Epoxidation and reduction of DHEA, 1,4,6-androstatrien-3-one and 4,6-androstadien-3beta,17beta-diol

Design, synthesis, biological activity evaluation and structure-activity relationships of new steroidal aromatase inhibitors. The case of C-ring and 7β substituted steroids

In this work, new steroidal aromatase inhibitors (AIs) were designed, synthesized, and tested. In one approach, C-ring substituted steroids namely those functionalized at C-11 position with an α or β hydroxyl group or with a carbonyl group as well as C-9/C-11 steroidal olefins and epoxides were studied. It was found that the carbonyl group at C-11 is more beneficial for aromatase inhibition than the hydroxyl group, and that the C-ring epoxides were more potent than the C-ring olefins, leading to the discovery of a very strong AI, compound 7, with an IC₅₀ of 0.011 μM, better than Exemestane, the steroidal AI in clinical use, which presents an IC₅₀ of 0.050 μM. In another approach, we explored the biological activity of A-ring C-1/C-2 steroidal olefins and epoxides in relation to aromatase inhibition and compared it with the biological activity of C-ring C-9/C-11 steroidal olefins and epoxides. On the contrary to what was observed for the C-ring olefins and epoxides, the A-ring epoxides were less potent than A-ring olefins. Finally, the effect of 7β-methyl substitution on aromatase inhibition was compared with 7α-methyl substitution, showing that 7β-methyl is better than 7α-methyl substitution. Molecular modelling studies showed that the 7β-methyl on C-7 seems to protrude into the opening to the access channel of aromatase in comparison to the 7α-methyl. This comparison led to find the best steroidal AI (12a) of this work with IC₅₀ of 0.0058 μM. Compound 12a showed higher aromatase inhibition capacity than two of the three AIs currently in clinical use.

Tailoring chemoenzymatic oxidation via in situ peracids

Epoxidation chemistry often suffers from the challenging handling of peracids and thus requires in situ preparation. Here, we describe a two-phase enzymatic system that allows the effective generation of peracids and directly translate their activity to the epoxidation of olefins. We demonstrate the approach by application to lipid and olefin epoxidation as well as sulfide oxidation. These methods offer useful applications to synthetic modifications and scalable green processes.

A stable epoxide of estrone: Evidence for formation of a 'new' estrogen metabolite

Oxidative metabolism of estrogens is an important feature in liver and some non-hepatic tissues. In initial studies on estrogen metabolism in tissues from the reproductive tract of the stallion, where testicular estrogen secretion is remarkably high, a prominent radiolabeled product from [³H]-estrone (E1) was noted on chromatography; it had a retention time (Rt) between 17β-estradiol (E2) and E1. Unexpectedly, when non-radiolabeled E1 was the substrate no UV absorption at 280nm was seen at the Rt for the [³H]-labeled product-suggesting a non-aromatic ring A. The following efforts were made to reveal more about the nature of the "unknown" compound. Reduction and acetylation showed, separately, the presence of a single keto and hydroxyl group. Exposure to acid gave a single radiolabeled peak with Rt of 6α-hydroxy-E1-suggesting the presence of a third molecule of oxygen. Mass spectrometry with limited material was inconclusive but supportive for a formula of C₁₈H₂₂O_3. Thus, an epoxide involving the aromatic ring of E1 is suggested as a labile intermediate in the formation of the "unknown" metabolite. Estrogen epoxides as labile, reactive intermediates have been considered as potential precursors of the 2- and 4-hydroxy catechol estrogens with implications in breast cancer [Soloway, 2007]. Because of the association of the "unknown" metabolite with 6α-hydroxy-E1, the structural form proposed for the stable epoxide is that for 5α,6α-epoxy-estrone. This represents an alternative to the production of the 2- and 4-hydroxy-catechol estrogens. The broad range in normal tissues where the "unknown" compound was shown to be a persistent metabolite (e.g. mouse mammary glands, ovary, uterus, brain, muscle, equine conceptus, stallion and domestic boar reproductive tracts) suggests more general biological implications.

Triterpenoids and an alkamide from Ganoderma tsugae

Ganoderma tsugae is a medicinal mushroom. In a continual study on the bioactive constituents of this fungus, a new lanostanoid, 3β-acetoxy-16α-hydroxy-24ξ-methyl-5α-lanosta-8,25-dien-21-oic acid, named tsugaric acid F (1) and a novel palmitamide, N-(3'α,4'β-dihydroxy-2'β-(hydroxymethyl)-1'β-(cyclobutyl)palmitamide (2) were isolated and characterized from the fruit bodies of G. tsugae, and three novel seco-lanostanoids, 3,4-seco-8α,9α-epoxy-5α-lanosta-21-oic acid 3,4 lactone (5), 3,4-seco-5β-lanosta-7,9(11),4(29)-trien-3,21-dioic acid-3-methyl ester (6), 3,4-seco-5β-lanosta-7,9(11),4(29)-trien-3,21-dioic acid (7), and a known compound, 3-oxo-5α-lanosta-8-en-21-oic acid (4) were prepared from 3. The structures of new compounds, 1, 2, 5-7 were determined by spectroscopic methods. Compounds 1 and 4 showed inhibitory effects on xanthine oxidase (XO) with an IC50 values of 313.3 ± 80.0 and 43.9 ± 29.9 μM, respectively when 7 exhibited potent inhibitory effect on superoxide anion generation in rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP)/cytochalasin B (CB) with an IC50 values of 1.3 ± 0.2 μM. Compounds 4-7 showed weak cytotoxic activities against PC3 cells. These results indicated that 4 and 7 may be used as cancer chemopreventive agents.

Synthesis and 5α-reductase inhibitory activity of C₂₁ steroids having 1,4-diene or 4,6-diene 20-ones and 4-azasteroid 20-oximes

The synthesis and evaluation of 5α-reductase inhibitory activity of some 4-azasteroid-20-ones and 20-oximes and 3β-hydroxy-, 3β-acetoxy-, or epoxy-substituted C₂₁ steroidal 20-ones and 20-oximes having double bonds in the A and/or B ring are described. Inhibitory activity of synthesized compounds was assessed using 5α-reductase enzyme and [1,2,6,7-³H]testosterone as substrate. All synthesized compounds were less active than finasteride (IC₅₀: 1.2 nM). Three 4-azasteroid-2-oximes (compounds 4, 6 and 8) showed good inhibitory activity (IC₅₀: 26, 10 and 11 nM) and were more active than corresponding 4-azasteroid 20-ones (compounds 3, 5 and 7). 3β-Hydroxy-, 3β-acetoxy- and 1α,2α-, 5α,6α- or 6α,7α-epoxysteroid-20-one and -20-oxime derivatives having double bonds in the A and/or B ring showed no inhibition of 5α-reductase enzyme.

Synthesis and screening of aromatase inhibitory activity of substituted C19 steroidal 17-oxime analogs

The synthesis and aromatase inhibitory activity of androst-4-en-, androst-5-en-, 1β,2β-epoxy- and/or androsta-4,6-dien-, 4β,5β-epoxyandrostane-, and 4-substituted androst-4-en-17-oxime derivatives are described. Inhibition activity of synthesized compounds was assessed using aromatase enzyme and [1β-³H]androstenedione as substrate. Most of the compounds displayed similar to or more aromatase inhibitory activity than formestane (74.2%). 4-Chloro-3β-hydroxy-4-androsten-17-one oxime (14, 93.8%) showed the highest activity, while 4-azido-3β-hydroxy-4-androsten-17-one oxime (17, 32.8%) showed the lowest inhibitory activity for aromatase.

Synthesis and antifungal activity of functionalized 2,3-spirostane isomers

Invasive fungal infections are a major complication for individuals with compromised immune systems. One of the most significant challenges in the treatment of invasive fungal infections is the increased resistance of many organisms to widely used antifungals, making the development of novel antifungal agents essential. Many naturally occurring products have been found to be effective antimicrobial agents. In particular, saponins with spirostane glycosidic moieties-isolated from plant or marine species-have been shown to possess a range of antimicrobial properties. In this report, we outline a novel approach to the synthesis of a number of functionalized spirostane molecules that can be further used as building blocks for novel spirostane-linked glycosides and present results from the in vitro screenings of the antifungal potential of each derivative against four fungal species, including Candida albicans, Cryptococcus neoformans, Candida glabrata, and the filamentous fungus Aspergillus fumigatus.

Synthesis of 2- and 7-substituted C19 steroids having a 1,4,6-triene or 1,4-diene structure and their cytotoxic effects on T47D and MDA-MB231 breast cancer cells

2-Chloro-, 2-bromo- and 2-azido-1,4,6-androstatriene-3,17-diones were synthesized from 1α,2α-epoxy-4,6-androstadiene-3,17-dione (2) using HCl, HBr and NaN₃, respectively. Compound 2 was also reacted with NaCN to give 2-cyano-1,4,6-androstatriene-3,17-dione (5) and 2β-cyano-1α-hydroxy-4,6-androstadiene-3,17-dione (6). 6α,7α-Epoxy-1,4-androstadiene-3,17-dione (8) was reacted with HCl, HBr and NaN₃ to form the corresponding 7β-chloro-, 7β-bromo- and 7β-azido-6α-hydroxy-1,4-androstadiene-3,17-diones. The cytotoxic activity of these compounds towards T47D (estrogen-dependent) and MDA-MB231 (estrogen-independent) breast cancer cell lines was evaluated. The 6α-hydroxy-7β-substituted analogs were more active than the 2-substituted analogs on both cell lines. Compound 2 showed the highest selective activity against the T47D (IC₅₀7.1 μM) cell line and 5 showed good cytotoxic activity on MDA-MB231 (IC₅₀18.5 μM) cell line, respectively. The 6α,7α-epoxy analog 8 also showed high cytotoxic activity on both cell lines (IC₅₀ 17.3 μM on T47D and IC₅₀ 26.9 μM on MDA-MB231).

Synthesis of pregnane derivatives, their cytotoxicity on LNCap and PC-3 cells, and screening on 5alpha-reductase inhibitory activity

A series of epoxy- and/or 20-oxime pregnanes were synthesized from commercially available pregnenolone. Compounds 1, 3, 7, 8 and 11-13 were evaluated for cytotoxicity activity towards LNCaP (androgen-dependent) and PC-3 (androgen-independent) prostate cancer cells. Compound 13 showed the highest activity on both LNCaP (IC₅₀ 15.17 μM) and PC-3 (IC₅₀ 11.83 μM) cell lines. Compound 11 showed weak activity on LNCaP cells (IC ₅₀ 71.85 μM) and 8 showed the weak activity on PC-3 cells (IC₅₀ 68.95 μM), respectively. The 5α-reductase II (5AR2) inhibitory effects of compounds 1-3, 5 and 7-13 were investigated in a convenient screening model, in which compounds 5, 8, 11 and 12 were observed to be potential inhibitors of 5α-reductase, in particular, the 4-azasteroid 11, that also inhibited cell proliferation of androgen-dependent cells and 8, that in addition inhibited PC-3 cells more potently than LNCaP cells.

Chemoselective reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by various hydride reagents

The chemoselectivity of rigid cyclic alpha,beta-unsaturated carbonyl group on the reducing agents was influenced by the ring size and steric factor. Cholesterol (cholest-5-en-3beta-ol) and dehydroepiandrosterone (DHEA) were oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione. They were reduced with NaBH(4), lithium tri-sec-butylborohydride (l-Selectride), LiAlH(4), 9-borabicyclo[3.3.1]nonane (9-BBN), lithium triethylborohydride (Super-hydride), and BH(3) x (CH(3))(2)S in various conditions, respectively. Reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by NaBH(4) (4 equiv.) produced 4,6-cholestadien-3beta-ol and 4,6-androstadiene-3beta,17beta-diol, respectively. Reduction by l-Selectride (12 equiv.) afforded 4,6-cholestadien-3alpha-ol and 4,6-androstadiene-3alpha,17beta-diol, chemoselectively. Reaction with Super-hydride (12 equiv.) produced 4,6-cholestadien-3-one and 3-oxo-4,6-androstadien-17beta-ol. Reduction of 1,4,6-cholestatrien-3-one by 9-BBN (14 equiv.) produced 1,4,6-cholestatrien-3alpha-ol, but 1,4,6-androstatriene-3,17-dione was not reacted with 9-BBN in the reaction conditions. Reaction of LiAlH(4) (6 equiv.) formed 4,6-cholestadien-3beta-ol and 3-oxo-1,4,6-androstatrien-17beta-ol. Reduction of 1,4,6-cholestatrien-3-one by BH(3) x (CH(3))(2)S (11 equiv.) gave cholestane as major compound and unlike reactivity of cholesterol, 1,4,6-androstatriene-3,17-dione by 8 equiv. of BH(3) x (CH(3))(2)S formed 3-oxo-1,4,6-androstatrien-17beta-ol. LiAlH(4) and BH(3) x (CH(3))(2)S showed relatively low chemoselectivity.