Steroidal seven-membered A-ring epoxy lactones by oxidation of the corresponding Δ4-3-ketosteroids

Abstract Treatment of Δ 4 -3-ketosteroids with m- chloroperbenzoic acid at 0 °C produced the corresponding steroidal seven-membered A-ring epoxy lactones. The adopted procedure allowed for efficient recovery and separation of the products with definite stereochemistry.