An Efficient Synthesis of an αvβ3 Antagonist

Modular, automated synthesis of spirocyclic tetrahydronaphthyridines from primary alkylamines

Spirocyclic tetrahydronaphthyridines (THNs) are valuable scaffolds for drug discovery campaigns, but access to this 3D chemical space is hampered by a lack of modular and scalable synthetic methods. We hereby report an automated, continuous flow synthesis of α-alkylated and spirocyclic 1,2,3,4-tetrahydro-1,8-naphthyridines ("1,8-THNs"), in addition to their regioisomeric 1,6-THN analogues, from abundant primary amine feedstocks. An annulative disconnection approach based on photoredox-catalysed hydroaminoalkylation (HAA) of halogenated vinylpyridines is sequenced in combination with intramolecular SNAr N-arylation. To access the remaining 1,7- and 1,5-THN isomers, a photoredox-catalysed HAA step is telescoped with a palladium-catalysed C-N bond formation. Altogether, this provides a highly modular access to four isomeric THN cores from a common set of unprotected primary amine starting materials, using the same bond disconnections. The simplifying power of the methodology is illustrated by a concise synthesis of the spirocyclic THN core of Pfizer's MC4R antagonist PF-07258669.

Thermodynamic Understanding of an Aza-Michael Reaction Enables Five-Step Synthesis of the Potent Integrin Inhibitor MK-0429

We describe a general strategy for the aza-Michael addition of nucleophilic heterocycles into β-substituted acrylates using potassium tert-butoxide as catalyst. Demonstrating that the reaction is under thermodynamic control underpins optimization efforts and enables rapid exploration of the substrate scope, with yields ranging from 55% to 94%. We further leverage these lessons in a significantly shortened synthesis of MK-0429, a potent pan-integrin inhibitor previously taken into human clinical trials for the treatment of prostate cancer and osteoporosis.

Discovery of Roblitinib (FGF401) as a Reversible-Covalent Inhibitor of the Kinase Activity of Fibroblast Growth Factor Receptor 4

FGF19 signaling through the FGFR4/β-klotho receptor complex has been shown to be a key driver of growth and survival in a subset of hepatocellular carcinomas, making selective FGFR4 inhibition an attractive treatment opportunity. A kinome-wide sequence alignment highlighted a poorly conserved cysteine residue within the FGFR4 ATP-binding site at position 552, two positions beyond the gate-keeper residue. Several strategies for targeting this cysteine to identify FGFR4 selective inhibitor starting points are summarized which made use of both rational and unbiased screening approaches. The optimization of a 2-formylquinoline amide hit series is described in which the aldehyde makes a hemithioacetal reversible-covalent interaction with cysteine 552. Key challenges addressed during the optimization are improving the FGFR4 potency, metabolic stability, and solubility leading ultimately to the highly selective first-in-class clinical candidate roblitinib.

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner-Wadsworth-Emmons-based approach

Integrin inhibitors based on the tripeptide sequence Arg-Gly-Asp (RGD) are potential therapeutics for the treatment of idiopathic pulmonary fibrosis (IPF). Herein, we describe an expeditious three-step synthetic sequence of Horner-Wadsworth-Emmons olefination, diimide reduction, and global deprotection to synthesise cores for these compounds in high yields (63-83% over 3 steps) with no need for chromatography. Key to this transformation is the phosphoramidate protecting group, which is stable to metalation steps.

A Direct Approach to Orthogonally Protected α-Amino Aldehydes

O-Neopentyl-xanthate 19 bearing a masked α-amino aldehyde, with the two functional groups orthogonally protected, reacts cleanly with many functional alkenes. The radical addition-transfer furnishes densely functionalized adducts that can be further transformed into an array of amino-substituted carbocycles and heteroaromatics. They are also easily converted into imidazolones.

Synthesis and determination of absolute configuration of a non-peptidic αvβ6 integrin antagonist for the treatment of idiopathic pulmonary fibrosis

Integrin inhibitor (cell adhesion assays) pIC₅₀ α_vβ₆ = 8.4, α_vβ₃ = 6.0, α_vβ₅ = 5.9 and α_vβ₈ = 7.7.

Borane-catalyzed metal-free hydrogenation of 2,7-disubstituted 1,8-naphthyridines

Metal-free hydrogenation of 2,7-disubstituted 1,8-naphthyridines was realized to furnish 1,2,3,4-tetrahydro-1,8-naphthyridines in high yields with up to 74% ee.

Asymmetric allylation of sulfonyl imines catalyzed by in situ generated Cu(ii) complexes of chiral amino alcohol based Schiff bases

We have developed a catalytic route for enantioselective synthesis of homoallyl amines through Cu(ii)-Schiff base catalyzed allylation of aryl N-sulfonylimines.

A general procedure for the preparation of beta-ketophosphonates

A mild, high-yielding procedure for the preparation of beta-ketophosphonates is described. The condensation is general with respect to the ester and phosphonate, and the products are obtained in high yields within minutes at 0 degrees C. The reaction procedure is operationally simple and amenable to large-scale preparations.

Concise route to the chiral pyrrolidine core of selective inhibitors of neuronal nitric oxide

2-(((3R,4R)-4-(Allyloxy)-1-benzylpyrrolidin-3-yl)methyl)-6-(2,5-dimethyl-1H-pyrrol-1-yl)-4-methylpyridine (2), a key intermediate for the preparation of novel neuronal nitric oxide synthase (nNOS) inhibitors, is synthesized using diisopropyl (R)-(+)-malate as the starting material. The key steps involve a Frater-Seebach diastereoselective alkylation and a fast intramolecular cyclization.

Aminolithiation of carbon-carbon double bonds as a powerful tool in organic synthesis

A conjugate amination of α,β-unsaturated carbonyl compounds with lithium amides has become a powerful method of N-C bond-forming reactions. Chiral ligand-controlled asymmetric version of the conjugate amination of enoates was developed for practical bench chemistry, giving the enantioenriched amination product with over 99 % ee. In situ diastereoselective alkylation of resulting lithium enolates allowed us to form vicinal N-C and C-C bonds in a one-pot operation. This protocol enabled us to realize a short-step asymmetric synthesis of otamixaban key intermediate. Treatment of product 3-benzylamino- and 3-allylaminoesters with tert-butyllithium gave five- or seven-membered lactams through [1,2]- or [2,3]-rearrangement of intermediate β-lactams. Isolated C-C double bonds were also found to accept intramolecular aminolithiation affording the corresponding hydroamination products. Chiral lithiophilic ligand-catalyzed reaction gave enantioenriched hydroamination products with high ee. Stereoselective intramolecular aminolithiation of allylaminoalkenes was coupled with subsequent carbolithiation to give doubly cyclized product amines.

Preparation of N-Alkylbis(3-aminopropyl)amines by the Catalytic Hydrogenation of N-Alkylbis(cyanoethyl)amines

An improved process for the preparation of N-alkylbis(3-aminopropyl)amines is described. These triamines are of interest as monomers for the condensation polymerization with esterified carbohydrate diacids (aldaric acids) to generate the corresponding poly(4-alkyl-4-azaheptamethylene aldaramides). The triamine synthesis is comprised of two efficient steps and requires no chromatographic purification. Bisconjugate addition of alkylamines to acrylonitrile followed by catalytic hydrogenation of the N-alkylbis(cyanoethyl)amines over Raney nickel yields the target N-alkylbis(3-aminopropyl)amines. Much less solvent was used in the bisconjugate addition step then previously reported, and in the second step, a relatively low-pressure catalytic hydrogenation (50 psi of hydrogen) was employed using Raney nickel as the catalyst in a 7 N methanolic ammonia solvent system to afford the N-alkylbis(3-aminopropyl)amines of high purity in nearly quantitative yield.

First total synthesis of louisianin A

The first total synthesis of louisianin A, 4-allyl-6,7-dihydro-1-hydroxycyclopenta[c]pyridin-5-one, is achieved from 2-chloro-4-cyanopyridine 5 via seven steps in an overall 24% yield. The key step is a cyclization-decarboxylation sequence toward the formation of a cyclopentenone ring.

Binding of Small Mono- and Oligomeric Integrin Ligands to Membrane-Embedded Integrins Monitored by Surface Plasmon-Enhanced Fluorescence Spectroscopy

We recently developed a binding assay format by incorporating native transmembrane receptors into artificial phospholipid bilayers on biosensor devices for surface plasmon resonance spectroscopy. By extending the method to surface plasmon-enhanced fluorescence spectroscopy (SPFS), sensitive recording of the association of even very small ligands is enabled. Herewith, we monitored binding of synthetic mono- and oligomeric RGD-based peptides and peptidomimetics to integrins alphavbeta3 and alphavbeta5, after having confirmed correct orientation and functionality of membrane-embedded integrins. We evaluated integrin binding of RGD multimers linked together via aminohexanoic acid (Ahx) spacers and showed that the dimer revealed higher binding activity than the tetramer, followed by the RGD monomers. The peptidomimetic was also found to be highly active with a slightly higher selectivity toward alphavbeta3. The different compounds were also evaluated in in vitro cell adhesion tests for their capacity to interfere with alphavbeta3-mediated cell attachment to vitronectin. We hereby demonstrated that the different RGD monomers were similarly effective; the RGD dimer and tetramer showed comparable IC50 values, which were, however, significantly higher than those of the monomers. Best cell detachment from vitronectin was achieved by the peptidomimetic. The novel SPFS-binding assay platform proves to be a suitable, reliable, and sensitive method to monitor the binding capacity of small ligands to native transmembrane receptors, here demonstrated for integrins.

Asymmetric Synthesis of Intermediates for Otamixaban and Premafloxacin by the Chiral Ligand-Controlled Asymmetric Conjugate Addition of a Lithium Amide

A chiral ligand-controlled conjugate addition reaction of lithium benzyl(trimethylsilyl)amide with tert-butyl enoates gave the corresponding lithium enolates that were then treated with electrophiles, giving anti-alkylation products with high ee up to 98%. The benzyl group on the amino nitrogen was removed by the oxidation of secondary amines to imines and subsequent transoximation to give 3-aminoalkanoates in good yields. The products are the possible key intermediates of otamixaban and premafloxacin.