luotonin-a and rutecarpine

The totality of chemical space is so immense that only a small fraction can ever be explored. Computational searching has indicated that bioactivity is associated with a comparatively small number of ring-containing structures. Pyrrole, indole, pyridine, quinoline, quinazoline and related 6-membered ring-containing aza-arenes figure prominently. This review focuses on the search for fast, efficient and environmentally friendly preparative methods for these rings with specific emphasis on iminyl radical-mediated procedures. Oxime derivatives, particularly oxime esters and oxime ethers, are attractive precursors for these radicals. Their use is described in conventional thermolytic, microwave-assisted and UV-vis based preparative procedures. Photoredox-catalyzed protocols involving designer oxime ethers are also covered. Choice can be made amongst these synthetic strategies for a wide variety of 5- and 6-membered ring heterocycles including phenanthridine and related aza-arenes. Applications to selected natural products and bioactive molecules, including trispheridine, vasconine, luotonin A and rutaecarpine, are included.

Topics: Catalysis; Cyclization; Dioxoles; Free Radicals; Indole Alkaloids; Oximes; Phenanthridines; Pyridines; Pyrroles; Quinazolines; Quinones

One-pot synthesis of various 2,3-polymethylene-4(3H)-quinazolinones from anthranilic acid, corresponding lactam and SOCl(2) is described, which can be applicable to the synthesis of simple 4(3H)-quinazolinone-derived alkaloids, such as luotonin A, tryptanthrin, and rutaecarpine.

Topics: Chemical Phenomena; Chemistry, Physical; Indicators and Reagents; Indole Alkaloids; Lactams; Magnetic Resonance Spectroscopy; ortho-Aminobenzoates; Pyrroles; Quinazolines; Quinazolinones; Quinones; Spectrophotometry, Infrared

Alkyl, aryl, heteroaryl and acyl radicals have been cyclised onto the 2-position of 3H-quinazolin-4-one. The side chains containing the radical precursors were attached to the nitrogen atom in the 3-position. The cyclisations take place by aromatic homolytic substitution hence retain the aromaticity of the 3H-quinazolin-4-one ring. The highest yields were obtained using hexamethylditin to facilitate cyclisation rather than reduction without cyclisation. The alkaloids deoxyvasicinone , mackinazolinone , tryptanthrin , luotonin A and rutaecarpine were synthesised by radical cyclisation onto 3H-quinazolin-4-one.

Topics: Alkaloids; Cyclization; Free Radicals; Indole Alkaloids; Molecular Structure; Pyrroles; Quinazolines; Quinazolinones; Quinones