Total Syntheses of Skyrins

Reprotection with MOMCl gave lactone 821. This was converted with lithium hexamethyldisilazane and the cyclohexenone 818 to the tricyclic species 822. Oxidation with manganese dioxide, followed by dimerization, gave bisanthraquinone 823. Global deprotection with hydrogen chloride yielded (+)-2,2 -ep -cytoskyrin A (824) and (+)-mgulosin A (786a). A crystal structure of the latter is shown in Fig. 12.7. 

The stmcture of the product was proved from its X-ray crystal stmcture, thereby providing evidence that the stmcture of mgulin reported is incorrect (see Fig. 12.8). 

---