Rhodium-Catalyzed Imination of Sulfoxides and Sulfides: Efficient Preparation of N-Unsubstituted Sulfoximines and Sulfilimines

The lab oddity prevails: discovery of pan-CDK inhibitor (R)-S-cyclopropyl-S-(4-{[4-{[(1R,2R)-2-hydroxy-1-methylpropyl]oxy}-5-(trifluoromethyl)pyrimidin-2-yl]amino}phenyl)sulfoximide (BAY 1000394) for the treatment of cancer

Lead optimization of a high-throughput screening hit led to the rapid identification of aminopyrimidine ZK 304709, a multitargeted CDK and VEGF-R inhibitor that displayed a promising preclinical profile. Nevertheless, ZK 304709 failed in phase I studies due to dose-limited absorption and high inter-patient variability, which was attributed to limited aqueous solubility and off-target activity against carbonic anhydrases. Further lead optimization efforts to address the off-target activity profile finally resulted in the introduction of a sulfoximine group, which is still a rather unusual approach in medicinal chemistry. However, the sulfoximine series of compounds quickly revealed very interesting properties, culminating in the identification of the nanomolar pan-CDK inhibitor BAY 1000394, which is currently being investigated in phase I clinical trials.

Investigating the mode of action of sulfoxaflor: a fourth-generation neonicotinoid

BACKGROUND

The precise mode of action of sulfoxaflor, a new nicotinic acetylcholine receptor-modulating insecticide, is unclear. A detailed understanding of the mode of action, especially in relation to the neonicotinoids, is essential for recommending effective pest management practices.

RESULTS

Radiolabel binding experiments using a tritiated analogue of sulfoxaflor ([(3) H]-methyl-SFX) performed on membranes from Myzus persicae demonstrate that sulfoxaflor interacts specifically with the high-affinity imidacloprid binding site present in a subpopulation of the total nAChR pool. In competition studies, imidacloprid-like neonicotinoids displace [(3) H]-methyl-SFX at pM concentrations. The effects of sulfoxaflor on the exposed aphid nervous system in situ are analogous to those of imidacloprid and nitenpyram, and finally the high-affinity sulfoxaflor binding site is absent in a Myzus persicae strain (clone FRC) possessing a single amino acid point mutation (R81T) in the β-nAChR, a region critical for neonicotinoid interaction.

CONCLUSION

The nicotinic acetylcholine receptor pharmacological profile of sulfoxaflor in aphids is consistent with that of imidacloprid. Additionally, the insecticidal activity of sulfoxaflor and the current commercialised neonicotinoids is affected by the point mutation in FRC Myzus persicae. Therefore, it is suggested that sulfoxalfor be considered a neonicotinoid, and that this be taken into account when recommending insecticide rotation partnering for effective resistance management programmes.

A sulfoximine-based inhibitor of human asparagine synthetase kills L-asparaginase-resistant leukemia cells

An adenylated sulfoximine transition-state analogue 1, which inhibits human asparagine synthetase (hASNS) with nanomolar potency, has been reported to suppress the proliferation of an l-asparagine amidohydrolase (ASNase)-resistant MOLT-4 leukemia cell line (MOLT-4R) when l-asparagine is depleted in the medium. We now report the synthesis and biological activity of two new sulfoximine analogues of 1 that have been studied as part of systematic efforts to identify compounds with improved cell permeability and/or metabolic stability. One of these new analogues, an amino sulfoximine 5 having no net charge at cellular pH, is a better hASNS inhibitor (K(I)(∗)=8 nM) than 1 and suppresses proliferation of MOLT-4R cells at 10-fold lower concentration (IC(50)=0.1mM). More importantly, and in contrast to the lead compound 1, the presence of sulfoximine 5 at concentrations above 0.25 mM causes the death of MOLT-4R cells even when ASNase is absent in the culture medium. The amino sulfoximine 5 exhibits different dose-response behavior when incubated with an ASNase-sensitive MOLT-4 cell line (MOLT-4S), supporting the hypothesis that sulfoximine 5 exerts its effect by inhibiting hASNS in the cell. Our work provides further evidence for the idea that hASNS represents a chemotherapeutic target for the treatment of leukemia, and perhaps other cancers, including those of the prostate.

Discovery and characterization of sulfoxaflor, a novel insecticide targeting sap-feeding pests

The discovery of sulfoxaflor [N-[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl]ethyl]-λ(4)-sulfanylidene] cyanamide] resulted from an investigation of the sulfoximine functional group as a novel bioactive scaffold for insecticidal activity and a subsequent extensive structure-activity relationship study. Sulfoxaflor, the first product from this new class (the sulfoximines) of insect control agents, exhibits broad-spectrum efficacy against many sap-feeding insect pests, including aphids, whiteflies, hoppers, and Lygus, with levels of activity that are comparable to those of other classes of insecticides targeting sap-feeding insects, including the neonicotinoids. However, no cross-resistance has been observed between sulfoxaflor and neonicotinoids such as imidacloprid, apparently the result of differences in susceptibility to oxidative metabolism. Available data are consistent with sulfoxaflor acting via the insect nicotinic receptor in a complex manner. These observations reflect the unique structure of the sulfoximines compared with neonicotinoids.

Intramolecular Fe(II)-catalyzed N-O or N-N bond formation from aryl azides

Iron(II) bromide catalyzes the transformation of aryl and vinyl azides with ketone or methyl oxime substituents into 2,1-benzisoxazoles, indazoles, or pyrazoles through the formation of an N-O or N-N bond. This transformation tolerates a variety of different functional groups to facilitate access to a range of benzisoxazoles or indazoles. The unreactivity of the Z-methyloxime indicates that N-heterocycle formation occurs through a nucleophilic attack of the ketone or oxime onto an activated planar iron azide complex.

The use of chiral lithium amides in the desymmetrisation of N-trialkylsilyl dimethyl sulfoximines

BACKGROUND

Chiral base desymmetrisation of dimethyl sulfoximines could provide a general route to chiral, enantioenriched dialkyl sulfoximines with potential for use in asymmetric catalysis.

RESULTS

Asymmetric deprotonation of N-trialkylsilyl dimethyl sulfoximines with either enantiomer of lithium N,N-bis(1-phenylethyl)amide in the presence of lithium chloride affords enantioenriched sulfoximines on electrophilic trapping. Ketones, ketimines, trialkylsilyl chlorides and activated alkyl halides may be used as electrophiles in the reaction. Furthermore, a modified Horner-Emmons methodology was investigated.

CONCLUSION

Simple chiral lithium amides afford products with enantiomeric excesses of up to 70%, illustrating that chiral base desymmetrisation of dimethyl sulfoximines is possible.

Iodinane- and Metal-Free Synthesis of N-Cyano Sulfilimines: Novel and Easy Access of NH-Sulfoximines

The synthesis of N-cyanosulfilimines can readily be achieved by reaction of the corresponding sulfides with cyanogen amine in the presence of a base and NBS or I2 as halogenating agents. Oxidation followed by C-N bond cleavage affords synthetically useful NH-free sulfoximines.

Comparative Study of Metal-Catalyzed Iminations of Sulfoxides and Sulfides

A comparative study of the imination of sulfur compounds with various metal catalysts in combination with isolated or in situ generated iminoiodinanes (PhI==NR) as nitrogen sources is presented. The influence of the metal catalyst towards the imination of a variety of substituted sulfoxides has been evaluated. Moreover, the effect of the different oxidation states of sulfur on the reactivity and selectivity of the nitrogen transfer redox process in the formation of sulfilimines and sulfoximines was studied. Depending on both the specific metal catalyst as well as the employed nitrene precursor, the sulfide/sulfoxide imination ratio varied in transformations of thianthrene-5-oxide and substituted para-thio phenylsulfoxides.

Synthesis ofN-(1H)-Tetrazole Sulfoximines

N-(1H)-Tetrazole sulfoximines are readily available by addition of sodium azide to the corresponding N-cyano derivatives in the presence of ZnBr2. The use of these N-(1H)-tetrazoles as intermediates in the synthesis of other N-heterocyclic sulfoximines is demonstrated.

Construction of Robust Ruthenium(salen)(CO) Complexes and Asymmetric Aziridination with Nitrene Precursors in the Form of Azide Compounds That Bear Easily RemovableN-Sulfonyl Groups

We synthesized new Ru(salen)(CO) complexes of high durability and achieved aziridination with good to excellent enantioselectivity by using azide compounds that contain an easily removable N-sulfonyl group, such as the 2-(trimethylsilyl)ethanesulfonyl group, as a nitrene precursor. Aziridination of less-reactive alpha,beta-unsaturated esters (and amides) proceeded with excellent enantioselectivities, from which it is inferred that an electrophilic species is the active species of this reaction. The present asymmetric aziridination provides a useful tool for introducing optically active nonprotected amine groups.

Iron-Catalyzed Imination of Sulfoxides and Sulfides

[reaction: see text] The Fe(III)-catalyzed imination of sulfoxides and sulfides with sulfonylamides in the presence of iodinanes has been investigated. The best results were obtained when Fe(acac)(3) was used as a catalyst in combination with iodosylbenzene, providing an effective alternative (stereospecific) access to sulfoximines and sulfilimines.

Silver-Catalyzed Imination of Sulfoxides and Sulfides

[reaction: see text] Silver salts in the presence of a chelating ligand efficiently catalyze the stereospecific imination of sulfoxides and sulfides with sulfonylamides and PhI(OAc)(2) to afford sulfoximines and sulfilimines, respectively, in good yields.

Asymmetric Decarboxylative Claisen Rearrangement Reactions of Sulfoximine-Substituted Allylic Tosylacetic Esters

Allylic acetate esters containing a variety of N-arylsulfonyl sulfoximines on the acetyl residue have been prepared and submitted to the decarboxylative Claisen rearrangement reaction. Rearranged products were isolated in generally good yields, and diastereoselectivities up to 82:18 have been obtained. The N-(2,4,6-triisopropylphenylsulfonyl)-S-phenyl sulfoximine moiety gave the best selectivity. The stereochemistry of the major isomer was established by X-ray crystallography. A model to explain the stereochemical course of the rearrangement is proposed.

Palladium-Catalyzed N-Vinylation of Sulfoximines

New previously unavailable N-vinyl sulfoximines have been synthesized by intermolecular palladium-catalyzed coupling between sulfoximines and vinyl bromides in excellent yield. Hydrogenation of the vinyl moiety opens a novel way to alpha-branched N-alkyl sulfoximines.

Efficient Copper-Mediated Reactions of Nitrenes Derived from Sulfonimidamides

[reaction: see text] Sulfonimidamides lead efficiently to nitrenes and have been converted to sulfimides, sulfoximines, and aziridines in good yields, through a copper-mediated multicomponent reaction. The stereogenic sulfur atom and the trivalent nitrogen atom present in the molecules open the way to asymmetric synthesis, whose first results are presented.