Synthesis of two new haptens of 16alpha-hydroxydehydroepiandrosterone (3beta,16alpha-dihydroxyandrost-5-en-17-one)

Probing Steroidal Substrate Specificity of Cytochrome P450 BM3 Variants

M01A82W, M11A82W and M01A82WS72I are three cytochrome P450 BM3 (CYP102A1) variants. They can catalyze the hydroxylation of testosterone (TES) and norethisterone at different positions, thereby making them promising biocatalysts for steroid hydroxylation. With the aim of obtaining more hydroxylated steroid precursors it is necessary to probe the steroidal substrate diversity of these BM3 variants. Here, three purified BM3 variants were first incubated with eight steroids, including testosterone (TES), methyltestosterone (MT), cholesterol, β-sitosterol, dehydroepiandrosterone (DHEA), diosgenin, pregnenolone and ergosterol. The results indicated that the two 3-keto-Δ⁴-steroids TES and MT can be hydroxylated at various positions by the three BM3 mutants, respectively. On the contrary, the three enzymes displayed no any activity toward the remaining six 3-hydroxy-Δ⁵-steroids. This result indicates that the BM3 mutants prefer 3-keto-Δ⁴-steroids as hydroxylation substrates. To further verify this notion, five other substrates, including two 3-hydroxy-Δ⁵-steroids and three 3-keto-Δ⁴-steroids, were carefully selected to incubate with the three BM3 variants. The results indicated the three 3-keto-Δ⁴-steroids can be metabolized to form hydroxysteroids by the three BM3 variants. On the other hand, the two 3-hydroxy-Δ⁵-steroids cannot be hydroxylated at any position by the BM3 mutants. These results further support the above conclusion, therefore demonstrating the 3-keto-Δ⁴–steroid substrate preference of BM3 mutants, and laying a foundation for microbial production of more hydroxylated steroid intermediates using BM3 variants.

Synthesis of a 19-(O-carboxymethyl)oxime hapten of 7β-hydroxy-epiandrosterone

In order to develop an immunoassay of 7β-hydroxy-epiandrosterone, a stereoselective synthesis of a specific hapten, 7β-hydroxy-19-oxo-androstan 19-(O-carboxymethyl)oxime (17), was performed. This synthesis was achieved in 16% overall yield starting from the well-known 3β-acetoxy-19-hydroxy-5-androsten-17-one (1). After coupling of the alkyl oxime moiety, an allylic oxidation of the C-7 carbon under mild conditions followed by two selective reductions established all the functionalities of the final compound 17.

Synthesis of Some Novel 3,3-Ethylenedioxyandrost-7β-Acyloxy-5-Ene-17-One Derivatives as Potent Aromatase Inhibitors

3,3,17,17-Diethylenedioxyandrost-5-ene was obtained by ketalisation of androstenedione, which was oxidised with PDC and t-BuOOH to form 3,3,17,17-diethylene-dioxyandrost-5-ene-7-one. Stereoselective reduction of 3,3,17,17-diethylene-dioxyandrost-5-ene-7-one by NaBH4 in the presence of CeCl3.6H2O gave 3,3,17,17-diethylenedioxy-7β-hydroxy-androst-5-ene, which was deprotected with p-toluenesulfonic acid to gave 3,3-ethylenedioxyandrost-5-ene-7β-hydroxy and androst-4,6-dien-3,17-dione. A series of androstenedione derivatives were obtained from 3,3-ethylenedioxyandrost-5-ene-7β-hydroxy by the esterification reaction. Their structures were confirmed by MS, 1H NMR, 13C NMR and HRMS.

A novel radioimmunoassay of 16alpha-hydroxy-dehydroepiandrosterone and its physiological levels

16alpha-Hydroxy-dehydroepiandrosterone (16alpha-OH-DHEA) belongs to the products of extensive DHEA metabolism in mammalian tissues. It is a precursor of 16alpha-hydroxylated estrogens, increased levels of which are associated with autoimmune disorders. A highly specific radioimmunoassay of unconjugated 16alpha-OH-DHEA was developed and evaluated. Polyclonal rabbit antisera were raised against 3beta,16alpha-dihydroxy-17,19-dione-19-O-(carboxymethyloxime) and 3beta,16alpha-dihydroxy-7,17-dione-7-O-(carboxymethyloxime) BSA conjugates. Two methods were used for preparation of the conjugates. Homologous radioiodinated derivatives with tyrosine methyl ester were prepared as tracers. While antisera to 7-CMO cross-reacted with DHEA as much as by 58%, the cross-reaction of the chosen antiserum prepared via 19-oxogroup by micellar conjugation technique with 16beta-OH-DHEA was only 0.13% and with all other structurally related steroids, including DHEA were lower than 0.01%. The detection limit was 0.017 pmol (5.7 pg)/tube, the average intra- and inter-assay coefficients of variation were 8.2 and 11.4%, respectively. Mean recovery of serum spiked with 16alpha-OH-DHEA varied between 80 and 110%, the results were independent on sample dilution. 16alpha-OH-DHEA concentrations in 18 randomly selected sera, including 6 samples from patients with thyroid cancer were compared with results obtained by earlier GC-MS method. Physiological levels of 16alpha-OH-DHEA in 316 sera (184 females and 132 males) analyzed so far varied between 0.0 and 1.86 nmol/l.

A novel radioimmunoassay of 7-oxo-DHEA and its physiological levels

A novel radioimmunoassay (RIA) of unconjugated 7-oxo-dehydroepiandrosterone (7-oxo-DHEA) in human serum was developed for the first time. This steroid is an intermediate in the biosynthesis of immunomodulatory 7-hydroxylated DHEA metabolites, and has been shown to possess thermogenic properties. The method employs polyclonal rabbit antiserum to (19E)-3beta-hydroxy-7,17,19-trione-19-O-(carboxymethyloxime):BSA conjugate and a homologous radioiodinated derivative with tyrosine methyl ester. The cross reactivity of the antiserum with structurally closest 7-hydroxyepimers of DHEA was lower than 1.7%, with DHEA 0.4%, with all other related steroid less than 0.4%. The method includes ether extraction of serum (0.5 ml), followed by RIA. Its detection limit was 0.06 pmol (18 pg)/tube, the average intra- and inter-assay coefficients of variation were 4.1% and 8.3%, respectively. Mean recovery of serum spiked with 7-oxo-DHEA varied between 78.8% and 112%. Its levels in three serum pools were compared with a low-resolution gas chromatography-mass spectrometry method with satisfactory results. The method has been used for determination of 7-oxo-DHEA in serum samples of 215 subjects (91 males and 124 females) without overt endocrine disorders, aged 5-71 years. The over-all mean+/-S.D. was 0.280+/-0.227, the median 0.239 nmol/l. No significant sex differences were recorded. The only group which differed significantly from all other ones were males below 10 years, significantly lower values than in other age groups were found also in the first two age groups of females.

Steroids: reactions and partial synthesis

This article reviews the progress in the chemistry of the steroids that was published between January and December 2003. The reactions and partial synthesis of estrogens, androgens, pregnanes, cholic acid derivatives, cholestanes and vitamin D analogues are covered. There are 152 references.

Facile synthesis of cids: biotinylated estrone oximes efficiently heterodimerize estrogen receptor and streptavidin proteins in yeast three hybrid systems

[structure: see text] We synthesized estrone oximes as chemical inducers of protein heterodimerization (CIDs). Estrone-17-(O-carboxymethyl)oxime coupled to biotinamidocaproic acid via N,N'-dimethylhexane-1,6-diamine efficiently heterodimerizes estrogen receptors (ERs) and streptavidin Y43A in yeast three hybrid systems, activating gene expression over 100-fold at 10 microM. Related hexane-1,6-diamine and estradiol-6-(O-carboxymethyl)oxime derivatives were ineffective CIDs due to low affinity for ERs when bound to streptavidin. Estrone oximes bind ERs with submicromolar affinity and effectively display small molecules to target proteins expressed in yeast.