Biologically Active Aspidofractinine, Rhazinilam, Akuammiline, and Vincorine Alkaloids from <i>Kopsia</i>

Subramaniam, G.; Hiraku, Osamu; Hayashi, Masahiko; Koyano, Takashi; Komiyama, Kanki; Kam, Toh‐Seok

doi:10.1021/np0703747

Cited by 134 publications

(104 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Notably, ψ-akuammigine (9) contains an additional ring that forms a complex [3.2.1]-bridged oxabicyclic motif. The second group is composed of the furanoindolinecontaining akuammilines and is represented by aspidophylline A (10), 12 aspidodasycarpine (11), 13 and aspidophylline B (12). 14 Members of this group contain an oxygen linkage between C5 and C2 as a salient feature of their furanoindoline cores but lack the N4−C5 bond found in the parent methanoquinolizidine akuammilines.…”

Section: ■ Introductionmentioning

confidence: 99%

Fischer Indolizations as a Strategic Platform for the Total Synthesis of Picrinine

et al. 2015

View full text Add to dashboard Cite

Picrinine, which is a member of the akuammiline family of alkaloids, was first isolated in 1965 from the leaves of Alstonia scholaris. The natural product possesses a daunting polycyclic skeleton that contains a furanoindoline, a bridged [3.3.1]azabicycle, two N,O-acetal linkages, and six stereogenic centers. These structural features render picrinine a challenging and attractive target for total synthesis. This paper provides a full account of our synthetic forays toward picrinine, which culminates in the first total synthesis of this long-standing target. Central to the success of our approach is the use of the Fischer indolization reaction to introduce the C7 quaternary stereocenter and the indoline nucleus of the natural product's scaffold. We probe some of the subtleties of this classic transformation by examining some of the most complex Fischer indolization substrates to date. Additionally, we describe various roadblocks encountered in our experimental efforts, which were successfully overcome to complete the total synthesis of picrinine.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

Fischer Indolizations as a Strategic Platform for the Total Synthesis of Picrinine

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Alkaloids 5−8 were dihydroindole derivatives with the same extended fused ring system, which is a new skeleton. HREIMS of 5−8 provided molecular formulas of C 20 (M + 366.1977), and C 21 H 24 N 2 O 4 (M + 368.1720), respectively. The aromatic proton and carbon resonances (HSQC and HMBC) indicated that 5 was a 12-hydroxy-N-acyldihydroindole derivative, 6 was a 12-hydroxy-10-methoxy-N-acyldihydroindole derivative, 7 was a 12-hydroxy-N-butanoyldihydroindole derivative, and 8 was a 12-hydroxy-11-methoxy-N-acyldihydroindole derivative ( Table 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Indole Alkaloids from Geissospermum reticulatum

et al. 2012

View full text Add to dashboard Cite

Ten indole alkaloids were isolated from Geissospermum reticulatum, seven (1-7) from the leaves and three (8-10) from the bark. Seven were aspidospermatan-type alkaloids (1-3, 5-9), including four (5-8) with a 1-oxa-3-cyclopentene group in their molecule, which we named geissospermidine subtype. Compounds 1-3, 5-8, and 10 had not been reported previously as natural products, while 4 and 9 were the known alkaloids O-demethylaspidospermine and flavopereirine. Their structures were determined by spectroscopic techniques including 1D and 2D NMR experiments (COSY, NOESY, HSQC, HMBC). Additionally, X-ray crystallographic analyses of 1, 2, and 6 were performed. Antiparasitic activities of the ethanolic and alkaloidal extracts and of the pure alkaloids were tested against Trypanosoma cruzi and Leishmania infantum. In general, the extracts exhibited selective action and were more active against Leishmania than against Trypanosoma. Alkaloid 4 was also very active against L. infantum.

show abstract

“…Crocacins were found to exhibit moderate antibacterial, antifungal, and cytotoxic activity. The synthesis of the dienamide moiety of the natural product was performed via a one-pot palladium-catalyzed sequence involving a hydrostannylation and a Stille coupling of 52 with (E)-iodoacrylamide (53). This one-pot procedure circumvented the purification of the intermediate vinylstannane 54, avoiding the partial protodestannylation of the product.…”

Section: Total Synthesis Of Various Classes Of Natural Productsmentioning

confidence: 99%