Learning a Complete Image Indexing Pipeline

To work at scale, a complete image indexing system comprises two components: An inverted file index to restrict the actual search to only a subset that should contain most of the items relevant to the query; An approximate distance computation mechanism to rapidly scan these lists. While supervised deep learning has recently enabled improvements to the latter, the former continues to be based on unsupervised clustering in the literature. In this work, we propose a first system that learns both components within a unifying neural framework of structured binary encoding

Iridium-Catalyzed Asymmetric Hydrogenation of β,γ-Unsaturated γ‑Lactams: Scope and Mechanistic Studies

An efficient asymmetric hydrogenation of β,γ-unsaturated γ-lactams using an iridium–phosphoramidite complex is reported. The chiral γ-lactams were obtained in excellent yields and enantioselectivities (up to 99% yield and 99% ee). The mechanistic studies indicated that the reduced products were obtained via the hydrogenation of the <i>N</i>-acyliminium cations, generated from β,γ-unsaturated γ-lactams, which was verified by ¹H NMR analysis. The reaction was carried out at a reduced catalyst loading of 0.1 mol %, and the reduced products can be transformed to two potential bioactive compounds. A new route is provided for the synthesis of chiral γ-lactams

Synthesis of Chiral α,β-Unsaturated γ‑Amino Esters via Pd-Catalyzed Asymmetric Allylic Amination

A Pd-catalyzed asymmetric allylic amination of 4-substituted 2-acetoxybut-3-enoates with amines has been developed for the regiospecific synthesis of chiral α,β-unsaturated γ-amino esters. The desired chiral aminated products can be obtained in up to 98% yield, and 99% ee and can be conveniently transformed to chiral γ-amino acid/alcohol derivatives and chiral γ-lactams, which can then be subjected to the synthesis of several types of chiral drugs and drug candidates. The preferential formation of chiral γ-amino esters may be attributed to the bulky substituents on the right side of the allyl substrates. This work provides an efficient strategy for the synthesis of chiral α,β-unsaturated γ-amino esters and their derivatives

Synthesis of Chiral α,β-Unsaturated γ‑Amino Esters via Pd-Catalyzed Asymmetric Allylic Amination

A Pd-catalyzed asymmetric allylic amination of 4-substituted 2-acetoxybut-3-enoates with amines has been developed for the regiospecific synthesis of chiral α,β-unsaturated γ-amino esters. The desired chiral aminated products can be obtained in up to 98% yield, and 99% ee and can be conveniently transformed to chiral γ-amino acid/alcohol derivatives and chiral γ-lactams, which can then be subjected to the synthesis of several types of chiral drugs and drug candidates. The preferential formation of chiral γ-amino esters may be attributed to the bulky substituents on the right side of the allyl substrates. This work provides an efficient strategy for the synthesis of chiral α,β-unsaturated γ-amino esters and their derivatives

The Construction of Chiral Fused Azabicycles Using a Pd-Catalyzed Allylic Substitution Cascade and Asymmetric Desymmetrization Strategy

A highly enantioselective Pd-catalyzed asymmetric allylic substitution cascade of cyclic <i>N</i>-sulfonylimines with an accompanying asymmetric desymmetrization has been developed for the construction of fused tetrahydroindole derivatives bearing two chiral centers. Mechanistic studies confirmed that the cascade reaction proceeds by initial allylic alkylation and subsequent allylic amination. The first alkylation is a chirality-control step and represents an asymmetric desymmetrization of <i>cis</i>-cyclic allyl diacetates. The reaction has been performed on a gram scale, and the desired products can take part in several transformations

Additional file 1: of Hypoacetylation, hypomethylation, and dephosphorylation of H2B histones and excessive histone deacetylase activity in DU-145 prostate cancer cells

Materials and Methods [ 3 , 6 , 13 – 16 ]. (DOCX 26 kb

Synthesis and Structural Characterization of Nickel Complexes Possessing P‑Stereogenic Pincer Scaffolds and Their Application in Asymmetric Aza-Michael Reactions

Novel P-stereogenic pincer-Ni complexes {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Me^<i>t</i>BuPCH₂)₂C₆H}­NiCl (<b>3</b>), {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Me^<i>t</i>BuPCH₂)₂C₆H}­NiOTf (<b>4</b>), [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­NiCl]Cl (<b>7</b>), [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­NiCl]­BF₄ (<b>8</b>), and [{κ^P,κ^N,κ^P-2,6-(Me^<i>t</i>BuPCH₂)₂C₅H₃N}­Ni­(NCMe)]­(BF₄)₂ (<b>9</b>) were synthesized in 55–84% yields and characterized by ¹H NMR, ¹³C­{¹H} NMR, ³¹P­{¹H} NMR, ¹⁹F­{¹H} NMR, and/or single-crystal X-ray diffractions. The ORTEP diagrams of complexes <b>3</b>, <b>7</b>, <b>8</b>, and <b>9</b> show that the coordination geometries around the Ni center in all these structures are approximately square planar but have different bond lengths and angles. These complexes were shown to be active catalysts for the asymmetric aza-Michael addition of α,β<i>-</i>unsaturated nitriles. For most examples good to excellent yields (up to 99%) and moderate enantiomeric excesses (up to 46% ee) were obtained. Notably, the PCP complex <b>3</b> exhibited higher catalytic activity in the aza-Michael addition than the PNP complexes <b>7</b>, <b>8</b>, and <b>9</b>. Two achiral PCP-type pincer-Ni complexes, {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(^<i>t</i>Bu₂PCH₂)₂C₆H}­NiCl (<b>11</b>) and {κ^P,κ^C,κ^P-3,5-Me₂-2,6-(Ph₂PCH₂)₂C₆H}­NiCl (<b>13</b>), were also synthesized and fully characterized in order to reveal the structural differences between the chiral and achiral complexes

Asymmetric Hydrogenation of α‑Substituted Acrylic Acids Catalyzed by a Ruthenocenyl Phosphino-oxazoline–Ruthenium Complex

Asymmetric hydrogenation of various α-substituted acrylic acids was carried out using RuPHOX–Ru as a chiral catalyst under 5 bar H₂, affording the corresponding chiral α-substituted propanic acids in up to 99% yield and 99.9% ee. The reaction could be performed on a gram-scale with a relatively low catalyst loading (up to 5000 S/C), and the resulting product (97%, 99.3% ee) can be used as a key intermediate to construct bioactive chiral molecules. The asymmetric protocol was successfully applied to an asymmetric synthesis of dihydroartemisinic acid, a key intermediate required for the industrial synthesis of the antimalarial drug artemisinin