An efficient enzymatic preparation of 20-pregnane succinates: chemoenzymatic synthesis of 20β-hemisuccinyloxy-5αH-pregnan-3-one

The isolation of novel pregnane steroids from Aglaia pachyphylla Miq. and the cytotoxicity against breast cancer cell lines (MCF-7)

Steroid groups isolated from many plants are known to play a significant role in various biological systems. Therefore, this research aimed to analyze two novel pregnane steroids, pachylenone A (1) and pachylenone B (2), isolated from Aglaia pachyphylla Miq. The cytotoxicity of the steroids was evaluated against MCF-7 breast cancer cell lines with other known steroid compounds, namely 5α-dihydroprogesterone (3), GSD-8 (4), trans-5α-pregn-l7(20)-en-3,16-dion (5), 20β-hydroxy-5αH-pregnan-3-one (6), 3β-hydroxy-5α-pregnan-20-one (7), aglaiasterol B (8), and 2β,3β-dihydroxypregnan-16-one (9). Meanwhile, structural elucidation was achieved through different spectroscopic methods including one and two-dimensional NMR, as well as mass spectroscopy and quantum chemical calculations (TD-DFT and NMR DP4+ probability). The cytotoxic effects of steroid compounds (1-9) on MCF-7 lines were also examined. The results showed that compound 8 had the strongest activity with an IC50 value of 228 μM, followed by compound 6 (IC50 568,76 μM), and pachylenone A (1) (IC50 768.73 μM). As a recommendation for future research, other activities of these compounds should be evaluated.

Bile acids: Lipase-catalyzed synthesis of new hyodeoxycholic acid derivatives

In this work we present an efficient, environmentally friendly approach to the synthesis of a series of hyodeoxycholic acid derivatives applying Biocatalysis. Fifteen acetyl and ester derivatives, twelve of them new, were obtained through an enzymatic strategy in a fully regioselective way and in very good to excellent yield. In order to find the optimal reaction conditions, the influence of several parameters such as enzyme source, alcohol or acylating agent:substrate ratio, enzyme:substrate ratio, temperature and reaction solvent was considered. The excellent results obtained made this procedure very efficient, particularly considering the low amount of enzyme required. In addition, this methodology uses mild reaction conditions and has reduced environmental impact, making biocatalysis a suitable way to obtaining these bile acids derivatives.

Chemical synthesis of 7α-hydroxypregnenolone, a neuroactive steroid that stimulates locomotor activity

7α-Hydroxypregnenolone is an endogenous neuroactive steroid that stimulates locomotor activity. A synthesis of 7α-hydroxypregnenolone from pregnenolone, which takes advantage of an orthogonal protecting group strategy, is described. In detail, the C7-position was oxidized with CrO₃ and 3,5-dimethylpyrazole to yield a 7-keto steroid intermediate. The resulting 7-ketone was stereoselectively reduced to the 7α-hydroxy group with lithium tri-sec-butylborohydride. In contrast, reduction of the same 7-ketone intermediate with NaBH₄ resulted in primarily the 7β-hydroxy epimer. Furthermore, in an alternative route to the target compound, the 7α-hydroxy group was successfully incorporated by direct C-H allylic benzoyloxylation of pregnenolone-3-acetate with CuBr and tert-butyl peroxybenzoate followed by saponification. The disclosed syntheses to 7-oxygenated steroids are amenable to potentially obtain other biologically active sterols and steroids.

New cholic acid derivatives: Biocatalytic synthesis and molecular docking study

A series of cholic acid derivatives was synthesized by enzyme catalysis. Eleven acetyl and ester derivatives of cholic acid, eight of them new compounds, were obtained through regioselective lipase-catalyzed reactions in very good to excellent yield. The influence of various reaction parameters in the enzymatic esterification, acetylation and alcoholysis reactions, such as enzyme source, alcohol or acylating agent: substrate ratio, enzyme: substrate ratio, solvent and temperature, was studied. Moreover, in order to shed light to cholic acid behavior in the enzymatic reactions, molecular docking of the lipase with cholic acid and some derivatives was carried out.

A new strategy for selective targeting of progesterone receptor with passive antagonists

Currently available progesterone (P4) receptor (PR) antagonists, such as mifepristone (RU486), lack specificity and display partial agonist properties, leading to potential drawbacks in their clinical use. Recent x-ray crystallographic studies have identified key contacts involved in the binding of agonists and antagonists with PR opening the way for a new rational strategy for inactivating PR. We report here the synthesis and characterization of a novel class of PR antagonists (APRn) designed from such studies. The lead molecule, the homosteroid APR19, displays in vivo endometrial anti-P4 activity. APR19 inhibits P4-induced PR recruitment and transactivation from synthetic and endogenous gene promoters. Importantly, it exhibits high PR selectivity with respect to other steroid hormone receptors and is devoid of any partial agonist activity on PR target gene transcription. Two-hybrid and immunostaining experiments reveal that APR19-bound PR is unable to interact with either steroid receptor coactivators 1 and 2 (SRC1 and SCR2) or nuclear receptor corepressor (NcoR) and silencing mediator of retinoid acid and thyroid hormone receptor (SMRT), in contrast to RU486-PR complexes. APR19 also inhibits agonist-induced phosphorylation of serine 294 regulating PR transcriptional activity and turnover kinetics. In silico docking studies based on the crystal structure of the PR ligand-binding domain show that, in contrast to P4, APR19 does not establish stabilizing hydrogen bonds with the ligand-binding cavity, resulting in an unstable ligand-receptor complex. Altogether, these properties highly distinguish APR19 from RU486 and likely its derivatives, suggesting that it belongs to a new class of pure antiprogestins that inactivate PR by a passive mechanism. These specific PR antagonists open new perspectives for long-term hormonal therapy.

Structure and bioassay of triterpenoids and steroids isolated from Sinocalamus affinis

Five triterpenoids with a new 25-norfern carbon skeleton (1-5), a lupane triterpenoid (6), and four 20-hydroxyprogesterone acyl esters (7-10), together with 23 known compounds, were isolated from the stem (with skin removed) of Sinocalamus affinis. The absolute configuration of compound 1 was confirmed by single-crystal X-ray crystallographic analysis using anomalous scattering of Cu Kα radiation. Compounds 1-5 exhibited inhibitory activity against protein tyrosine phosphatase 1B.

Lipases in green chemistry: acylation and alcoholysis on steroids and nucleosides

In this article, we describe the application of lipases in acylation and alcoholysis reactions on steroids and nucleosides. In the field of steroids, a variety of acetyl and fatty acid derivatives of androstanes, pregnanes, and cholestanes have been prepared through lipase-catalyzed acylation and alcoholysis reactions taking advantage of the high regio- and stereoselectivity of these enzymes. The substrates as well as the products show a high degree of biological activity as neurosteroids, hormones, and glucocorticoids. The regioselective preparation of diacylated nucleosides by means of an enzymatic alcoholysis allowed the synthesis of nucleosides prodrugs or modified nucleosides. The quantitative full deacylation and dealkoxycarbonylation of nucleosides and steroids is a mild synthetic method for the deprotection of these labile compounds. Some of the reported steroid and nucleoside products are novel, and it is not possible to obtain them satisfactorily by following traditional synthetic procedures. The advantages presented by this methodology, such as selectivity, mild reaction conditions, and low environmental impact, make the lipases an important tool in the application of the principles of Green Chemistry, offering a convenient way to prepare derivatives of natural compounds with a great potential in the pharmaceutical industry.