Identification and characterization of the first fragment hits for SETDB1 Tudor domain.

SET domain bifurcated protein 1 (SETDB1) is a human histone-lysine methyltransferase which is amplified in human cancers and was shown to be crucial in the growth of non-small and small cell lung carcinoma. In addition to its catalytic domain, SETDB1 harbors a unique tandem tudor domain which recognizes histone sequences containing both methylated and acetylated lysines, and likely contributes to its localization on chromatin. Using X-ray crystallography and NMR spectroscopy fragment screening approaches, we have identified the first small molecule fragment hits that bind to histone peptide binding groove of the Tandem Tudor Domain (TTD) of SETDB1. Herein, we describe the binding modes of these fragments and analogues and the biophysical characterization of key compounds. These confirmed small molecule fragments will inform the development of potent antagonists of SETDB1 interaction with histones.

A Study of Boratriazaroles: An Underdeveloped Class of Heterocycles.

Boratriazaroles were discovered in the late 1960s, and since then, a variety of substituted boratriazarole derivatives have been prepared. However, no study has compared the properties of these BN heterocycles with their carbon-based analogues. In this work, we have prepared a series of boratriazarole derivatives and have investigated how structural variations in the five-member heterocycle affect photophysical and electronic properties. Boratriazaroles exhibit absorption and emission spectra comparable to those of their azacycle analogues but have a markedly lower quantum yield. The quantum yield can be increased with the incorporation of a 2-pyridyl substitution on the boratriazaroles, and the structural and optoelectronic properties are further influenced by the nature of the B-aryl substituent. Introducing an electron-deficient p-cyano group on the B-phenyl substituent creates a twisted intramolecular charge transfer state that causes a large Stokes shift and positive solvatochromism. Our work should serve to guide future synthetic efforts toward the application of boratriazaroles in materials science.

Synthesis of Aminoboronic Acid Derivatives from Amines and Amphoteric Boryl Carbonyl Compounds.

Herein, we demonstrate the use of α-boryl aldehydes and acyl boronates in the synthesis of aminoboronic acid derivatives. This work highlights the untapped potential of boron-substituted iminium ions and offers insights into the behavior of N-methyliminodiacetyl (MIDA) boronates during condensation and tautomerization processes. The preparative value of this contribution lies in the demonstration that various amines, including linear and cyclic peptides, can be readily conjugated with boron-containing fragments. A mild deprotection of amino MIDA-boronates enables access to α- and ß-aminoboronic acids in high chemical yields. This simple process should be applicable to the synthesis of a wide range of bioactive molecules as well as precursors for cross-coupling reactions.

Stereocontrolled synthesis of 1,2- and 1,3-diamine building blocks from aziridine aldehyde dimers.

Vicinal aziridine-containing diamines have been obtained with high syn-stereoselectivity from readily available aziridine aldehyde dimers in the Petasis borono-Mannich reaction. Subsequent solvent- and/or nucleophile-dependent ring-opening of the aziridine ring yields functionalized 1,2- and 1,3-diamines with high regioselectivity. The ring opening is also influenced by the substitution at the C3 position of the aziridine. A mechanistic rationale for the highly syn-selective three-component reaction is proposed.

Synthesis and Mössbauer spectroscopy of formal tin(II) dichloride and dihydride species supported by Lewis acids and bases.

(119)Sn Mössbauer spectroscopy was performed on a series of formal Sn(II) dichloride and dihydride adducts bound by either carbon- or phosphorus-based electron pair donors. Upon binding electron-withdrawing metal pentacarbonyl units to the tin centers in LB·SnCl2·M(CO)5 (LB = Lewis base; M = Cr or W), a significant decrease in isomer shift (IS) was noted relative to the unbound Sn(II) complexes, LB·SnCl2, consistent with removal of nonbonding s-electron density from tin upon forming Sn-M linkages (M = Cr and W). Interestingly, when the nature of the Lewis base in the series LB·SnCl2·W(CO)5 was altered, very little change in the IS values was noted, implying that the LB-Sn bonds were constructed with tin-based orbitals of large p-character (as supported by prior theoretical studies). In addition, variable temperature Mössbauer measurements were used to determine the mean displacement of the tin atoms in the solid state, a parameter that can be correlated with the degree of covalent bonding involving tin in these species.

Expanding the steric coverage offered by bis(amidosilyl) chelates: isolation of low-coordinate N-heterocyclic germylene complexes.

The synthesis and coordination chemistry of a series of dianionic bis(amido)silyl and bis(amido)disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr(3)) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate N-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium(IV) dimers of the general form [LGe(µ-S)](2) (L = bis(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete Ge═S double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGe═S units to occur. Notably, the new triarylsilyl groups (4-RC(6)H(4))(3)Si- (R = (t)Bu and (i)Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, -SiPh(3,) and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry.

Stabilization of the heavy methylene analogues, GeH2 and SnH2, within the coordination sphere of a transition metal.

The heavy group 14 methylene analogues, EH2, (E = Ge and Sn) have been stabilized via efficient methods, thus enabling the chemistry of these novel inorganic hydrides to be explored in depth.

Author Correction: Amine hemilability enables boron to mechanistically resemble either hydride or proton.

During the revision of this Article prior to publication, a computational study was reported (Vallejos, M. M. & Pellegrinet, S. C. Theoretical study of the BF3-promoted rearrangement of oxiranyl N-methyliminodiacetic acid boronates. J. Org. Chem. 82, 5917-5925; 2017) that evaluates the nucleophilic boryl transfer mechanism predicted in this Article; this reference has now been added as number 19, and the subsequent references renumbered.

Amine hemilability enables boron to mechanistically resemble either hydride or proton.

Tetracoordinate MIDA (N-methyliminodiacetic acid) boronates have found broad utility in chemical synthesis. Here, we describe mechanistic insights into the migratory aptitude of the MIDA boryl group in boron transfer processes, and show that the hemilability of the nitrogen atom on the MIDA ligand enables boron to mechanistically resemble either a hydride or a proton. The first case involves a 1,2-boryl shift, in which boron migrates as a nucleophile in its tetracoordinate form. The second case involves a neighbouring atom-promoted 1,4-boryl shift, in which boron migrates as an electrophile in its pseudo-tricoordinate form. Density functional theory studies and in situ NMR measurements all suggest that MIDA can act as a dynamic switch. These findings encouraged the development of novel migration processes involving boron that exploit the chameleonic behaviour of boron by acting as both a nucleophile and an electrophile, including the first report of a compound with a boronate functionality bound to carbon in the carboxylic acid oxidation state.

Borylated oximes: versatile building blocks for organic synthesis.

Herein, we demonstrate the synthesis and functionalization of α-boryl aldoximes from α-boryl aldehydes, with no sign of C-to-N boryl migration. Selective modification of the oxime functionality enables access to a wide range of borylated compounds, such as borylated heterocycles and N-acetoxyamides. By reducing the α-boryl aldoximes, MIDA deprotection yields the corresponding ß-boryl hydroxylamines. As part of this study, we also demonstrate the utility of the boryl aldoxime motif in peptide conjugation.

A Linchpin Synthesis of 6-Hydroxyceramides from Aziridine Aldehydes.

A chemoselective N-oxidation/Meisenheimer rearrangement protocol was developed to generate vinylaziridine scaffolds from aziridine aldehydes. A subsequent Lewis acid-mediated aziridine ring opening with carboxylic acid nucleophiles followed by N-O bond cleavage furnishes a human skin 6-hydroxyceramide natural product in short order. The utility of this methodology is demonstrated by the preparation of a number of unnatural 6-hydroxyceramide analogues. This modular approach enables the expedient synthesis of poorly understood skin lipids, which may find application in therapeutics and cosmetics.

Condensation-Driven Assembly of Boron-Containing Bis(Heteroaryl) Motifs Using a Linchpin Approach.

Herein, we describe the bromomethyl acyl boronate linchpin--an enabling reagent for the condensation-driven assembly of novel bis(heteroaryl) motifs. This building block is readily accessible from commercially available starting materials. A variety of 2-amino- and 2-methylpyridines were reacted with MIDA-protected bromomethyl acylboronate to afford 2-boryl imidazo[1,2-a]pyridine and 2-boryl indolizine derivatives, respectively, in excellent yields. Subsequent condensation with hydroxyamidines and hydrazonamides converted the intermediate heterocycles into novel boron-containing bis(heteroaryl) units characterized by high thermal stability.

Intercepting low oxidation state main group hydrides with a nucleophilic N-heterocyclic olefin.

The N-heterocyclic olefin, IPr=CH(2) (IPr = [(HCNDipp)(2)C], Dipp = 2,6-(i)Pr(2)C(6)H(3)) has been demonstrated to be of sufficient Lewis basicity to stabilize main group hydrides in unusually low oxidation states.