95. Total syntheses of clavine alkaloids by an intramolecular nitrone-olefin cycloaddition reaction
    Oppolzer, W.; Grayson, J. I.; Wegmann, H.; Urrea, M.
    Tetrahedron 1983, 39, 3695-3705

The racemic ergot alkaloids chanoclavine I (1) and 6,7-secoagroclavine (4) have been synthesized stereoselectively from indole-4-carboxaldehyde (7) in overall yields of 14and 13%, respectively. Further syntheses of isochanoclavine I (2), paliclavine (5) and costaclavine (6), via the same isoxazolidine 18 are described. The key step 16→18(Scheme 4) involves a transient nitrone 17 which undergoes a kinetically controlled, regio- and stereoselective intramolecular cycloaddition to a 1,2-disubstituted olefinic bond.

DOI : 10.1016/S0040-4020(01)88608-7