Diastereoselectivity in the Transannular Diels–Alder Reaction of a trans-trans-trans 14-Membered Macrocycle Leading to Steroids

A novel 14-membered macrocyclic ring with trans-trans-trans triene geometry, trimethyl (4E,10E,12E)-(1R*,14S*)-5-methyl-17-oxobicyclo[12.3.0]heptadeca-4,10,12-trien- 1,8,8-tricarboxylate, C₂₄H₃₂O₇, which usually undergoes a Diels–Alder cycloaddition upon formation has been isolated. From four possible contractions, the transannular reaction produces three adducts from which trimethyl rac-(5β,9β,10α)-17-oxoandrost-6-ene-3,3,18-tricarboxylate, C₂₄H₃₂O₇, was isolated and crystallized.

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