E. J. Tavares da Silva

3α,4β-Dihydroxy-5α-androstan-17-one

The crystal structure of the title compound, C 19 H 30 O 3 , is reported. This steroid was obtained as an intermediate in the synthesis of formestane. The molecules are held together by a network of hydrogen bonds involving the carbonyl and hydroxyl groups.

3α,4α-Ep­oxy-5α-androstan-17β-yl acetate

The title compound, C21H32O3, results from modifications of the A and D rings of the aromatase substrate androstenedione. Ring A adopts a conformation between 10β-sofa and 1α,10β half-chair. Rings B and C are in slightly flattened chair conformations. Ring D approaches a 13β-envelope conformation, probably due to the acetoxy substituent, and shows a very short Csp 3—Csp 3 bond next to the epoxide ring, which is characteristic of 3–4 epoxides. .

17-Oxo-5α-androstane-3α, 4β-diyl diacetate and 17-oxo-5β-androstane-3α, 4β-diyl diacetate

The title compounds, both C23H34O5, are the 5alpha and 5beta configurations of two diacetate epimers. The 5beta-diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 A(3), responsible for clathrate behaviour. The 5beta-epimer also features some shorter than average bond lengths in the 3alpha,4beta-acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through ab initio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C-H...O interactions.

3α-Hydroxy-5α-androstane-4,17-dione

The asymmetric unit of the title compound, C 19 H 28 O 3 , contains two independent molecules with almost identical geometry. The molecules have a planar 5a configuration as a result of a trans-A/B junction of the rings. The compound crystallizes in a triclinic cell, which is unusual for steroids. The molecules are linked head-to-tail via hydrogen bonds between the ring A hydroxyl group and the ketone group of ring D, forming two independent chains running along the c axis.

3α,4α-Epoxy-5α-androstan-17-one

The structure of the title compound, 3α,4α-epoxy-5α-androstan-17-one, C19H28O2, shows evidence of the strain caused by the presence of an epoxy O atom bonded to C3 and C4 in the molecule. Ring A has a sizeable distortion and assumes a conformation intermediate between 10-β-sofa and 1,10-half chair. Ring D has a 14-α-envelope conformation. Cohesion of the crystal is due only to van der Waals interactions and weak intermolecular C—H⋯O interactions.

6-Methyl­ideneandrost-4-ene-3,17-dione

In the title compound, C20H26O2, which is the 6-methylene derivative of androstenedione and a synthetic percursor of exemestane, the steroid A ring approximates to a sofa (or envelope) conformation, with the methylene group adjacent to the link to the B ring lying out of the plane of the other atoms. The B and C rings have slightly flattened chair conformations and the D ring is an envelope, with the CH group forming the flap. In the crystal, molecules are linked by two distinct C—H⋯O hydrogen bonds, involving acidic H atoms close to C=C and C=O double bonds.

N-Hexyl-3-(4-hy­droxy-3,5-dimeth­oxy­phen­yl)propanamide

In the title compound, C17H27NO4, which is an hydrosinapic acid derivative with increased lipophilicity conferred by an additional alkyl chain, the central and the hexyl linear chains contain slightly shorter bond lengths [C—N = 1.316 (2) Å; average linear chain C—C = 1.487 (6) Å] than reported average values [Csp 2—N = 1.334, C—C for CH2—CH2 = 1.524 and 1.513 Å for CH2—CH3]. The 4-hydroxy-3,5-dimethoxyphenyl plane [r.m.s. deviation 0.055 (12) Å] makes an angle of 59.89 (5)° with the central plane of the molecule (composed of the N atom, the carbonyl group and the two methylene C atoms linking the carbonyl group and the ring, [r.m.s. deviation 0.0026 (10) Å], which, in turn, makes an angle of 64.24 (13)° with the essentially planar hexyl chain [r.m.s. deviation 0.035 (18) Å]. The N—H group of the amide group is involved in a bifurcated hydrogen bond towards the hydroxy and one of the methoxy O atoms of the 4-hydroxy-3,5-dimethoxyphenyl substituent of a neighbouring molecule, forming a two-dimensional network in the (100) plane. In addition, the same hydroxy group acts as a donor towards the carbonyl O atom of another neighbouring molecule, forming chains running along the b axis.

5α-Androst-3-en-17β-yl acetate

In the crystal structure of the title compound, C21H32O2, ring A is highly distorted, with a conformation intermediate between 10β-sofa and 1α,10β-half chair; rings B and C have slightly flattened chair conformations. Ring D assumes an unusual 13β-envelope conformation, probably induced by the acetoxy substituent. Cohesion of the crystal structure is due only to weak van der Waals interactions.

5α-Androst-3-en-17-one oxime

The title compound, C(19)H(29)NO, is a C17-oxime derivative of a potent aromatase inhibitor, which surprisingly has been found to have no inhibitory power. It crystallizes with two independent molecules in the asymmetric unit. C=N-O-H...N hydrogen bonds link pairs of molecules to form dimers almost parallel to the bc plane. Cohesion of the structure is also due to another three C-H...O hydrogen bonds directed along the a axis. This hydrogen-bonding scheme can be correlated to the almost complete loss of inhibitory power of the title compound.

3,17-Dioxoandrost-4-en-4-yl acetate.

The title compound, C(21)H(28)O(4), has a 4-acetoxy substituent positioned on the steroid alpha face. The six-membered ring A assumes a conformation intermediate between 1alpha,2beta-half chair and 1alpha-sofa. A long Csp(3)-Csp(3) bond is observed in ring B and reproduced in quantum-mechanical ab initio calculations of the isolated molecule using a molecular-orbital Hartree-Fock method. Cohesion of the crystal can be attributed to van der Waals interactions and weak C-H...O hydrogen bonds.