - 40 , with the skeleton of goniomitine ( 1 ), were published in 1995 by Lewin et al [ 9 ]. The sequences of reactions for the discovery of a new biomimetic in vitro rearrangement are depicted in Scheme 5 .…”

“…The sequences of reactions for the discovery of a new biomimetic in vitro rearrangement are depicted in Scheme 5 . Scheme 6 displays the proposed mechanism [ 9 ] for the transformation of compound 36 into the alkaloids 39 and 40 .…”

“…In continuation to the studies of chemical transformations of vincadifformine ( 2 ) into alkaloids analogs to goniomitine ( 1 ), Lewin and Schaeffer [ 10 ] published in 1995 the semisynthesis of (+)-16-hydroxymethyl-goniomitine ( 45 ). This alkaloid was obtained as a result of the attempts to synthesize (+)-goniomitine ( 1 ) from the compound 40 , previously obtained from (−)-vincadifformine ( 2 ) ( Scheme 5 ) [ 9 ]. In Scheme 7 are depicted the sequences of reactions that led to the synthesis of compound 45 as well as other alkaloids with tetracyclic skeleton of goniomitine ( 1 ).…”

Recent developments in syntheses of the post-secodine indole alkaloids. Part III: Rearranged alkaloid types

“…Thus, the acetal ester 1098 was hydrolyzed 49 to hemiacetal 1100 (71%) prior to the crucial exposure to trifluoroacetic acid (TFA/CH 2 Cl 2 1:99, rt 20 min), which could have proceeded through a ring-opening (→ 1101) and loss of hydrogen chloride (an activation of the indole; → 1102), Scheme 22. Subsequent cyclization in the highly conjugated quinonoid imine 1102 by a stereoselective addition to the nitrone could have generated carbocation 1103 which accounts for the formation of both tetracycle 1104 (loss of a proton; 42%) and pentacycle 1105 (oxide addition; 11%).…”