Synthesis and acetylcholinesterase inhibitory activity of 2β,3α-disulfoxy-5α-cholestan-6-one

Putting the Puzzle Together To Get the Whole Picture: Molecular Basis of the Affinity of Two Steroid Derivatives to Acetylcholinesterase

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has no cure because its etiology is still unknown, and its main treatment is the administration of acetylcholinesterase (AChE) inhibitors. The study of the mechanism of action of this family of compounds is critical for the design of new more potent and specific inhibitors. In this work, we study the molecular basis of an uncompetitive inhibitor (compound 1, 2β, 3α-dihydroxy-5α-cholestan-6-one disulfate), which we have proved to be a peripheral anionic site (PAS)-binding AChE inhibitor. The pipeline designed in this work is key to the development of other PAS inhibitors that not only inhibit the esterase action of the enzyme but could also modulate the non-cholinergic functions of AChE linked to the process of amylogenesis. Our studies showed that 1 inhibits the enzyme not simply by blocking the main gate but by an allosteric mechanism. A detailed and careful analysis of the ligand binding position and the protein dynamics, particularly regarding their secondary gates and active site, was necessary to conclude this. The same analysis was executed with an inactive analogue (compound 2, 2β, 3α-dihydroxy-5α-cholestan-6-one). Our first computational results showed no differences in affinity to AChE between both steroids, making further analysis necessary. This work highlights the variables to be considered and develops a refined methodology, for the successful design of new potent dual-action drugs for AD, particularly PAS inhibitors, an attractive strategy to combat AD.

Control of the stereochemistry of C14 hydroxyl during the total synthesis of withanolide E and physachenolide C

The stereochemical outcome of the epoxidation of Δ_14–15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the β face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation.

The epoxide configuration in oxidation of C14–C15 alkenes is determined by the configuration of the C17 substituent.

Synthesis of ergostane-type brassinosteroids with modifications in ring A

Herein, we present a new strategy for the preparation of a broad range of brassinosteroid biosynthetic precursors/metabolites differing by the ring A fragment. The protocol is based on the use of readily available phytohormones of this class bearing a 2α,3α-diol moiety (epibrassinolide or epicastasterone) as starting materials. The required functionalities (Δ2-, 2α,3α- and 2β,3β-epoxy-, 2α,3β-, 2β,3α-, and 2β,3β-dihydroxy-, 3-keto-, 3α- and 3β-hydroxy-, 2α-hydroxy-3-keto-) were synthesized from 2α,3α-diols in a few simple steps (Corey-Winter reaction, epoxidation, oxidation, hydride reduction, etc.).

Synthesis of sulfated brassinosteroids

A number of water soluble sulfates of 24-epibrassinolide including the 2α,3α-disulfate and all possible monosulfates were synthesized. The target compounds were isolated in crystalline form as the corresponding sodium salts. Pyridine-sulfur trioxide complex was used as sulfating agent followed by transformation of the resulting pyridinium salts into the sodium sulfates by treatment with NaOH. The control of the regioselectivity was achieved by an appropriate use of acetyl and benzyl protecting groups.

Polyhydroxylated sulfated steroids derived from 5α-cholestanes as antiviral agents against herpes simplex virus

Twelve polyhydroxylated sulfated steroids synthesized from a 5α-cholestane skeleton with different substitutions in C-2, C-3 and C-6 were evaluated for cytotoxicity and antiviral activity against herpes simplex virus (HSV) by a virus plaque reduction assay. Four compounds elicited a selective inhibitory effect against HSV. The disodium salt of 2β,3α-dihydroxy-6E-hydroximine-5α-cholestane-2,3-disulfate, named compound 7, was the most effective inhibitor of HSV-1, HSV-2 and pseudorabies virus (PrV) strains, including acyclovir-resistant variants, in human and monkey cell lines. Preliminary mechanistic studies demonstrated that compound 7 did not affect the initial steps of virus entry but inhibited a subsequent event in the infection process of HSV.

Synthesis of (2β,3α,6-²H₃cholesteryl linoleate and cholesteryl oleate as internal standards for mass spectrometry

The accurate analysis of trace component in complex biological matrices requires the use of reliable standards. For liquid chromatography/mass spectrometry analysis, the stable isotope-labeled derivatives of the analyte molecules are the most appropriate internal standards. We report here the synthesis of (2β,3α,6-(2)H3)cholesteryl linoleate and oleate containing three non-exchangeable deuterium in the steroid ring. The principal reactions used were: (1) trans diaxial opening of 2α,3α-epoxy-6-oxo-5α-cholestane with LiAlD4 and subsequent oxidation of the resulting (2β,6α-(2)H2)-3α,6β-diol with Jones' reagent, followed by reduction of the resulting (2β-(2)H)-3,6-dione with NaBD4 leading to the (2β,3α,6α-(2)H3)-3β,6β-dihydroxy-5α-cholestane, (2) selective protection of the 3β-hydroxy group as the tert-butyldimethylsilyl ether, (3) dehydration of the 6β-hydroxy group with POCl3 and removal of tert-butyldimethylsilyloxy groups with 5M HCl in acetone, and (4) esterification of the resultant (2β,3α,6-(2)H3)cholesterol with linoleic and oleic acids using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide. The isotopic purity was found to be satisfactory by mass spectrometry, and nuclear magnetic resonance properties of the new compounds were tabulated. The labeled compounds can be used as internal standards in liquid chromatography/mass spectrometry assays for clinical and biochemical studies.

Synthesis and cytotoxic evaluation of four new 6E-hydroximinosteroids

Four new 6E-hydroximinosteroids (1, 2a, 3 and 4) have been synthesized from the corresponding ketones, 2β,3β-dihydroxy-5α-cholestan-6-one (5), 2α,3α-dihydroxy-5α-cholestan-6-one (6), 2β,3α-dihydroxy-5α-cholestan-6-one (7) and 2β,3α-dihydroxy-5α-cholestan-6-one-disulfate (8). The cytotoxic activity of the steroidal oximes was evaluated against two prostate carcinoma cell lines (PC-3 and LNCaP) and compared with that of five polyhydroxylated sulfated analogs (8-12). Oxime 3 and trisulfated analog 11 were the most active compounds with IC50 values of 10.8μM (PC-3) and 7.9μM (LNCaP), respectively.

Preparation, anticholinesterase activity and molecular docking of new lupane derivatives

A set of twenty one lupane derivatives (2-22) was prepared from the natural triterpenoid calenduladiol (1) by transformations on the hydroxyl groups at C-3 and C-16, and also on the isopropenyl moiety. The derivatives were tested for their inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and some structure-activity relationships were outlined with the aid of enzyme kinetic studies and docking modelization. The most active compound resulted to be 3,16,30-trioxolup-20(29)-ene (22), with an IC50 value of 21.5μM for butyrylcholinesterase, which revealed a selective inhibitor profile towards this enzyme.

Recent advances in cholesterol chemistry

This review article presents advances in cholesterol chemistry since 2000. Various transformations (chemical, enzymatic, electrochemical, etc.) of cholesterol are presented. A special emphasis is given to cholesterol oxidation reactions, but also substitution of the 3β-hydroxyl group, addition to the C5-C6 double bond, C-H functionalization, and C-C bond forming reactions are discussed.

Synthesis and acetylcholinesterase inhibitory activity of polyhydroxylated sulfated steroids: structure/activity studies

Disulfated and trisulfated steroids have been synthesized from cholesterol and their acetylcholinesterase inhibitory activity has been evaluated. In our studies we have found that the activity was not only dependent on the location of the sulfate groups but on their configurations. 2β,3α,6α-trihydroxy-5α-cholestan-6-one trisulfate (18) was the most active steroid with an IC50 value of 15.48 μM comparable to that of 2β,3α-dihydroxy-5α-cholestan-6-one disulfate (1). Both compounds were found to be less active than the reference compound eserine. The butyrylcholinesterase activity of 1 and 18 was one magnitude lower than that against acetylcholinesterase revealing a selective inhibitor profile.