N\u3csup\u3e1\u3c/sup\u3e-Acetyl-3\u27-methylandrosta-4,16-dieno[16,17-\u3cem\u3ed\u3c/em\u3e]pyrazole-3-one

In an attempt to find the structural features promoting the thermal isomerization of the N-acylated steroid [16,17-d]pyrazoles into [17,16-c]pyrazole derivatives,the X-ray structure analysis of the title compound, C23H30N2O3, (1), has been carried out. The steroid moiety of (I) has the usual conformation. The dihedral angle between the planar pyrazole ring and the N-acetyl group is very small [5.6 (2)°], but the amide C-N bond seems to be substantially elongated [1.404 (3) Å ]. The d-pyrazole ring junction via a double bond leads to deformations of some bond and torsion angles, which would be decreased in the case of a ring junction via a single bond in the [17, 16-c]pyrazole isomer

Structure of (22\u3cem\u3eS\u3c/em\u3e)-3\u3cem\u3eβ\u3c/em\u3e-Acetoxy-20-(3-isopropylisoxazolin-5-yl)-4,4,14 \u3cem\u3eα\u3c/em\u3e-trimethylpregn-8(9)-ene

C32H51NO3, Mr = 497·7, orthorhombic, P212121, a = 7·577 (2), b = 10·510 (2), c = 35·399 (7) Å, V = 2819 (1) Å3, Z = 4, Dx = 1·173 g cm-3, λ (Mo Kα) = 0·71073 Å, μ = 0·69 cm-1, F(000) = 1096, T = 153 K, R = 0·0497 for 2235 observed reflections. The compound investigated is found to be a (22S)-epimer

The Structure of 16, 17β-epoxy-17α-pregn-5-en-3β-ol-20-one Monohydrate

The structure of the title compound (1) has been studied by means of X-ray diffraction. The region of cycleD in epoxide1 was compared with that of the 16,17α-epoxy derivatives of progesterone and pregnenolone (studied previously) as well as with that of the respective 16,17α- and 16,17β-cyclopropano analogs. In contrast to the 16,17α-epoxy-20-oxo derivatives, in compound1 the electron conjugation of the epoxide ring with the CH3CO group at C(17) is partly disrupted. Moreover, the steric congestion at C(17) is significantly less pronounced in 16,17β-epoxide1 than in its 16,17α-counterpart. Both of these factors, especially steric decongestion, are favorable for nucleophilic attack at C(17) in the molecule of1. The X-ray diffraction data do not contradict the previously advanced mechanism of epoxide ring opening in 16,17α- and 16,17β-epoxy-20-oxo steroids by nucleophilic reagents

The X-ray Investigation of 16α,17α-Thiazolidine Derivatives of Δ4- and Δ5-Pregnanes and Conformational Analysis of their Oxathiolane Analog

An X-ray study of 3,20-dioxo-4-pregnene-[16α, 17α−d]- -2\u27,2\u27-dimethylthiazolidine (I) and 3β-hydroxy-20-oxo-5- -pregnene-[16α,17α−d]-2\u27,2\u27-dimethylthiazolidine (II) has been carried out. Two independent molecules in crystal II have significantly different conformations of the D and E rings, although according to the atom-atom potential calculations the energy of interaction of these molecules with their neighbors in crystal is the same. The calculation of conformational energy of 3,20-dioxo-4-pregnene-[17α, 16α−d]-2\u27,2\u27- -dimethyloxathiolane (III) by the molecular mechanics method (MMM) indicates a possibility of existence of two similar conformers also for this molecule. The MMM calculation shows also that the conformation of molecule III (as well as progesterone) with the 17β-acetyl group torsion angle C(16)C(17)C(20)O(20) close to -120° is possible