Km. Aubart et Ch. Heathcock, A biomimetic approach to the discorhabdin alkaloids: Total syntheses of discorhabdins C and E and dethiadiscorhabdin D, J ORG CHEM, 64(1), 1999, pp. 16-22
The characteristic spirodienone structure of the discorhabdin alkaloids is
readily formed by reaction of the tryramine-substituted indoloquinonimines
26, 35, and 36 with cupric chloride, triethylamine, and oxygen. This cycliz
ation provides a possibly biomimetic route to discorhabdins C and E (41 and
42). The unbrominated spirodienone 40 reacts with hydrogen over Pd/C to gi
ve enone 46. Bromination at the a position gives a mixture of bromoenones t
hat undergo smooth conversion to dethiadiscorhabdin D (4) upon treatment wi
th basic alumina.