Syntheses of (+)-30-epi- (−)-6-epi- (±)-630-epi-1314-Didehydroxyisogarcinol and (±)-630-epi-Garcimultiflorone A Utilizing Highly Diastereoselective Lewis Acid-Controlled Cyclizations

摘要

The first syntheses of 13,14-didehydroxyisogarcinol (>6) and garcimultiflorone A (>5) stereoisomers are reported in six steps from a commercially available phloroglucinol. Lewis acid-controlled, diastereoselective cationic oxycyclizations enabled asymmetric syntheses of (−)-6-epi->6 and (+)-30-epi->6. A similar strategy enabled production of the meso-dervied isomers (±)-6,30-epi->6 and (±)-6,30-epi->5. Finally, a convenient strategy for gram scale synthesis was developed utilizing diastereomer separation at a later stage in the synthesis that minimized the number of necessary synthetic operations to access all possible stereoisomers.