Chartelline alkaloids

Baran PS, Shenvi RA, Mitsos CA (2005) A Remarkable Ring Contraction En Route to the Chartelline Alkaloids. Angew Chem IntEd 44 3714... 

In addition, there are many important nonantibiotic uses of 2-azetidinones in fields ranging from enzyme inhibition [15-21] to gene activation [22], Systems containing one carbon atom common to two rings, spirocyclic compounds, represent an important structural organization. Spirocyclic p-lactams (Fig. 3) behave as p-tum mimetics [23-26] as well as enzyme inhibitors [27, 28], they are precursors of a,a-disubstituted p-amino acids [29-32], and the spiranic p-lactam moiety is present in chartellines and chartelamides [33-38], a family of marine natural products. Synthetic studies and biosynthetic speculation inspired by an unexpected reaction on the marine alkaloid chartelline C have been described [38],... 

Kajii S, Nishikawa T, Isobe M (2008) Chem Commun 3121, Synthetic studies and biosynthetic speculation inspired by an unexpected reaction on the marine alkaloid chartelline C have been described... 

Unique /3-lactam indole alkaloids, namely, chartellines A (77) (87), B (78), and C (79), methoxydechlorochartelline A (80) (88), and chartella-mides A (81) and B (82) (89), were isolated from a marine bryozoan (Chartella papyracea) collected in North Britanny waters. The structure of chartelline A (77) was confirmed by X-ray analysis, and the absolute... 

Scheme 12. Alkaloids from Chartella papyracea. At left, chartelline A, B, C, and methoxy-dechlo-rochaitelline A. At right chartellamide A and B.

A review of the Pummerer reaction describes much of the breadth of this work [18], but a more recent paper expanded this chemistry to form spirocycles which contain adjacent quaternary carbons [20]. While the test cases (22 to form the spirocycle 23) proceeded smoothly, the application to a more complicated structure (24), which would be closer to the ring system seen in the natural product, crassanine, demonstrated that a nearby amine would interfere with the addition of the silyl enol ether as a nucleophile. While this precludes the utility of this reaction for the crassanine alkaloids, the unusual ring formed in 25, a C-3-azetidine spirocyclic indolenine, is found in the chartelline alkaoids. 

The securines, securamines, chartellines, and chartellamides are members of a structurally unique class of natural products isolated from the bryozoa Chartella papyracea and Securiflustra securifrons by Christophersen and coworkers [65-69] (Fig. 7). Chartellines represent a small family of marine-derived, architecturally unique alkaloids that include chartelline A, chartelline B, and chartelline C, which only differ in the number and position of bromines. Chartelline C (173) is composed of indolenine, imidazole, and jS-lactam heterocycles arrayed in a dense, Ji-stacking framework that poses an obvious challenge for its synthesis [70, 71], Though numerous efforts have been made towards chartelline C (173), rally Baran and coworkers have reported its synthesis [70, 71]. 

Anthoni U, Chevolot L, Larsen C, Nielsen PH, Christophersen C (1987) Marine alkaloids. 12. Chartellines, halogenated (3-lactam alkaloids from the marine Bryozoan Chartella papyracea. J Org Chem 52 4709 712... 

Anthoni, U., Chevolot, L., Larsen, C., Nielsen, P. H., Christophersen, C. Marine alkaloid s. 12. chartellines, halogenated y0-lactam alkaloids from the marine bryozoan Chartella papyracea. J. Org. Chem. 1987, 52, 4709-4712. 

Black, P. J., Hecker, E. A., Magnus, P. Studies towards the synthesis of the marine alkaloid chartelline C. Tetrahedron Lett. 2007, 48, 6364-6367. 

Kajii, S., Nishikawa, T., Isobe, M. Synthetic studies and biosynthetic speculation on marine alkaloid chartelline. Chem. Commun. 2008,27, 3121-3123. 

Lin, X.C. and Weinreb, S.M. (2001) Model studies on total synthesis of the chartellines, spirocyclic -lactam alkaloids from a marine bryozoan. Tetrahedron Lett., 42,2631-2633. 

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