A protocol for an asymmetric synthesis of γ-amino acids.

A new and practical method for the asymmetric synthesis of γ-amino acids from ß,γ-butenolides by an in situ esterification, condensation, and reduction in a one-pot procedure is described. This method is quite general for the preparation of both enantiomers of aryl or aliphatic γ-amino acids in high yields. These γ-amino-acid derivatives were also shown to be versatile synthetic intermediates for further transformations by their conversion to γ-lactams, δ-amino alcohols, and hydrolysis products in high yields with no racemization.

A facile asymmetric synthesis of either enantiomer of 2-substituted pyrrolidines.

A new and general method for asymmetric synthesis of either enantiomer of 2-substituted pyrrolidines from a single starting material is described. Reductive cyclization of (S(S))-gamma-chloro-N-tert-butanesulfinyl ketimines with LiBHEt(3) in THF at -78 to 23 degrees C afforded (S(S),R)-N-tert-butanesulfinyl-2-substituted pyrrolidines in excellent yields (88-98%) and with high diastereoselectivity (99:1). The diastereoselectivity is controlled effectively by the choice of reducing agent. Thus, the corresponding epimers of (S(S),S)-2-substituted pyrrolidines were synthesized in good yields (87-98%) and with high diastereoslectivity (1:99) by simply switching the reducing agent from LiBHEt(3) to DIBAL-H/LiHMDS. Deprotection of N-tert-butanesulfinyl-2-substituted pyrrolidines using 4 N HCl in dioxane and MeOH gave the corresponding enantiomers of 2-substituted pyrrolidines in quantative yield. This method was found to be effective for a variety of substrates including aromatic, heteroaromatic, and aliphatic substituents. Extension of this methodology to the formation of 2-substituted piperidines is also illustrated. Reductive cyclization of (S(S))-delta-chloro-N-tert-butanesulfinyl ketimine with LiBHEt(3) in THF at -78 to 23 degrees C or DIBAL-H/LiHMDS in toluene at -78 to 0 degrees C afforded the (S(S),R)-N-tert-butanesulfinyl-2-substituted piperidines in excellent yield (98%) and with high diastereoselectivity (99:1) or (S(S),S)-N-tert-butanesulfinyl-2-substituted piperidines in good yield (98%) and with high diastereoselectivity (1:99), respectively.

Nidufexor (LMB763), a Novel FXR Modulator for the Treatment of Nonalcoholic Steatohepatitis.

Farnesoid X receptor (FXR) agonists are emerging as important potential therapeutics for the treatment of nonalcoholic steatohepatitis (NASH) patients, as they exert positive effects on multiple aspects of the disease. FXR agonists reduce lipid accumulation in the liver, hepatocellular inflammation, hepatic injury, and fibrosis. While there are currently no approved therapies for NASH, the bile acid-derived FXR agonist obeticholic acid (OCA; 6-ethyl chenodeoxycholic acid) has shown promise in clinical studies. Previously, we described the discovery of tropifexor (LJN452), the most potent non-bile acid FXR agonist currently in clinical investigation. Here, we report the discovery of a novel chemical series of non-bile acid FXR agonists based on a tricyclic dihydrochromenopyrazole core from which emerged nidufexor (LMB763), a compound with partial FXR agonistic activity in vitro and FXR-dependent gene modulation in vivo. Nidufexor has advanced to Phase 2 human clinical trials in patients with NASH and diabetic nephropathy.

Discovery of novel non-peptidic beta-alanine piperazine amide derivatives and their optimization to achiral, easily accessible, potent and selective somatostatin sst1 receptor antagonists.

Structural simplification of the core moieties of obeline and ergoline somatostatin sst(1) receptor antagonists, followed by systematic optimization, led to the identification of novel, highly potent and selective sst(1) receptor antagonists. These achiral, non-peptidic compounds are easily prepared and show promising PK properties in rodents.

Asymmetric synthesis of homoallylic amines bearing adjacent stereogenic centers by addition of substituted allylic zinc reagents to N-tert-butanesulfinylimines.

A highly diastereoselective addition of substituted racemic allylic zinc reagents to chiral N- tert-butanesulfinylimines resulting in the formation of homoallylic amines is reported. This method is quite general and also efficient for the preparation of enantiomerically pure homoallylic amines bearing quaternary centers and also adjacent quaternary centers.

A scalable synthesis of an azabicyclooctanyl derivative, a novel DPP-4 inhibitor.

A practical synthetic strategy to a chiral azabicycclooctanyl derivative (1), a potent DPP-4 inhibitor, starting from a commercially available nortropine is described. The stereogenic center of 1 was established employing a modified protocol of Ellman's diastereoselective addition of a benzylic nucleophile to tert-butanesulfinimine. Other key steps include Corey-Chaykovsky reaction, Meinwald rearrangement, and CDMT-promoted amide bond formation involving a sterically hindered amine 2.

(R)-2-Phenylpyrrolidine Substituted Imidazopyridazines: A New Class of Potent and Selective Pan-TRK Inhibitors.

Deregulated kinase activities of tropomyosin receptor kinase (TRK) family members have been shown to be associated with tumorigenesis and poor prognosis in a variety of cancer types. In particular, several chromosomal rearrangements involving TRKA have been reported in colorectal, papillary thyroid, glioblastoma, melanoma, and lung tissue that are believed to be the key oncogenic driver in these tumors. By screening the Novartis compound collection, a novel imidazopyridazine TRK inhibitor was identified that served as a launching point for drug optimization. Structure guided drug design led to the identification of (R)-2-phenylpyrrolidine substituted imidazopyridazines as a series of potent, selective, orally bioavailable pan-TRK inhibitors achieving tumor regression in rats bearing KM12 xenografts. From this work the (R)-2-phenylpyrrolidine has emerged as an ideal moiety to incorporate in bicyclic TRK inhibitors by virtue of its shape complementarity to the hydrophobic pocket of TRKs.

An efficient and practical N-methylation of amino acid derivatives.

[reaction: see text] An efficient and practical N-methylation of amino acid derivatives with dimethyl sulfate in the presence of sodium hydride and a catalytic amount of water is described. Reaction of water with sodium hydride generated highly reactive dry sodium hydroxide, which led to much faster reaction rates than powdered sodium hydroxide itself.

Asymmetric synthesis of 2-substituted pyrrolidines by addition of Grignard reagents to gamma-chlorinated N-tert-butanesulfinyl imine.

A highly diastereoselective addition of various Grignard reagents to chiral gamma-chlorinated N-tert-butanesulfinyl imine resulting in the formation of 2-substituted pyrrolidines is reported. This method is general and also efficient for the preparation of both enantiomers of 2-aryl, 2-alkyl and 2-vinyl substituted pyrrolidines in high yields.

Enantioselective hydrogenation of alpha-aminomethylacrylates containing a free NH group for the synthesis of beta-amino acid derivatives.

We describe highly enantioselective synthesis of beta-amino acid derivatives (1a-c) using asymmetric hydrogenation of alpha-aminomethylacrylates (2a-c), which contain a free basic N H group, as the key step. The alpha-aminomethylacrylates (2a-c) were prepared using the Baylis-Hillman reaction of an appropriate aldehyde with methyl acrylate followed by acetylation of the resulting allylic alcohols (4a-b) and S(N)2'-type amination of the allylic acetates (3a-b).

A novel two-carbon homologation with N-vinylacetamides and ethyl vinyl ether as acetaldehyde anion equivalents in the synthesis of 9H-xanthene, 9H-thioxanthene, and 9,10-dihydro-9-acridine carboxaldehydes.

An efficient synthesis of 9H-xanthene-9-carboxaldehyde (3a), 9H-thioxanthene-9-carboxaldehyde (3b), and 9,10-dihydro-10-methyl-9-acridinecarboxaldehyde (3c) by a novel two-carbon homologation of xanthydrol (1a), thioxanthydrol (1b), and 9,10-dihydro-10-methyl-9-acridinol (1c), respectively, using N-vinylacetamides (2a,b) or ethyl vinyl ether (2c) as acetaldehyde anion equivalents, is described.

Palladium-catalyzed amination of aryl bromides with hindered N-alkyl-substituted anilines using a palladium(I) tri-tert-butylphosphine bromide dimer.

An efficient palladium-catalyzed amination of aromatic bromides with hindered N-alkyl-substituted anilines is described, either using the combination of Pd(OAc)(2) and P(t-Bu)(3) or a palladium(I) tri-tert-butylphosphine bromide dimer, [Pd(mu-Br)(t-Bu(3)P)](2), a new, commercially available, and easily handled catalyst.

An efficient and large-scale enantioselective synthesis of PNP405: a purine nucleoside phosphorylase inhibitor.

An efficient and large-scale enantioselective synthesis of PNP405 (1), a purine nucleoside phosphorylase inhibitor, is described. This synthesis of 1 involved eight steps starting from o-fluorophenylacetic acid with a 21.6% overall yield and >99.5% enantiopurity. The key stereogenic center with (R)-configuration was created using Evans' asymmetric alkylation methodology. This synthesis also features the racemization-free reductive removal of the chiral auxiliary in 5 using sodium borohydride, protection of the gamma-cyano alcohol 6 as the trityl ether by a new water-assisted tritylation with trityl chloride and triethylamine or with trityl alcohol and catalytic trifluoroacetic acid, and an efficient one-pot cyclo-guanidinylation of 10 using cyanamide as the guanidinylating agent.