Willis, Anthony C.Banwell, Martin G.White, Lorenzo V.2015-03-102015-03-100385-5414)http://hdl.handle.net/1885/12864The angularly substituted tetrahydrocarbazole 13, which is readily obtained from cyclohexane-1,4-dione monoethylene ketal (6) using Fischer indole chemistry, has been converted into the isothiocyanate 16. Photolysis of this last compound affords, via an intramolecular hetero-[2+2]cycloaddition reaction, the pentacyclic "-thiolactam 17 that incorporates the ABCE ring substructure of natural products 1-3. Attempts to effect a two-carbon homologation of the four-membered ring within compound 17, and thereby establish the D-ring, failed. The azide 20, also obtained from compound 13, forms the cyclic imine 21 on thermolysis in refluxing toluene and the readily derived enamide 23 engages in a Au(I)-catalysed 6-endo-dig cyclisation reaction to give compound 24 embodying the ABCDE ring system of the title alkaloids.This research was funded by the Australian Research Council.18 pages© Copyright 2015 Elsevier B.V.tetrahydrocarbazole 13isothiocyanate 16PhotolysisABCE ring substructuretwo-carbon homologationazide 20compound 13201510.3987/COM-14-S(K)192015-12-10