Slobodanka Stanković

New D-modified androstane derivatives as aromatase inhibitors☆

Starting from a 16-oximino derivative of 5-androstene the newly-synthesized 16-oximino-17-hydroxy-17-substituted derivatives 2-4 gave by the Beckmann fragmentation reaction the corresponding D-seco derivatives 6-9. Besides, in the case of the 17-hydroxy-17-methyl-16-oximino derivative 2, as a result of the rearrangement, the hydrolysis product 5 of the 16-oximino group with the opposite configuration at the C-17 was obtained. By the Oppenauer oxidation and/or by dehydration of 7 with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ), the corresponding derivatives 12, 13, and 14 were obtained. The structures of 6 and 12 were unambiguously proved by the appropriate X-ray structural analysis. Kinetic analysis for anti-aromatase activity showed that compound 12 expressed the highest inhibition in the denucleated rat ovarian fraction in comparison to other androstene derivatives (IC(50) was 0.42 microM). In comparison to aminoglutethimide (AG) activity, it was 3.5 times lower. The inhibition was competitive, with K(i) of 0.27 microM. Introduction of additional units of unsaturation (compounds 13 and 14) in D-seco derivatives did not increase anti-aromatase activity.

Synthesis, X-ray crystal structures and biological activity of 16-amino-17-substituted-D-homo steroid derivatives.

D-Homo derivatives in the androstane and estrane series, 12-19, were synthesized by a fragmentation-cyclization reaction of 16-oximino-17-hydroxy-17-substituted derivatives 3-9, or by cyclization of the corresponding D-seco derivatives 20-26. The structures were confirmed by X-ray analysis of compounds 12 and 16. Preliminary assessment of inhibitory effects of D-homo derivatives from androstane series towards aromatase, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17 alpha-hydroxylase/C17-20 lyase (P450c17) and 17 beta-HSD indicated much lower inhibitory potential compared to previously tested activity of another type of D-modified steroids, namely D-seco derivatives. Also, assessment of potential antiestrogenic activity of derivatives from estrane series showed absence of such an activity.

Synthesis, structure, and screening of estrogenic and antiestrogenic activity of new 3,17-substituted-16,17-seco-estratriene derivatives.

The starting compound for synthesis of new 16,17-seco-estratriene derivatives was 3-benzyloxy-17-hydroxy-16,17-secoestra-1,3,5(10)-triene-16-nitrile (1b), obtained from estrone in several synthetic steps. 17-Tosyl, -chloro-, bromo-, and -iodo- derivatives 2b, 4b, 5b, and 6b were prepared directly from secocyanoalcohol 1b, while the 17-fluoro-derivative 3b was obtained from tosylate 2b in the reaction with tetrabutyl ammonium fluoride. The corresponding 3-hydroxy derivatives of these compounds were produced by action of hydrogen in presence of Pd/C, except the 3-hydroxy-17-iodo derivative 6a, which was obtained from 3-hydroxy-17-tosyloxy derivative 2a. All the newly synthesized compounds in biological tests on experimental animals exhibited an almost total loss of estrogenic activity, while most of them even prevented the action of endogenous estrogens. On the other hand, most of them, except compounds 3a and 6b, partially hindered the action of estradiol benzoate, behaving as moderate antagonists.

Synthesis and anti-aromatase activity of some new steroidal D-lactones.

Starting from D-seco derivatives of 5-androstene 1-3, the D-homo lactones, 4 and 5, were synthesized. By the Oppenauer oxidation and/or by dehydration of 4 and 5 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil), the corresponding D-lactones 6-12 were obtained. The structures of 6 and 10 were unambiguously proved by the appropriate X-ray structural analysis. Anti-aromatase assay showed that tested compounds possess inhibition potency, however, two to four times smaller (IC50 from 0.2 to 0.7 microM, respectively) in comparison to aminoglutethimide (AG).

A novel rearrangement of steroidal α-hydroxy oximes

Abstract By the action of acidic titanium trichloride upon 16-oximino-17α-benzyl-17β-hydroxy derivatives in the androstane and estrane series the 16-oxo-17β-benzyl-17α-hydroxy derivatives 6 and 7 with inversed configuration at C 17 were obtained. A mechanism for this novel rearrangement is proposed.

Synthesis and unusual beckmann fragmentation reaction of syn-3-Methoxy-6α,17β-Dihydroxyestra-1,3,5(10)-trien-7-one oxime

Abstract Sodium borohydride reduction of anti-3-methoxy-17β-hydroxyestra-1,3,5(10)-trien-6,7-dione 7-oxime (4a) afforded syn-3-methoxy-6α,17β-dihydroxyestra-1,3,5(10)-trien-7-one oxime (5), which in thionyl chloride at −18 °C undenvent Beckmann fragmentation reaction to the unexpected 3-methoxy-6-oxo-17β-hydroxy-6.7-secoestra-1.3.5(10)-trien-7-nitrile (6). A mechanism of this fragmentation process was proposed.

Ozonation of 3β-acetoxy-5α-chloro-cholestane in solution. X-ray study of 3β-acetoxy-5α-chloro-14-cholestene-ozonide.

Abstract A selected saturated steroid derivative has been subjected to ozonation in solution. As the main reaction product 14,15-ozonide has been isolated in crystalline form whose structure has been unambiguously confirmed by the X-ray difraction method.

A novel fragmentation-cyclization reaction of steroidal α-hydroxy oximes

Abstract By a novel “one pot” fragmentation-cyclization reaction 17β-hydroxy-17α-substituted-16-oximino derivatives in the androstane and estrane series were converted to a new type of D-homo derivative.

Synthesis, crystal and molecular structure, and hyperconjugation of the isomeric 17,20-epoxy-17-picolyl derivatives of 5-androstene and 5α-androstane

Abstract Three pairs of isomeric 17,20-epoxy-17-picolyl-derivatives of 5-androstene and 5α-androstane ( 3 – 8 ) have been prepared by an oxidation of 3β-acetoxy-17-picolinylidene-androst-5-ene (2) and 3β-acetoxy-17-picolinylidene-5α-androstane (2) with in situ prepared Cr(VI) oxide-pyridine-complex in methylene chloride at room temperature. X-Ray structural analysis of the suitably crystalline epoxides 5 and 6 revealed the structure of 5 being 17α, 20α-epoxide, while structure of 6 corresponded to 17β, 20β-epoxide. It was proved that in both cases E-geometrical isomers were formed. Based on the deduced absolute stereochemistry of 5 and 6 , the structures of other two pairs ( 3 – 4 , 7 – 8 ) were readily worked out by NMR-spectroscopy. A mechanism of the oxidation reaction was proposed, and some other relevant chemical experiments were described. Finally, an explanation was offered for the observed differences of the relevant bond lengths and dihedral angles in 5 and 6 which indicated a slight σ - π conjugation between the epoxide and the pyridine rings, which might be coupled with long range effect of the C-7 carbonyl group.

17β-Hydroxy-3-methoxyestra-1,3,5(10)-triene-6,7-dione 7-Oxime

X-ray structure analysis of the title compound, C 19 H 23 NO 4 , showed an unexpected anti orientation for the 6-oxo-7-oximino function. After molecular-mechanics calculations, the H atom of the 17-hydroxy moiety, which participates in a strong hydrogen bond formed in the crystalline state, changed its orientation substantially. Some change in the conformation of ring B was also observed.