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Novel indolizines and pyrrolo[1,2-c]pyrimidines bearing a 3-carbonylchromen-2-one moiety on the pyrrole rings were synthesized and spectroscopic properties of some of synthesized compounds were investigated. Synthetic procedures started from 4-substituted pyrimidines, 3-(2-bromoacetyl)-2H-chromen-2-one and electron-deficient alkynes via 3+2 dipolar cycloaddition of cycloimmonium-ylides, generated in situ from their corresponding quaternary salts, in the presence of an epoxide playing the role of acid scavenger and reaction solvent. The structures of novel compounds were confirmed by chemical analyses, IR and NMR spectroscopy. Spectroscopic properties of some of the synthesized compounds were investigated.

El pdf del artículo es el manuscrito de autor (PMCID:PMC2813333). ; NovP is an S-adenosyl-l-methionine-dependent O-methyltransferase that catalyzes the penultimate step in the biosynthesis of the aminocoumarin antibiotic novobiocin. Specifically, it methylates at 4-OH of the noviose moiety, and the resultant methoxy group is important for the potency of the mature antibiotic: previous crystallographic studies have shown that this group interacts directly with the target enzyme DNA gyrase, which is a validated drug target. We have determined the high-resolution crystal structure of NovP from Streptomyces spheroides as a binary complex with its desmethylated cosubstrate S-adenosyl-l-homocysteine. The structure displays a typical class I methyltransferase fold, in addition to motifs that are consistent with a divalent-metal-dependent mechanism. This is the first representative structure of a methyltransferase from the TylF superfamily, which includes a number of enzymes implicated in the biosynthesis of antibiotics and other therapeutics. The NovP structure reveals a number of distinctive structural features that, based on sequence conservation, are likely to be characteristic of the superfamily. These include a helical 'lid' region that gates access to the cosubstrate binding pocket and an active center that contains a 3-Asp putative metal binding site. A further conserved Asp likely acts as the general base that initiates the reaction by deprotonating the 4-OH group of the noviose unit. Using in silico docking, we have generated models of the enzyme–substrate complex that are consistent with the proposed mechanism. Furthermore, these models suggest that NovP is unlikely to tolerate significant modifications at the noviose moiety, but could show increasing substrate promiscuity as a function of the distance of the modification from the methylation site. These observations could inform future attempts to utilize NovP for methylating a range of glycosylated compounds. ; I.G.G., C.E.M.S., and D.M.L. were supported by the Biotechnology and Biological Sciences Research Council through responsive mode funding (ref. B19400) and by a Core Strategic Grant to the John Innes Center. I.U. was supported by the European Union Integrated Project BIOXHIT and the Spanish MEC (grant BIO2006-14139). C.L.F.M. and C.T.W. were supported by National Institutes of Health grants F32 AI054007 and GM 20011, respectively. ; Peer reviewed

We have performed a systematic study on the crystal structures and electronic properties of two ternary hydrides, YSH6 and LaSH6, under pressure, using the particle swarm optimization method and first-principles calculations. As a result of extensive structure searches, metallic YSH6 and LaSH6 are thermodynamically stable between 195-237 and 170-300 GPa, respectively. Interestingly, in YSH6 eight neighboring hydrogen atoms form octagons, and the octagons in different layers are connected by four sulfur atoms, forming a cagelike structure with a Y atom at the center, while those octagons in the same layer form polyphenylene-like chains via one shared side. In LaSH6, however, hydrogen atoms form both curved >H5> chains or straight chains when bonded to sulfur atoms. Furthermore, electron-phonon coupling calculations indicate that YSH6 and LaSH6 are promising superconductors with estimated Tc values of 91 and 35 K at 210 and 300 GPa, respectively. These results provide guidance for future experimental studies and stimulate more exploration on ternary hydrides. ; The work was supported by the National Natural Science Foundation of China (Grants No. 11604290 and No. 51732010), National Key R & D Program of China (Grant No. 2018YFA0703400), Funding Program for Recruited Oversea Scholars of Hebei Province (Grant No. CL201729), the Ph.D. Foundation by Yanshan University (Grant No. B970), and the Natural Science Research Project of Education Department of Anhui Province (KJ2018A0342). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P) and the Department of Education, Universities and Research of the Basque Government and the University of the Basque Country (IT756-13).

We have performed a systematic study on the crystal structures and electronic properties of two ternary hydrides, YSH6 and LaSH6, under pressure, using the particle swarm optimization method and first-principles calculations. As a result of extensive structure searches, metallic YSH6 and LaSH6 are thermodynamically stable between 195-237 and 170-300 GPa, respectively. Interestingly, in YSH6 eight neighboring hydrogen atoms form octagons, and the octagons in different layers are connected by four sulfur atoms, forming a cagelike structure with a Y atom at the center, while those octagons in the same layer form polyphenylene-like chains via one shared side. In LaSH6, however, hydrogen atoms form both curved >H5> chains or straight chains when bonded to sulfur atoms. Furthermore, electron-phonon coupling calculations indicate that YSH6 and LaSH6 are promising superconductors with estimated Tc values of 91 and 35 K at 210 and 300 GPa, respectively. These results provide guidance for future experimental studies and stimulate more exploration on ternary hydrides. ; The work was supported by the National Natural Science Foundation of China (Grants No. 11604290 and No. 51732010), National Key R & D Program of China (Grant No. 2018YFA0703400), Funding Program for Recruited Oversea Scholars of Hebei Province (Grant No. CL201729), the Ph.D. Foundation by Yanshan University (Grant No. B970), and the Natural Science Research Project of Education Department of Anhui Province (KJ2018A0342). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P) and the Department of Education, Universities and Research of the Basque Government and the University of the Basque Country (IT756-13).

The title compound (1), C19H20N2O2, crystallized with single molecule in the asymmetric unit and is present in the zwitterionic form. The compound was synthesized from the condensation reaction of 8-hydroxyjulolidine-9-carbaldehyde and 3-aminophenol. In solid state compound adopts the keto–amine tautomeric form, with the H atom attached to the N atom, which participates in an intramolecular N—H···O hydrogen bond with an S(6) ring motif. The conformation about the C=N bond is E. The aromatic ring of the julolidine moiety is inclined to the phenol ring by 13.00 (10)°. The fused non-aromatic rings of the julolidine moiety adopts a screw-boat conformations. In the crystal, the molecules are connected by N—H···O and O—H···O hydrogen bonds, with adjacent molecules related by a 21 screw axis, generating– A–B–A–B–zigzag chains extending along [010]. Furthermore, adjacent molecules are linked by pairs of C—H···O interactions, forming a ladder-like structure propagating along the a-axis direction. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level is compared with the experimentally determined molecular structure in the solid state.

Medium-resolution cryo-electron microscopy maps, in particular when they include a significant number of α-helices, may allow the building of partial models that are useful for molecular-replacement searches in large crystallo­graphic structures when the structures of homologs are not available and experimental phasing has failed. Here, as an example, the solution of the structure of a bacteriophage portal using a partial 30% model built into a 7.8 Å resolution cryo-EM map is shown. Inspection of the self-rotation function allowed the correct oligomerization state to be determined, and density-modification procedures using rotation matrices and a mask based on the cryo-EM structure were critical for solving the structure. A workflow is described that may be applicable to similar cases and this strategy is compared with direct use of the cryo-EM map for molecular replacement. ; The following funding is acknowledged: Ministry of Science, Innovation and Universities of Spain (grant Nos. BFU2014-53550-P and BFU2017-83720-P to Miquel Coll; grant No. BFU2014-54181 to Jose´ L. Carrascosa; contract No. SEV2013-0347 to Ana Cuervo; contract No. RYC-2011-09071 to Cristina Machon; award No. SEV-2015-0500 to IRB Barcelona; award No. MDM-2014-0435 to IBMB Structural Biology Unit); Catalan Government CERCA Programme (grant to IRB Barcelona).

Lattice partitions of a plane into polyominoes were constructed for N from 3 to 12, where N is the order of the packing space. We obtained 5191 symmetric independent lattice partitions of a plane with one polyomino in a reduced (primitive) cell, among which 122 variants belong to the structural class cm, Z = 2(m), with the elementary conventional cell being rectangular (centered). Chain partitions of planes have been derived, for which both structural class and structural subclass were identified. The results of the analysis of lattice partitions of a plane into polyominoes were illustrated with examples of real molecular layers in crystal structures.