Modeling Possible Biogenetic Pathways to the Isomeric Pyrano[2,3-]indole and Pyrano[3,2-]indole Cores of Certain Prenylated Indole Alkaloids Using Gold(I)-Catalyzed Intramolecular Hydroarylation Reactions.

A significant subset of the so-called prenylated indole alkaloids (PIAs) contains an angularly fused pyrano[2,3-]indole core, while a smaller number embody the isomeric and linearly fused pyrano[3,2-]indole one. In an effort to probe the capacities of intramolecular hydroarylation (IMHA) reactions to allow for the selective formation of one or other of these motifs, a series of 6-((2-methylbut-3-yn-2-yl)oxy)-1-indoles varying in the nature of the substituents at C1-C3 was prepared and subjected to reaction with a range of gold(I) catalysts. In every instance, preferential (but not exclusive) formation of the angularly fused pyrano[2,3-]indole isomer was observed.

Total Syntheses of the Structures Assigned to Denigrins A, B, C, F, and G, 3,4-Diaryl-Pyrrole and -Pyrrolidinone Alkaloids, and the Conversion of Congener B into the Co-metabolite Spirodactylone.

The title marine natural products have been prepared by total synthesis and in the case of congeners , , and for the first time. Each of these was obtained by manipulation of readily prepared denigrin B (). The structure, , assigned to denigrin C is shown to be incorrect.

Total Syntheses of the Structures Assigned to the Marine Natural Products Orthoscuticellines A-E.

The readily prepared and vinylated β-carboline has been converted over one or two steps into compounds -, the structures assigned to the recently reported marine natural products orthoscuticellines A-E. The spectral data recorded on the synthetically derived compounds are fully consistent with the assigned structures and, on making allowances for variations in the pH of the medium in which the spectra of the natural products were recorded, it is concluded that the structures assigned to orthoscuticellines A-E are most likely correct. Certainly, the calculated C NMR spectra of the α-, γ-, and δ-carboline isomers of compounds - suggest that orthoscuticellines A-E do incorporate the assigned β-carboline core.