Asymmetric Syntheses of (−)-ADMJ and (+)-ADANJ: 2-Deoxy-2-amino Analogues of (−)-1-Deoxymannojirimycin and (+)-1-Deoxyallonojirimycin

Recent advances in the total synthesis of polyhydroxylated alkaloids via chiral oxazines

This review summarizes recently established methodologies developed for the enantioselective and diastereoselective synthesis of chiral 1,3-oxazines. These compounds are of interest as advanced synthetic intermediates in the total synthesis of structurally complex and biologically active polyhydroxylated alkaloids such as (+)-1-deoxynojirimycin, (-)-anisomycin, (+)-castanospermine, (+)-casuarine, (-)-conduramine F-1, (-)-sphingofungin B, Neu5Ac methyl ester, and other natural products. The devised synthetic approach aims to offer a direct, efficient, and adaptable method for obtaining both pure enantiomers and pure diastereomers. It revolves around utilizing chiral building blocks like syn,syn-, syn,syn,anti-, syn,anti-, syn,anti,syn-, anti,syn-, anti,syn,syn-, and anti,syn,anti-oxazines. By integrating oxazine chemistry with established and innovative transformations, this approach enabled the synthesis of 30 polyhydroxylated amines across various studies conducted between 2007 and 2022.

Isoform selectivities of novel 4-hydroxycoumarin imines as inhibitors of myosin II

Muscle myosin inhibition could be used to treat many medical conditions involving hypercontractile states, including muscle spasticity, chronic musculoskeletal pain, and hypertrophic cardiomyopathy. A series of 13 advanced analogs of 3-(N-butylethanimidoyl)ethyl)-4-hydroxy-2H-chromen-2-one (BHC) were synthesized to explore extended imine nitrogen side chains and compare aldimines vs. ketimines. None of the new analogs inhibit nonmuscle myosin in a cytokinesis assay. ATPase structure-activity relationships reveal that selectivity for cardiac vs. skeletal myosin can be tuned with subtle structural changes. None of the compounds inhibited smooth muscle myosin II. Docking the compounds to homology models of cardiac and skeletal myosin II gave rationales for the effects of side arm length on inhibition selectivity and for cardiac vs. skeletal myosin. Properties including solubility, stability and toxicity, suggest that certain BHC analogs may be useful as candidates for preclinical studies or as lead compounds for advanced candidates for drugs with cardiac or skeletal muscle myosin selectivity.

Structure-activity relationship studies on the inhibition of the bacterial translation of novel Odilorhabdins analogues

A structure-activity relationship (SAR) study of NOSO-95179, a nonapeptide from the Odilorhabdin class of antibacterials, was performed by systematic variations of amino acids in positions 2 and 5 of the peptide. A series of non-proteinogenic amino acids was synthesized in high enantiomeric purity from Williams' chiral diphenyloxazinone by highly diastereoselective alkylation or by aldol-type reaction. NOSO-95179 analogues for SAR studies were prepared using solid-phase peptide synthesis. Inhibition of bacterial translation by each of the synthesized Odilorhabdin analogues was measured using an in vitro test. For the most efficient analogues, antibacterial efficacy was measured against two wild-type Enterobacteriaceae (Escherichia coli and Klebsiella pneumoniae) and against an efflux defective E. coli strain (ΔtolC) to evaluate the impact of efflux on the antibacterial activity.

Homoallylic amines as efficient chiral inducing frameworks in the conjugate addition of amides to α,β-unsaturated esters. An entry to enantio-enriched diversely substituted amines

The diastereoselective conjugate addition of secondary homoallylamines, obtained in the enantioenriched form via allylmetallation of imines, to α,β-unsaturated esters is reported. This method allows access to valuable building blocks as well as heterocyclic skeletons, providing tertiary amines bearing two chains integrating a stereogenic center adjacent to the nitrogen atom.

H-bonding vs Protonation of Alkynes in Regioselective Hydroamination Reactions: A Glimpse into the Reactivity of Arylogous Ynolethers and Ynamines

In this paper is described the competition and transition between hydrogen bonding and protonation of alkynes connected, on one side, to various aromatic rings and to chiral amino ester appendages on the other side. While the first mode of activation induced the cyclization into pyrrolidines, the protonation of the alkyne led preferentially to tetrahydropyridines due to the higher level of the highest occupied molecular orbital (HOMO) of the considered arylogous ynolethers and ynamines. The transition between H-bonding and protonation was observed with the alkyne substituted with 2-methoxyphenyl, for which the cyclization delivered either five- or six-membered rings depending on the temperature of the experiment. From there, the cyclization of dialkoxy- and trialkoxyphenyl-substituted alkynes into six-membered rings, i.e., tetrahydropyridines, was developed. When next applied to alkynylindoles, the same pattern of cyclization provided six-membered rings as an illustration of the reactivity of arylogous ynamines. Thanks to the high reactivity of the intermediate cationic species, weak nucleophiles such as NH-oxazolidinone participated efficiently in the hydroamination reaction of alkynylindoles. Pyrrolidines, tetrahydropyridines, and piperidines decorated with various aromatics and substituents were thus prepared in enantio- and stereoselective manner. Capitalizing on the enamine moiety of the azaheterocycles, the molecular diversity was extended through stereoselective oxidation and ring contraction processes.

Rhodium(III)-Catalyzed Directed C-H Dienylation of Anilides with Allenes Leads to Highly Conjugated Systems

Allenes are unique coupling partners in transition-metal-catalyzed C-H functionalization leading to a variety of products via alkenylation, allenylation, allylation, and annulation reactions. The outcome is governed by both the reactivity of the allene and the formation and stability of the organometallic intermediate. An efficient Rh(III)-catalyzed, weakly coordinating group-directed dienylation of electronically unbiased allenes is developed using an N-acyl amino acid as a ligand. Further elaboration of the dienylated products to construct polycyclic compounds is also described.

Amino-functionalized iminocyclitols: synthetic glycomimetics of medicinal interest

A review on the syntheses and biological activities of unnatural glycomimetics highlighting the effect of replacement of hydroxyl groups of natural iminosugars by amino functionalities is presented.