Synthesis of Swinhoeisterol A, Dankasterone A and B, and Periconiastone A by Radical Framework Reconstruction
F.L. Duecker, R.C. Heinze, P. Heretsch – 2020
A switchable radical framework reconstruction approach to structurally unique 13(14→8),14(8→7)diabeo-steroid swinhoeisterol A was developed. The conversion of an ergostane skeleton proceeded through the intermediacy of a 13(14→8)abeo-framework as present in the dankasterone and periconiastone family of natural products and features a β scission of a 14-alkoxy radical with concomitant generation of the C8−C13 bond. From this intermediate, and dependent on the conditions employed, the cascade continues with a Dowd–Beckwith rearrangement and leads to the formation of the 13(14→8),14(8→7)diabeo-framework of the swinhoeisterol class of natural products. The synthesis of these frameworks then allowed for efficient access to swinhoeisterol A (1), dankasterone A (Δ4-2), dankasterone B (2), and periconiastone A (3).