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The title compound, C26H38O6, has a cis junction between two of the six-membered rings (A and B). All three of the six-membered rings have chair conformations that are slightly flattened and the five-membered ring has an unusual 13β-envelope conformation. The 7α and 12α ring substituents are both axial and the 3α and 17β groups are equatorial and pseudo-equatorial, respectively. The 3α-formyloxy group is involved in one weak intermolecular C—H...O bond, which links the molecules into dimers in a head-to-head fashion.

The molecule of the title compound, C23H40O4Si2, features an approximate non-crystallographic C2 symmetry axis. The aldehyde group is disordered over two positions with similar occupancies. The geometry of the isolated molecule was studied by ab initio quantum mechanical calculations employing a molecular orbital Hartree-Fock method. The calculations reproduce well the equilibrium geometry but slightly overestimate the value of the Si-O bond lengths of the trioxadisilepine ring.

The title compound, C21H32O4 crystallizes in a triclinic unit cell, which is very unusual for steroids. The asymmetric unit contains two independent mol­ecules with almost identical geometry, although they are slighly twisted in opposite directions. These mol­ecules form a dimer inter­connected via hydrogen bonds. Both mol­ecules have a cis A/B ring junction characteristic of a 5β-configuration, but differ in the orientation of their hydroxyl groups.

The title compound, C25H34O6, has a 3β,21-configuration, with the epoxy O atom at 16α,17α. Rings A and C have chair conformations which are slightly flattened. Because of the presence of a double bond, ring B assumes an 8β,9α-half chair conformation. Ring D has a conformation close to a 14α-envelope. Cohesion of the crystal can be attributed to van der Waals interactions and weak C—H⋯O interactions.

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 [Csp2—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.

In the title compound, C20H26O2, which is the 6-methylene derivative of androstenedione and a synthetic percursor of exemestane, the steroidAring approximates to a sofa (or envelope) conformation, with the methylene group adjacent to the link to theBring lying out of the plane of the other atoms. TheBandCrings have slightly flattened chair conformations and theDring 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.

The ring conformation of the title compound, C19H30O3, is similar to that of the 5α-epimer except for the cis A/B ring junction. Ring D adopts a 13β,14α-half chair conformation. The mol­ecules are linked together by a two-dimensional network of hydrogen bonds involving the carbonyl and hydroxyl groups.

The title compound, C25H36O5, has two independent mol­ecules in the asymmetric unit with similar geometry. The main difference between the two mol­ecules relates to the conformation of the 17β-methyl ketone and 3β-acetoxy groups, the latter being disordered in one of the mol­ecules. The five-membered ring adopts an unusual 13β-envelope conformation.

The title compound, C(19)H(30)O(4), is an androstan-17-one derivative synthesized from the dehydro-epiandrosterone through a sequential addition of an oxidant, followed by a trans-diaxial opening of the epoxide generated, with Bi(OTf)(3) (OTf is trifluoro-methane-sulfonate). The six-membered rings have a slightly flattened chair conformation, while the five-membered ring adopts a 14-α envelope conformation. All rings are trans fused. In the crystal, the mol-ecules are connected by O-H⋯O hydrogen bonds involving the hydroxyl and carbonyl groups, forming a three-dimensional network. A quantum mechanical ab initio Roothan Hartree-Fock calculation of the free mol-ecule gives bond lengths, valency angles and ring torsion angles of the free molecule at equilibrium geometry (energy minimum) close to the experimental values.

In the title compound, C23H34O4, the two saturated six-membered rings have slightly flattened chair conformations and the unsaturated ring assumes a 8β,9α-half chair conformation distorted towards a 8β-sofa. The five-membered ring has an unusual conformation close to a 13β-envelope. The acetoxy and methyl ketone substituents are twisted with respect to the average molecular plane of the steroid nucleus. The mol­ecules are hydrogen-bonded head-to-head via the hydroxy and methyl ketone groups forming dimers, which are stacked in planes perpendicular to the b axis.

The title compound, C23H32O4, has a 3β configuration, with the epoxy O atom at 16α,17α. Rings A and C have slightly distorted chair conformations. Because of the presence of the C5=C6 double bond, ring B assumes an 8β,9α-half-chair conformation slightly distorted towards an 8β-sofa. Ring D has a conformation close to a 14α-envelope. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The conformation of the mol­ecule is compared with that given by a quantum chemistry calculation using the RHF–AM1 (RHF = Roothaan Hartree–Fock) Hamiltonian model. Cohesion of the crystal can be attributed to van der Waals interactions and weak intermolecular C—H⋯O interactions, which link the mol­ecules head-to-tail along [101].

In the title 6–6–6–5 fused ring compound, C19H28O, all the ring junctions are trans. The unsaturated ring A shows a conformation intermediate between a 10β-sofa and a 1α,10β-half-chair.

The ring conformation of the title compound, 3α,4β-di-hydroxy-5a-androstan-17-one, C 19 H 30 O 3 , is similar to that of the 5β-epimer except for the trans A/B ring junction and the geometry of ring D, which adopts a slightly deformed 13,14-half-chair conformation instead of the more common 14α-envelope conformation. The molecules are linked together by a two-dimensional network of hydrogen bonds involving the carbonyl and hydroxyl groups.

The dihedral angles between ring planes of the title compound, C 19 H 26 O 4 , a D-ring lactone, indicate a slightly curved molecular profile. All ring junctions are trans. A hydrogen bond between the hydroxyl group of ring A and the carbonyl group of ring D links the molecules head-to-tail in helical chains parallel to the 2 1 screw axis along a.

The title compound, C23H32O4, has a 3β configuration, with the epoxy O atom at 16α,17α. Rings A and C have slightly distorted chair conformations. Because of the presence of the C5=C6 double bond, ring B assumes an 8β,9α-half-chair conformation slightly distorted towards an 8β-sofa. Ring D has a conformation close to a 14α-envelope. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The conformation of the mol­ecule is compared with that given by a quantum chemistry calculation using the RHF–AM1 (RHF = Roothaan Hartree–Fock) Hamiltonian model. Cohesion of the crystal can be attributed to van der Waals interactions and weak intermolecular C—H⋯O interactions, which link the mol­ecules head-to-tail along [101].

In the crystal structure of the title compound, C(21)H(32)O(2), ring A is highly distorted, with a conformation inter-mediate 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 acet-oxy substituent. Cohesion of the crystal structure is due only to weak van der Waals inter-actions.

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.

The title compound, C 23 H 34 O 6 , a ring D lactone, has two acetoxy groups in positions 3α and 4β. All ring junctions are trans which results in a planar molecule. The two acetoxy groups have different behaviour, one of them being disordered and exhibiting double-bond delocalization. The ordered acetoxy group is involved in two weak intramolecular C-H… O bonds.

The title compound, C 19 H 26 O 4 , has a C5 atom with an unusual environment, which leads to a molecular 5α configuration. Ring A is highly flattened. The carbaldehyde group is slightly disordered, with interchange of the H and O positions.

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.

The ring conformation of the title compound, 3α,4β-di-hydroxy-5a-androstan-17-one, C 19 H 30 O 3 , is similar to that of the 5β-epimer except for the trans A/B ring junction and the geometry of ring D, which adopts a slightly deformed 13,14-half-chair conformation instead of the more common 14α-envelope conformation. The molecules are linked together by a two-dimensional network of hydrogen bonds involving the carbonyl and hydroxyl groups.

The molecule of the title compound, C23H40O4Si2, features an approximate non-crystallographic C2 symmetry axis. The aldehyde group is disordered over two positions with similar occupancies. The geometry of the isolated molecule was studied by ab initio quantum mechanical calculations employing a molecular orbital Hartree-Fock method. The calculations reproduce well the equilibrium geometry but slightly overestimate the value of the Si-O bond lengths of the trioxadisilepine ring.

In the title compound, C15H7F5O2, an intra­molecular C—H⋯O hydrogen bond induces coplanarity of the central chain and the phenyl ring. An inter­molecular C—H⋯O hydrogen bond leads to the formation of a dimer.

The title compound, alternatively called 24-nor-5 beta-chol-22-ene-3 beta,7 alpha,12 alpha-triyl triformate, C(26)H(38)O(6), has a cis junction between two of the six-membered rings. All three of the six-membered rings have chair conformations that are slightly flattened and the five-membered ring has a 13 beta,14 alpha-half-chair conformation. The 3 beta, 7 alpha and 12 alpha ring substituents are axial and the 17 beta group is equatorial. The 3 beta-formyloxy group is involved in one weak intermolecular C-H...O bond, which links the molecules into dimers in a head-to-head fashion.

The title compound, C(21)H(32)O(3), 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 acet-oxy substituent, and shows a very short Csp(3)-Csp(3) bond next to the epoxide ring, which is characteristic of 3-4 epoxides. .

The dihedral angles between ring planes of the title compound, C 19 H 26 O 4 , a D-ring lactone, indicate a slightly curved molecular profile. All ring junctions are trans. A hydrogen bond between the hydroxyl group of ring A and the carbonyl group of ring D links the molecules head-to-tail in helical chains parallel to the 2 1 screw axis along a.