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Transition metal-catalyzed asymmetric nitrene transfer is a powerful method to generate enantioenriched amines found in natural products and bioactive molecules.

 

NAKED ENDOSPERM1 (NKD1), NKD2, and OPAQUE2 (O2) are transcription factors important for cell patterning and nutrient storage in maize (Zea mays) endosperm. To study the complex regulatory interrelationships among these 3 factors in coregulating gene networks, we developed a set of nkd1, nkd2, and o2 homozygous lines, including all combinations of mutant and wild-type genes. Among the 8 genotypes tested, we observed diverse phenotypes and gene interactions affecting cell patterning, starch content, and storage proteins. From ∼8 to ∼16 d after pollination, maize endosperm undergoes a transition from cellular development to nutrient accumulation for grain filling. Gene network analysis showed that NKD1, NKD2, and O2 dynamically regulate a hierarchical gene network during this period, directing cellular development early and then transitioning to constrain cellular development while promoting the biosynthesis and storage of starch, proteins, and lipids. Genetic interactions regulating this network are also dynamic. The assay for transposase-accessible chromatin using sequencing (ATAC-seq) showed that O2 influences the global regulatory landscape, decreasing NKD1 and NKD2 target site accessibility, while NKD1 and NKD2 increase O2 target site accessibility. In summary, interactions of NKD1, NKD2, and O2 dynamically affect the hierarchical gene network and regulatory landscape during the transition from cellular development to grain filling in maize endosperm.

 

We report a highly enantioselective intermolecular C−H bond silylation catalyzed by a phosphoramidite‐ligated iridium catalyst. Under reagent‐controlled protocols, propargylsilanes resulting from C(sp³)−H functionalization, as well the regioisomeric and synthetically versatile allenylsilanes, could be obtained with excellent levels of enantioselectivity and good to excellent control of propargyl/allenyl selectivity. In the case of unsymmetrical dialkyl acetylenes, good to excellent selectivity for functionalization at the less‐hindered site was also observed. A variety of electrophilic silyl sources (R₃SiOTf and R₃SiNTf₂), either commercial or in situ‐generated, were used as the silylation reagents, and a broad range of simple and functionalized alkynes, including aryl alkyl acetylenes, dialkyl acetylenes, 1,3‐enynes, and drug derivatives were successfully employed as substrates. Detailed mechanistic experiments and DFT calculations suggest that an η³‐propargyl/allenyl Ir intermediate is generated upon π‐complexation‐assisted deprotonation and undergoes outer‐sphere attack by the electrophilic silylating reagent to give propargylic silanes, with the latter step identified as the enantiodetermining step.

 

We report a highly enantioselective intermolecular C−H bond silylation catalyzed by a phosphoramidite‐ligated iridium catalyst. Under reagent‐controlled protocols, propargylsilanes resulting from C(sp³)−H functionalization, as well the regioisomeric and synthetically versatile allenylsilanes, could be obtained with excellent levels of enantioselectivity and good to excellent control of propargyl/allenyl selectivity. In the case of unsymmetrical dialkyl acetylenes, good to excellent selectivity for functionalization at the less‐hindered site was also observed. A variety of electrophilic silyl sources (R₃SiOTf and R₃SiNTf₂), either commercial or in situ‐generated, were used as the silylation reagents, and a broad range of simple and functionalized alkynes, including aryl alkyl acetylenes, dialkyl acetylenes, 1,3‐enynes, and drug derivatives were successfully employed as substrates. Detailed mechanistic experiments and DFT calculations suggest that an η³‐propargyl/allenyl Ir intermediate is generated upon π‐complexation‐assisted deprotonation and undergoes outer‐sphere attack by the electrophilic silylating reagent to give propargylic silanes, with the latter step identified as the enantiodetermining step.

 

In recent years, deep learning gained proliferating popularity in the cybersecurity application domain, since when being compared to traditional machine learning methods, it usually involves less human efforts, produces better results, and provides better generalizability. However, the imbalanced data issue is very common in cybersecurity, which can substantially deteriorate the performance of the deep learning models. This paper introduces a transfer learning based method to tackle the imbalanced data issue in cybersecurity using return-oriented programming payload detection as a case study. We achieved 0.0290 average false positive rate, 0.9705 average F1 score and 0.9521 average detection rate on 3 different target domain programs using 2 different source domain programs, with 0 benign training data sample in the target domain. The performance improvement compared to the baseline is a trade-off between false positive rate and detection rate. Using our approach, the total number of false positives is reduced by 23.16%, and as a trade-off, the number of detected malicious samples decreases by 0.68%.

 

Within the life cycle of a living organism, another life cycle exists for the selfish genome inhabitants, which are called transposable elements (TEs). These mobile sequences invade, duplicate, amplify, and diversify within a genome, increasing the genome's size and generating new mutations. Cells act to defend their genome, but rather than permanently destroying TEs, they use chromatin-level repression and epigenetic inheritance to silence TE activity. This level of silencing is ephemeral and reversible, leading to a dynamic equilibrium between TE suppression and reactivation within a host genome. The coexistence of the TE and host genome can also lead to the domestication of the TE to serve in host genome evolution and function. In this review, we describe the life cycle of a TE, with emphasis on how epigenetic regulation is harnessed to control TEs for host genome stability and innovation. 

We developed intramolecular carboxyamidations of alkyne‐tetheredO‐acylhydroxamates followed by either thermally induced spontaneous or 4‐(dimethylamino)pyridine‐catalyzed O→O or O→N acyl group migration. Under iron‐catalyzed conditions, the carboxyamidation products were generated in high yield from bothZ‐alkene and arene‐tethered substrates. DFT calculations indicate that the iron‐catalyzed carboxyamidation proceeds via a stepwise mechanism involving iron‐imidyl radical cyclization followed by intramolecular acyloxy transfer from the iron center to the alkenyl radical center to furnish thecis‐carboxyamidation product. Upon treatment with 4‐(dimethylamino)pyridine, theZ‐alkene‐tethered carboxyamidation products underwent selective O→O acyl migration to generate 2‐acyloxy‐5‐acyl pyrroles. Thermal O→N acyl migration occurs during carboxyamidation if theZ‐alkene linker contains an alkyl or an aryl substituent at the β‐position of the carbonyl group. On the other hand, the arene linker‐containing compounds selectively undergo O→N acyl migration to generateN‐acyl‐3‐acylisoindolinones, and the corresponding O→O acyl migration forming isoindole derivatives was not observed.