Yan-Guang Wang

Bio: Yan-Guang Wang is an academic researcher from Zhejiang University. The author has contributed to research in topics: Hydrogen bond & Absolute configuration. The author has an hindex of 2, co-authored 6 publications receiving 6 citations.

(5aR,8aR,9R)-9-(3,4,5-Tri­methoxy­phenyl)-5a,6,8a,9-tetra­hydro­furo­[3′,4′:6,7]­naphtho­[2,3-d][1,3]­dioxole-5,8-dione

Abstract: The title compound, C22H20O8, a product of oxidation of podophyl­lotoxin, a lignan of the phenyl­tetralin type, represents a synthon for potential antitumour agents It has the same configuration of three chiral centres as the starting material, podophyl­lotoxin, and, as well as the latter, contains a γ-lactone ring trans-fused to the tricylic system Non-classical C—H⋯O hydrogen bonds link the mol­ecules in the crystal structure into infinite chains along the a axis

3-[(2R*,3S*)-3-(4-Chlorophenyl)-3-(2-methoxyanilino)-2-methylpropionyl]spiro[2H-1,3-benzoxazine-2,1′-cyclohexan]-4(3H)-one

Abstract: The title compound, C30H31ClN2O4, crystallizes as discrete mol­ecules Non-classical C—H·O hydrogen bonds link the mol­ecules in the crystal structure into a sheet parallel to (01)

4‐(9‐Acridin‐9‐yl­amino)‐2,2,6,6‐tetra­methyl­piperidine N‐oxide

Abstract: The title compound, C22H26N3O, crystallizes in space group P21 with two mol­ecules in the asymmetric unit. Intermolecular N—H⋯O hydrogen bonds play an important role in the formation of polymeric chains running along the crystallographic a axis.

3‐[(2R*,3S*)‐3‐(2‐Methoxy­anilino)‐2‐methyl‐3‐phenyl­propionyl]­spiro­[2H‐1,3‐benzoxazine‐2,1′‐cyclo­hexan]‐4(3H)‐one

Abstract: The racemic title compound, C30H32N2O4, was synthesized from spiro­[2H-1,3-benzoxazine-2,1′-cyclo­hexan]-4(3H)-one and N-benzyl­idene-2-methoxy­benzen­amine under classical Reformatsky reaction conditions. Intermolecular N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules in the crystal structure into infinite chains along the a axis. These chains form layers parallel to the (001) plane, which are stabilized by weak interlayer C—H⋯O hydrogen bonds.

(5α,8α,9β,11S)‐5,7,8,9‐Tetra­hydro‐11‐(fluoro­meth­yl)‐9‐(3,4,5‐trimethoxy­phen­yl)‐5,8‐methano‐1,3‐dioxolo[4,5‐h][2]benzoxepin

Abstract: The title compound, C22H23FO6, is an unexpected product of the fluorination of podophyllol. The absolute configuration was determined from the known configuration of the synthetic precursor. Non-classical C—H⋯O hydrogen bonds link the mol­ecules in the crystal structure into sheets parallel to (001).

On the Use of Least-Squares Restraints for Origin Fixing in Polar Space Groups

Abstract: The theory of fixing the origin of the coordinate system in a polar space group by use of restraints (soft constraints or pseudo-observations) is developed for any space group in any setting. The coefficients of the optimal restraint equation are on the average proportional to the square of the atomic numbers. They are determined directly from the unrestrained singular normal-equations matrix. Application of the restraint results in a positive-definite matrix which is as nearly diagonal as possible for the atomic positional coordinates along the origin-free axes. Correlations between these coordinates are therefore minimized. A very compact completely general and easily implemented algorithm results which functions without user intervention.

Acyclic Twisted Amides.

Abstract: In this contribution, we provide a comprehensive overview of acyclic twisted amides, covering the literature since 1993 (the year of the first recognized report on acyclic twisted amides) through June 2020. The review focuses on classes of acyclic twisted amides and their key structural properties, such as amide bond twist and nitrogen pyramidalization, which are primarily responsible for disrupting nN to π*C═O conjugation. Through discussing acyclic twisted amides in comparison with the classic bridged lactams and conformationally restricted cyclic fused amides, the reader is provided with an overview of amidic distortion that results in novel conformational features of acyclic amides that can be exploited in various fields of chemistry ranging from organic synthesis and polymers to biochemistry and structural chemistry and the current position of acyclic twisted amides in modern chemistry.

Unusual Magnetic Behavior of a 2D Citrate‐Bridged Dysprosium(III) Coordination Polymer

Abstract: A new lanthanide citrate coordination polymer [Dy(citrate)(H2O)]n (1) was hydrothermally synthesized and structurally characterized by elemental analyses, single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, photoluminescence spectrum, and magnetic measurements. The structure of 1 exhibits a 2D layer structure, in which the Dy2O2 dimer serves as the building block. The photoluminescence spectrum shows blue luminescence in the solid state at room temperature. Owing to the special frustration structure, unusual magnetic relaxation was found in compound 1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

1,3-Oxazines and their Benzo Derivatives

Abstract: The structures and chemistry of 1,3-oxazine derivatives and their carbo- or heterocycle-fused analogs have been studied thoroughly from various aspects in recent decades. Numerous methods have been devised for the preparation of the variously saturated or substituted derivatives of this family of heterocycles, and are discussed in this chapter with regard to the mode of assembly of the ring atoms. The latest developments in these fields, involving multicomponent reactions, solid-phase procedures, and both conventional and enzymatic catalytic methods of synthetic organic chemistry, allow the highly regio-, stereo-, and enantioselective preparation of these compounds. With the increasing demand for chiral nonracemic molecules, stereoselective methods for the synthesis of 1,3-oxazine derivatives and applications of enantiopure 1,3-oxazines in asymmetric transformations have recently gained in importance. The wide-ranging possibilities for the application of 1,3-oxazine derivatives in organic syntheses have been utilized in the preparation of numerous mono- or difunctional compounds, including key intermediates toward natural products or bioactive substances. Besides the structural and chemical characterization of 1,3-oxazines and their carbo- or heterocycle-fused analogs, their most important biologically active derivatives are also discussed.

6-{[(Benz­yloxy)carbon­yl]­oxy}-2-methyl­hexa­hydro­pyrano[3,2-d][1,3]dioxin-7,8-diyl bis­(chloro­acetate)

Abstract: The asymmetric unit of the title compound, C20H22O10Cl2, consists of a 6-{[(benz­yloxy)carbon­yl]­oxy}group and two chloro­acetate groups bonded to a 2-methyl­hexa­hydro­pyrano[3,2-d][1,3]dioxin group at the carbon 1,2 and 3 positions, respectively, of a pyrano ring fused to a dioxin ring. The dihedral angle between the mean planes of the dioxin and benzyl rings is 42.2 (2)°. An extensive array of weak inter­molecular C—H⋯O hydrogen bonds links the mol­ecules into chains along [011]. Additional weak inter­molecular C—H⋯π inter­actions occur between C—H atoms of the dioxin and benzyl rings and a nearby benzene ring. A MOPAC geometry optimization calculation in vacuo revealed that the dihedral angle between the mean planes of the dioxin and benzyl rings increased by 24.42 to 66.64°, suggesting that the weak inter­molecular hydrogen-bonding inter­actions, in coord­ination with weak C—H⋯π inter­actions, influence the geometry of the resultant crystalline species and help to stabilize the crystal packing.