A new synthetic method toward a key intermediate in the total synthesis of alkannin and shikonin.

In the present work, a new synthetic method toward a key intermediate in the total synthesis of alkannin and shikonin is developed. The key intermediate, 4-methyl-1-(naphtho[1,8- de :4,5- d'e' ]bis([1,3]dioxine)-4-yl)pent-3-en-1-one (5), is synthesized via the reaction of 1,8:4,5-bis(methylenedioxy)naphthalene-2-carboxylic acid N -methoxy- N -methylamide with prenyllithium. This synthetic approach avoids the use of N -methoxy- N,4-dimethylpent-3-enamide, which is not easy to obtain, and the toxic reagent sodium cyanide. [ABSTRACT FROM AUTHOR]