Syntheses of (+)-30-epi-, (-)-6-epi-, (±)-6,30-epi-13,14-didehydroxyisogarcinol and (±)-6,30-epi-garcimultiflorone A utilizing highly diastereoselective, Lewis acid-controlled cyclizations

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.R01 GM073855 - NIGMS NIH HHS; R24 GM111625 - NIGMS NIH HHS; R35 GM118173 - NIGMS NIH HH

Syntheses of (+)-30-<i>epi</i>-, (−)-6-<i>epi</i>‑, (±)-6,30-<i>epi</i>-13,14-Didehydroxyisogarcinol and (±)-6,30-<i>epi</i>-Garcimultiflorone A Utilizing Highly Diastereoselective, Lewis Acid-Controlled Cyclizations

The first syntheses of 13,14-didehydroxyisogarcinol (<b>6</b>) and garcimultiflorone A (<b>5</b>) stereoisomers are reported in six steps from a commercially available phloroglucinol. Lewis acid-controlled, diastereoselective cationic oxycyclizations enabled asymmetric syntheses of (−)-6-<i>epi</i>-<b>6</b> and (+)-30-<i>epi</i>-<b>6</b>. A similar strategy enabled production of the <i>meso</i>-dervied isomers (±)-6,30-<i>epi</i>-<b>6</b> and (±)-6,30-<i>epi-</i><b>5</b>. 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

Asymmetric Syntheses of the Flavonoid Diels–Alder Natural Products Sanggenons C and O

Metal-catalyzed, double Claisen rearrangement of a bis-allyl­oxy­flavone has been utilized to enable a concise synthesis of the hydro­benzo­furo­[3,2-<i>b</i>]­chrom­enone core structure of the natural products sanggenon A and sanggenol F. In addition, catalytic, enantio­selective [4+2] cyclo­additions of 2′-hydroxy­chalcones have been accomplished using B­(OPh)₃/BINOL complexes. Asymmetric syntheses of the flavonoid Diels–Alder natural products sanggenons C and O have been achieved employing a stereo­divergent reaction of a racemic mixture (stereodivergent RRM) involving [4+2] cycloaddition