The Partial Synthesis of 16-epi-Pleiocarpamine

Sakai, Shin‐ichiro; Shinma, Nobuo

doi:10.3987/r-1976-05-0985

Cited by 25 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The total synthesis of (+)-macroline 2 has been completed and coupled with natural pleiocarpamine, consequently a partial synthesis of villalstonine 4a has been achieved coupled with its previous conversion into epipleiocarpamine/pleiocarpamine by Sakai constituted a formal total synthesis of pleiocarpamine 6 and villastonine 4a…”

Section: Introductionmentioning

confidence: 99%

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

et al. 2003

View full text Add to dashboard Cite

The first stereospecific, enantiospecific total synthesis of the ring-A oxygenated sarpagine indole alkaloids (+)-N(a)-methylsarpagine (8), (+)-majvinine (14), and (+)-10-methoxyaffinisine (49), as well as the first total synthesis of the Alstonia bisindole alkaloid macralstonidine (9), has been accomplished. This approach employed the Schöllkopf chiral auxiliary for the stereospecific construction of the desired d-(+)-tryptophan unit required for the asymmetric Pictet-Spengler reaction. In addition, the strategy was doubly convergent for the enolate-mediated Pd(0) coupling process and the asymmetric Pictet-Spengler reaction can be employed to synthesize both macroline (2) and N(a)-methylsarpagine (8), the coupling of which provides macralstonidine (9). This approach to ring-A substituted alkoxyindole alkaloids should find wide application for the synthesis of other alkaloids for it is stereospecific and either enantiomer can be prepared with ease.

show abstract

Section: Introductionmentioning

confidence: 99%

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

et al. 2003

View full text Add to dashboard Cite

show abstract

“…Synthetic approaches toward mavacuran are even more limited . Notably, the group of Sakai and then that of Harley‐Mason used a sequence of oxidative chlorination of C16, followed by a nucleophilic substitution by N1, performed on a substrate lacking the CD ring junction, to take advantage of the greater flexibility. During the preparation of the present manuscript, Takayama and co‐workers reported a racemic synthesis of mavacuran alkaloids using a metal carbenoid cyclization of a 16‐deformyl‐geissoschizine‐type structure bearing a carbenoid at C16 .…”

Section: Methodsmentioning

confidence: 99%

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for Enantioselective Total Synthesis of Mavacuran Alkaloids

et al. 2019

View full text Add to dashboard Cite

Reported is the enantioselective total syntheses of mavacuran alkaloids, (+)‐taberdivarine H, (+)‐16‐hydroxymethyl‐pleiocarpamine, and (+)‐16‐epi‐pleiocarpamine, and their postulated biosynthetic precursor 16‐formyl‐pleiocarpamine. This family of monoterpene indole alkaloids is a target of choice since some of its members are subunits of intricate bisindole alkaloids such as bipleiophylline. Inspired by the biosynthetic hypothesis, an oxidative coupling approach from the geissoschizine framework to form the N1−C16 bond was explored. Quaternization of the aliphatic nitrogen center was key to achieving the oxidative coupling induced by KHMDS/I2 as it masks the nucleophilicity of the aliphatic nitrogen center and locks in the required cis conformation.

show abstract

“…The key bioinspired oxidative couplings have been achieved synthetically on a few occasions (Scheme ). In their pioneering work, Sakai and co‐workers adopted a two‐stage approach to form the N1−C16 bond of 3 ,. Oxidative chlorination of the C16 carbon atom of 1 , followed by a nucleophilic substitution of 2 , was performed on a substrate lacking the CD ring junction in order to have more flexibility.…”

Section: Methodsmentioning

confidence: 99%

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for the Total Synthesis of (−)‐17‐nor‐Excelsinidine

et al. 2018

View full text Add to dashboard Cite

We report the first total synthesis of (À)-17-norexcelsinidine,azwitterionic monoterpene indole alkaloid that displays an unusual N4ÀC16 connection. Inspired by the postulated biosynthesis,w ee xplored an oxidative coupling approach from the geissoschizine framework to forge the key ammonium-acetate connection. Tw os trategies allowed us to achieve this goal, namely an intramolecular nucleophilic substitution on a1 6-chlorolactam with the N4 nitrogen atom or ad irect I 2 -mediated N4ÀC16 oxidative coupling from the enolate of geissoschizine.Geissoschizine seems,i ntuitively,t ob ea tt he common biosynthetic origin of several families of monoterpene indole alkaloids [1] through unsolved oxidative cyclizations.T hese umpolung processes involve the C16 carbon atom of the formyl methyl ester [2] and the N1 nitrogen atom for mavacuran alkaloids (e.g., pleiocarpamine), the C7 carbon atom for akuammilan alkaloids (e.g., rhazimal, rhazimol, akuammiline,a nd strictamine), or the N4 nitrogen atom for the recently discovered zwitterionic compounds excelsinidine and 17-nor-excelsinidine,w hich is also known as singaporentinidine in its protonated form (Scheme 1). [3] Theinterconnections and mechanisms for interconversion between these families of alkaloids are not completely understood or proven. Whereas divergent direct oxidative couplings between C16 and N1 or C7 or N4 are possible, [2a] it has also been postulated that the akuammilan skeleton could be the biogenetic precursor of both the mavacuran [2c] and the excelsinidine frameworks. [3d] Theakuammilans have been the subject of very intense synthetic efforts,and several members of this family have succumbed to total synthesis in the last decade. [4,5] Thes ynthesis of mavacurans has also been well studied over the years. [6] Thek ey bioinspired oxidative couplings have been achieved synthetically on af ew occasions (Scheme 2). In their pioneering work, Sakai and co-workers adopted at wostage approach to form the N1 À C16 bond of 3. [6a,b] Oxidative chlorination of the C16 carbon atom of 1,f ollowed by anucleophilic substitution of 2,was performed on asubstrate lacking the CD ring junction in order to have more flexibility. More recently,Maand co-workers developed adirect strategy based on the deprotonation of both the malonate and the NH moiety of the indole of 4 followed by an oxidation of the resulting dianion with I 2 into ab iomimetic bisradical intermediate. [5] Importantly,t of avor the C7 À C16 oxidative coupling (e.g., 5 from 4 with R = H), af ree alcohol is required to form ac helated anion at C7. [5b] Otherwise,t he N1ÀC16 bond is formed (e.g. 6 from 4 with R = TBS and 8 from 7). [5b, 6d] In contrast, no synthetic work has been reported towards the excelsinidines,w hich contain ab ridged bicyclic ammonium moiety.T herefore,inline with our interest in the chemistry of monoterpene indole alkaloids, [7] we herein report our endeavors towards the total synthesis of these natural products with an emphasis on the formation of the key N4ÀC16 bond over the N1À...

show abstract

The Partial Synthesis of 16-epi-Pleiocarpamine

Cited by 25 publications

References 0 publications

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for Enantioselective Total Synthesis of Mavacuran Alkaloids

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for the Total Synthesis of (−)‐17‐nor‐Excelsinidine

Contact Info

Product

Resources

About

The Partial Synthesis of 16-epi-Pleiocarpamine

Cited by 25 publications

References 0 publications

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-Na-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-Na-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for Enantioselective Total Synthesis of Mavacuran Alkaloids

Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for the Total Synthesis of (−)‐17‐nor‐Excelsinidine

Contact Info

Product

Resources

About

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine

The Enantiospecific, Stereospecific Total Synthesis of the Ring-A Oxygenated Sarpagine Indole Alkaloids (+)-Majvinine, (+)-10-Methoxyaffinisine, and (+)-N_a-Methylsarpagine, as Well as the Total Synthesis of the Alstonia Bisindole Alkaloid Macralstonidine