Synthesis of 12ß-methyl-18-nor-avicholic acid analogues as potential TGR5 agonists.

In the quest for new modulators of the Farnesoid-X (FXR) and Takeda G-protein-coupled (TGR5) receptors, bile acids are a popular candidate for drug development. Recently, bile acids endowed with a C16-hydroxy group emerged as ligands of FXR and TGR5 with remarkable agonistic efficacies. Inspired by these findings, we synthesised a series of C16-hydroxylated 12ß-methyl-18-nor-bile acid analogues from a Δ13(17)-12ß-methyl-18-nor-chenodeoxycholic acid intermediate (16), the synthesis of which we reported previously. The preparation of these aptly named 12ß-methyl-18-nor-avicholic acids (17, 18, 41 and 42) was accomplished via allylic oxidation at C16, hydrogenation of the C13→C17 double bond and selective reduction of the C16-carbonyl group. Described also are various side products which were isolated during the evaluation of methods to affect the initial allylic oxidation. In addition, C23-methyl modified 12ß-methyl-18-nor-bile acids with (48, 49, 51 and 52) and without a C16-hydroxy group (45, 46 and 55), were synthesized to enable comparison of biological activities between these compounds and their un-methylated counterparts. As a result of our investigations we identified (23R)-12ß,23-dimethyl-18-nor-chenodeoxycholic acid (46) and 12ß-methyl-17-epi-18-nor-chenodeoxycholic acid 53 as TGR5 ligands with EC50 values of 25 µM.

C5-Iminosugar modification of casein kinase 1δ lead 3-(4-fluorophenyl)-5-isopropyl-4-(pyridin-4-yl)isoxazole promotes enhanced inhibitor affinity and selectivity.

The quest for isoform-selective and specific ATP-competitive protein kinase inhibitors is of great interest, as inhibitors with these qualities will come with reduced toxicity and improved efficacy. However, creating such inhibitors is very challenging due to the high molecular similarity of kinases ATP active sites. To achieve selectivity for our casein kinase (CK) 1 inhibitor series, we elected to endow our previous CK1δ-hit, 3-(4-fluorophenyl)-5-isopropyl-4-(pyridin-4-yl)isoxazole (1), with chiral iminosugar scaffolds. These scaffolds were attached to C5 of the isoxazole ring, a position deemed favorable to facilitate binding interactions with the ribose pocket/solvent-open area of the ATP binding pocket of CK1δ. Here, we describe the synthesis of analogs of 1 ((-)-/(+)-34, (-)-/(+)-48), which were prepared in 13 steps from enantiomerically pure ethyl (3R,4S)- and ethyl (3S,4R)-1-benzyl-4-[(tert-butyldimethylsilyl)oxy]-5-oxopyrrolidine-3-carboxylate ((-)-11 and (+)-11), respectively. The synthesis involved the coupling of Weinreb amide-activated chiral pyrrolidine scaffolds with 4- and 2-fluoro-4-picoline and reaction of the resulting 4-picolyl ketone intermediates ((-)-/(+)-40 and (-)-/(+)-44) with 4-fluoro-N-hydroxybenzenecarboximidoyl chloride to form the desired isoxazole ring. The activity of the compounds against human CK1δ, -ε, and -α was assessed in recently optimized in vitro assays. Compound (-)-34 was the most active compound with IC50 values (CK1δ/ε) of 1/8 µM and displayed enhanced selectivity toward CK1δ.

The discovery of 12ß-methyl-17-epi-18-nor-bile acids as potent and selective TGR5 agonists.

Recent discoveries have demonstrated that the physiological function of bile acids extends to the regulation of diverse signaling processes through interactions with nuclear and G protein-coupled receptors, most notably the Farnesoid-X nuclear receptor (FXR) and the G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5). Targeting such signaling pathways pharmacologically, i.e. with bile acid-derived therapeutics, presents great potential for the treatment of various metabolic, inflammatory immune, liver, and neurodegenerative diseases. Here we report the discovery of two potent and selective TGR5 agonists (NZP196 and 917). These compounds are the taurine conjugates of 6α-ethyl-substituted 12ß-methyl-18-nor-bile acids with the side chain being located on the α-face of the steroid scaffold. The compounds emerged from a screening effort of a diverse library of 12ß-methyl-18-nor-bile acids that were synthesized from 12ß-methyl-18-nor-chenodeoxycholic acid and its C17-epimer. Upon testing for FXR activity, both compounds were found to be inactive, thus revealing selectivity for TGR5.

3α,7-Dihydroxy-14(13→12)abeo-5ß,12α(H),13ß(H)-cholan-24-oic Acids Display Neuroprotective Properties in Common Forms of Parkinson's Disease.

Parkinson's Disease is the most common neurodegenerative movement disorder globally, with prevalence increasing. There is an urgent need for new therapeutics which are disease-modifying rather than symptomatic. Mitochondrial dysfunction is a well-documented mechanism in both sporadic and familial Parkinson's Disease. Furthermore, ursodeoxycholic acid (UDCA) has been identified as a bile acid which leads to increased mitochondrial function in multiple in vitro and in vivo models of Parkinson's Disease. Here, we describe the synthesis of novel C-nor-D-homo bile acid derivatives and the 12-hydroxy-methylated derivative of lagocholic acid (7) and their biological evaluation in fibroblasts from patients with either sporadic or LRRK2 mutant Parkinson's Disease. These compounds boost mitochondrial function to a similar level or above that of UDCA in many assays; notable, however, is their ability to boost mitochondrial function to a higher level and at lower concentrations than UDCA specifically in the fibroblasts from LRRK2 patients. Our study indicates that novel bile acid chemistry could lead to the development of more efficacious bile acids which increase mitochondrial function and ultimately cellular health at lower concentrations proving attractive potential novel therapeutics for Parkinson's Disease.

Synthesis of 12ß-Methyl-18-nor-bile Acids.

Decoupling the roles of the farnesoid X nuclear receptor and Takeda G-protein-coupled bile acid receptor 5 is essential for the development of novel bile acid therapeutics targeting metabolic and neurodegenerative diseases. Herein, we describe the synthesis of 12ß-methyl-18-nor-bile acids which may serve as probes in the search for new bile acid analogues with clinical applicability. A Nametkin-type rearrangement was applied to protected cholic acid derivatives, giving rise to tetra-substituted Δ13,14- and Δ13,17-unsaturated 12ß-methyl-18-nor-bile acid intermediates (24a and 25a). Subsequent catalytic hydrogenation and deprotection yielded 12ß-methyl-18-nor-chenodeoxycholic acid (27a) and its 17-epi-epimer (28a) as the two major reaction products. Optimization of the synthetic sequence enabled a chromatography-free route to prepare these bile acids at a multi-gram scale. In addition, the first cis-C-D ring-junctured bile acid and a new 14(13 → 12)-abeo-bile acid are described. Furthermore, deuteration experiments were performed to provide mechanistic insights into the formation of the formal anti-hydrogenation product 12ß-methyl-18-nor-chenodeoxycholic acid (27a).