Asymmetric Synthesis of a Potent CXCR7 Modulator Featuring a Hindered Tertiary β-Amino Amide Stereocenter

A practical and asymmetric synthesis of a small-molecule CXCR7 modulator featuring a highly functionalized and hindered tertiary β-amino amide framework is reported. The cornerstone of this strategy relied on the intermediacy of a reactive aziridinium species, which, following regioselective ring opening with cyanide, furnished the desired chiral β-tertiary amino nitrile for further elaboration. As a means of further highlighting this synthetic strategy, an expanded scope of hindered β-amino amide synthesis is also presented.

Discovery of P2X3 selective antagonists for the treatment of chronic pain

Purinergic receptor P2X3 has been linked to analgesia in a number of pre-clinical models of pain, and is expressed in the human pain perception pathway. Only few P2X3-selective antagonists have been reported to date. This Letter describes the SAR and in vivo analgesic profile of a novel scaffold of selective P2X3 antagonists.

Phenolic P2/P3 core motif as thrombin inhibitors—Design, synthesis, and X-ray co-crystal structure

Prototypical thrombin inhibitors were synthesized based on a trisubstituted phenol as a core motif. A naphthylsulfonamide analogue showed excellent antithrombin activity. An X-ray co-crystal structure showed the expected interactions.

Structure-based design, synthesis, and memapsin 2 (BACE) inhibitory activity of carbocyclic and heterocyclic peptidomimetics

Molecular modeling based on the X-ray crystal structure of the Tang-Ghosh heptapeptide inhibitor 1 (OM99-2) of BACE led to the design and synthesis of a series of constrained P(1)' analogues. A cyclopentane ring was incorporated in 1 spanning the P(1)' Ala methyl group and the adjacent methylene carbon atom of the chain. Progressive truncation at the P(2)'-P(4)' sites led to a potent truncated analogue 5 with good selectivity over Cathepsin D. Using the same backbone replacement concept, a series of cyclopentane, cyclopentanone, tetrahydrofuran, pyrrolidine, and pyrrolidinone analogues were synthesized with considerable variation at the P and P' sites. The cyclopentanone and 2-pyrrolidinone analogues 45 and 57 showed low nM BACE inhibition. X-ray cocrystal structures of two analogues 5 and 45 revealed excellent convergence with the original inhibitor 1 structure while providing new insights into other interactions which could be exploited for future modifications.

Structure-Based Design, Synthesis, and Memapsin 2 (BACE) Inhibitory Activity of Carbocyclic and Heterocyclic Peptidomimetics

Molecular modeling based on the X-ray crystal structure of the Tang-Ghosh heptapeptide inhibitor 1 (OM99-2) of BACE led to the design and synthesis of a series of constrained P(1)' analogues. A cyclopentane ring was incorporated in 1 spanning the P(1)' Ala methyl group and the adjacent methylene carbon atom of the chain. Progressive truncation at the P(2)'-P(4)' sites led to a potent truncated analogue 5 with good selectivity over Cathepsin D. Using the same backbone replacement concept, a series of cyclopentane, cyclopentanone, tetrahydrofuran, pyrrolidine, and pyrrolidinone analogues were synthesized with considerable variation at the P and P' sites. The cyclopentanone and 2-pyrrolidinone analogues 45 and 57 showed low nM BACE inhibition. X-ray cocrystal structures of two analogues 5 and 45 revealed excellent convergence with the original inhibitor 1 structure while providing new insights into other interactions which could be exploited for future modifications.

Stereoselective Synthesis of Constrained Oxacyclic Hydroxyethylene Isosteres of Aspartic Protease Inhibitors: Aldol and Mukaiyama Aldol Methodologies for Branched Tetrahydrofuran 2-Carboxylic Acids

The synthesis of diastereomeric 3-substituted-tetrahydrofuran 2-carboxylic acids in enantiopure form was achieved relying on aldol condensations of N-substituted alpha-amino aldehydes with enolates and enol silyl ethers of gamma-butyrolactone. Catalytic YbFOD leads to a high yield of a syn/syn-alpha-amino alcohol isomer. This was used as a constrained THF subunit in the synthesis of a peptidomimetic intended as an inhibitor of the enzyme BACE1, which is implicated in the cascade of events leading to plaque formation in Alzheimer's disease.

Design and synthesis of a novel class of constrained tricyclic pyrrolizidinone carboxylic acids as carbapenem mimics

A series of tricyclic pyrrolizidinone carboxylic acids harboring an angular methano group were synthesized as mimics of carbapenems and carbapenams. A key reaction involved a novel intramolecular cyclopropanation mediated by a trimethylstannylmethyl group and an adjacent iminium ion. Enolate chemistry on a tricyclic lactam ring unit allowed the introduction of various substituents. Further elaboration afforded tricyclic pyrrolidinone carboxylic acids, which were found to be inactive as inhibitors against a panel of bacterial strains. However, the antibacterial activity of ceftazidine was enhanced in the presence of the tricyclic analogues.

Total synthesis of A-315675: a potent inhibitor of influenza neuraminidase

A concise, stereocontrolled, and practical synthesis of a neuraminidase inhibitor consisting of a highly functionalized D-proline scaffold is described. Key features involve a stereocontrolled addition of a propiolate ester to a chiral nonracemic nitrone derived originally from D-serine and the manipulation of acyclic and cyclic motifs en route to the target in 12.8% overall yield over 22 steps. Several crystalline intermediates were suitable for single-crystal X-ray analysis.

Pyrrolidine as a cogwheel-like scaffold for the deployment of diverse functionality through cycloaddition reactions of metallo-1,3-dipoles in aqueous media

The reaction of glycinatocopper complexes with cinnamaldehydes under mildy basic aqueous conditions, affords polysubstituted prolines, which can be systematically modified in a number of chemoselective transformations.

Absorption spectroscopy of (Ind)Ni(PPh3)X (Ind = indenyl, 1-Me-indenyl; X = Cl, Br, Me) and M(Ind)2 (M = Ni, Ru; Ind = indenyl)

The electronic structures of two types of transition metal indenyl complexes have been studied. The first type, a series of (Ind)Ni(PPh3)X compounds (Ind = indenyl, 1-Me-indenyl; X = Cl, Br, Me) was investigated by absorption spectroscopy and Extended Hückel Molecular Orbital calculations. The energy differences between calculated levels are in good agreement with experimental band positions. For example, the lowest energy singlet–singlet band maximum for (Ind)Ni(PPh3)Cl is at 19 500 cm−1 and the calculated HOMO–LUMO difference is 19 817 cm−1. For X = Me, the calculated energy difference increases to 21 930 cm−1 and the corresponding absorption band is at 22 500 cm−1. The influence of the metal–ligand interactions on the molecular orbitals is discussed. The second category of indenyls, the bis(indenyl) compounds of Ni and Ru, show absorption spectra that are markedly different from those of nickelocene and ruthenocene. For example, in comparison to nickelocene, the first absorption band of Ni(Ind)2 is 5700 cm−1 higher in energy and is more intense by two orders of magnitude; in contrast, the first absorption maximum of Ru(Ind)2 is 6600 cm−1 lower in energy than observed for ruthenocene. The characteristics and relaxation dynamics of the lowest energy excited states are discussed. Key words: absorption spectroscopy, indenyl, nickel, ruthenium, EHMO analysis.