organic compounds
Reversible prototropic shifts from a stable 14-membered ring macrocycle (4Z,10E,12Z)-[1R*,14S*]-1,8,8-tris(methoxycarbonyl)-5-methyl-3,17- dioxobicyclo[12.3.0]heptadeca-4,10,12-triene, C24H30O8, occurred when the compound was heated to form rac-(5Z,11Z,13Z)-1,8,8-tris(methoxycarbonyl)-5-methyl-3,17-dioxobicyclo[12.3.0]heptadeca-5,11,13-triene, C24H30O8. The resulting compound crystallizes in a highly disordered fashion. After a transannular Diels-Alder reaction, the resulting adduct rac-3,3-bis(methoxycarbonyl)-18- oxo-5α,9β-androst-6-en-11,17-dione, C24H30O8, was then easily converted to a 5α-steroid core, rac-3,3-bis(methoxycarbonyl)-18-oxo-5α-androst-6-en-11,17-dione, C24H30O8. The final adduct is an highly advanced intermediate for the total synthesis of naturally occurring aldosterone.