Structure and conformation of 2β,3β-epoxyestr-5(10)-en-1,4, 17-trione, spectroscopic and X-ray crystallographic studies

Abstract

Colourless single crystals were isolated as by-product during the synthesis of steroidal A-ring substituted 1,4-quinones (and epoxyquinols), as synthetic products with antibiotic and antitumor properties. Its structure was proposed by comparing IR, UV, 1 H and 13 C NMR spectra to the ones of quinone 2 and independently determined by an X-ray analysis, as 2β,3β- epoxyestr-5(10)-en-1,4,17-trione. Crystals belong to the monoclinic system with space group P2 1 : a = 6.767(3) Å, b = 7.097(5) Å, c = 15.748(5) Å, β = 97.070(5)°, V = 750.6(8) Å 3 , Z = 2, D(x) = 1.329 Mg m -3 , μ(Mo K(α)) = 0.093 mm -1 . The structure was solved by direct methods and refined to a final R = 0.064 for 1729 reflections with I > 2σ(I). The steroidal skeleton with chiral centre at C 13 possesses the S configuration defining β- orientation of O 2 atom bridging C2 and C3 atoms and β-oriented methyl group bonded to C13 atom. The best plane through the ring A and epoxy ring plane form an angle of 89.6(2)°. Conformational analysis of the steroid rings are performed by calculating the ring puckering parameters and asymmetry factors. The conformation of the A ring is screw-boat 1 S 6 , ring B half-chair 4 H 3 , ring C chair 1 C 4 , and the five-membered D ring is halfchair 2 H 1 conformation. The crystal structure is stabilised by the weak C-H···O hydrogen bonds and Van der Waals interaction. (C) 2000 Elsevier Science B.V.