Identification of the Key Enzyme of Roseoflavin Biosynthesis

The bacteria Streptomyces davawensis and Streptomyces cinnabarinus produce roseoflavin, the only known natural riboflavin (vitamin B₂) analogue with antibiotic activity. Roseoflavin can be considered a natural antimetabolite and has been postulated to be biosynthesized from riboflavin via the key intermediate 8‐demethyl‐8‐aminoriboflavin (AF). The required site‐specific substitution of one of the methyl groups on the dimethylbenzene ring of riboflavin by an amino group (to give AF) is challenging. The pathway from riboflavin to AF has remained elusive, and the corresponding enzyme/s was/were unknown. Herein, we show by systematic gene deletion, heterologous gene expression, and biochemical studies that the enzyme specified by the gene BN159_7989 from S. davawensis is able to carry out a whole set of chemical reactions starting from riboflavin‐5′‐phosphate to give the final product 8‐demethyl‐8‐aminoriboflavin‐5′‐phosphate (AFP).     

5‐Ethyl‐2′‐deoxy‐4′‐thiouridine (R)‐S‐oxide monohydrate

The pyrimidine ring of the title compound, C₁₁H₁₆N₂O₅S·H₂O, is planar to within 0.026 (1) Å and makes an angle of 77.73 (8)° with the mean plane of the thiosugar ring. In terms of standard nucleoside nomenclature, this ring has a C1′‐exo,C2′‐endo conformation. The O5′—C5′—C4′—C3′ torsion angle is ?167.4 (2)° and the glycosidic S4′—C1′—N1—C2 torsion angle is ?101.8 (2)° (anti).     

Two phosphate–imidazole complexes with and without a hydrogen‐bonded guest mol­ecule

The mol­ecular structures of the complexes imidazolium 6,6′‐di‐tert‐butyl‐4,4′‐dimethyl‐2,2′‐thio­diphenyl phosphate, C₃H₅N₂⁺·C₂₂H₂₈O₄PS⁻, (I), and imidazolium 6,6′‐di‐tert‐butyl‐4,4′‐dimethyl‐2,2′‐thio­diphenyl phosphate diisopropyl hydrazo­dicarboxyl­ate hemisolvate, C₃H₅N₂⁺·C₂₂H₂₈O₄PS⁻·0.5C₈H₁₆N₂O₄, (II), have been determined. While (I) forms the expected hydrogen‐bonded chain utilizing the two imidazole N‐bound H atoms, in (II), the substituted hydrazine solvent mol­ecule inserts itself between the chains. Compound (I) exhibits a strong N—H⋯O hydrogen bond, with an N⋯O distance of 2.603 (2) Å. The hydrazine solvent molecule in (II) lies about a twofold axis and the N‐bound H atoms are involved in bifurcated hydrogen bonds with phosphate O atoms. A C‐bound H atom of the imidazolium cation is involved in a C—H⋯O inter­action with a carbonyl O atom of the hydrazine solvent mol­ecule.     

Synthesis,Structure, and Clathration Ability of the Microporous Three‐Dimensional Coordination Polymer [{CuCN(4,4′‐bpy)} · 2(4,4′‐bpy)]

The respectively yellow and red coordination polymers [(CuCN)₂(μ‐4,4′‐bpy)] ( 1 ) and [{CuCN(μ‐4,4′‐bpy)} · 2(4,4′‐bpy)] ( 2 ) (4,4′‐bpy = 4,4′‐bipyridine) may be prepared by self‐assembly of CuCN and 4,4′‐bpy at the appropriate molar ratio in acetonitrile solution at 100 °C. In 1 infinite CuCN chains are linked by 4,4′‐bpy ligands into lamellar polymers which exhibit short Cu…C(N) contacts of 2.41(1) Å between one of the crystallographically independent copper atoms and cyanide carbon atoms of a neighbouring corrugated sheet. At a molar ratio of CuCN : 4,4′‐bpy below 2 : 3, the heteroaromatic ligands also adopt a structure‐directing role to afford 3 , in which [(CuCN)₂(μ‐4,4′‐bpy)] sheets are now joined by additional bridging 4,4′‐bpy spacer molecules to provide a three‐dimensional framework, whose nanometer‐sized channels (12.76 × 13.12 Å) accomodate two noncoordinated 4,4′‐bpy guest molecules. A DTA/TGA trace demonstrates that these can be removed in two steps at 150 and 176 °C.     

Bis(4,4′‐bi­pyridine‐κN)­bis­(hydrogen phthalato)‐κ2O,O′;κO‐zinc(II)

The title compound, [Zn(C₈H₅O₄)₂(C₁₀H₈N₂)₂], was obtained by the hydro­thermal reaction of ZnSO₄·7H₂O with phthalic acid (H₂pht) and 4,4′‐bi­pyridine (4,4′‐bipy). Crystallographic analysis shows that it has a one‐dimensional double‐chain structure via hydrogen‐bonding interactions. Each Zn^II atom, adopting a distorted tetrahedral geometry, is coordinated by two N atoms from two 4,4′‐bipy ligands, with Zn—N distances of 2.054 (4) and 2.104 (4) Å, and by two O atoms from symmetry‐related Hpht⁻ ligands, with Zn—O distances of 1.921 (4) and 2.019 (4) Å.     

Preparation and Structure Determination of SrMn2(PO4)2 and Redetermination of b ′‐Mn3(PO4)2

Pale rose single crystals of SrMn₂(PO₄)₂ were obtained from a mixture of SrCl₂ · 6 H₂O, Mn(CH₃COO)₂, and (NH₄)₂HPO₄ after thermal decomposition and finally melting at 1100 °C. The new crystal structure of strontium manganese orthophosphate [P‐1, Z = 4, a = 8.860(6) Å, b = 9.054(6) Å, c = 10.260(7) Å, α = 124.27(5)°, β = 90.23(5)°, γ = 90.26(6)°, 4220 independent reflections, R1 = 0.034, wR2 = 0.046] might be described as hexagonal close‐packing of phosphate groups. The octahedral, tetrahedral and trigonal‐bipyramidal voids within this [PO₄] packing provide different positions for 8‐ and 10‐fold [SrO_x] and distorted octahedral [MnO₆] coordination according to a formulation Mn Mn Mn Sr (PO₄)₄. Single crystals of β′‐Mn₃(PO₄)₂ (pale rose) were grown by chemical vapour transport (850 °C → 800 °C, P/I mixtures as transport agent). The unit cell of β′‐Mn₃(PO₄)₂ [P2₁/c, Z = 12, a = 8.948(2) Å, b = 10.050(2) Å, c = 24.084(2) Å, β = 120.50°, 2953 independent reflections, R1 = 0.0314, wR2 = 0.095] contains 9 independent Mn²⁺. The reinvestigation of the crystal structure led to distinctly better agreement factors and significantly reduced standard deviations for the interatomic distances.     

Synthesis and Characterization of Two New Transition‐Metal Complex Salts of the Wells‐Dawson Polyanion

Two new transition‐metal (TM) complex salts of the Wells‐Dawson polyanion: [Cu(2,2′‐bpy)₃]₂[Cu(2,2′‐bpy)₂]₂[P₂W₁₈O₆₂] ( 1 ) and [2,2′‐bpy]₈[Fe(2,2′‐bpy)₃]₈[P₂W₁₈O₆₂]₄·9H₂O ( 2 ) (2,2′‐bpy = 2,2′‐bipyridine), have been synthesized under hydrothermal conditions by using pre‐prepared α‐K₆P₂W₁₈O₆₂·15H₂O as a precursor. Crystal data for compound 1 : monoclinic, space group C2/c, a = 20.722(4) Å, b = 21.988(4) Å, c = 29.614(6) Å, β = 104.32(3)°, V = 13074(5) ų, Z = 4; for compound 2 : triclinic, space group , a = 15.804(3) Å, b = 27.519(6) Å, c = 27.566(6) Å, α = 72.71(3)°, β = 89.94(3)°, γ = 89.90(3)°, V = 11447(5) ų, Z = 1. Compounds 1 and 2 have been characterized by single‐crystal X‐ray diffraction, IR spectra, thermogravimetric analysis, XPS spectra and cyclic voltammetry. The two compounds were used as solid bulk modifiers to fabricate bulk‐modified carbon paste electrodes ( 1 ‐, 2 ‐CPE). The electrochemical behaviors of 1 ‐, 2 ‐CPE have been studied in detail. The redox behavior of the parent Wells‐Dawson type cluster was maintained completely in compounds 1 and 2 .     

Cocrystallization of adamantane‐1,3‐dicarboxylic acid and 4,4′‐bipyridine

The cocrystallization of adamantane‐1,3‐dicarboxylic acid (adc) and 4,4′‐bipyridine (4,4′‐bpy) yields a unique 1:1 cocrystal, C₁₂H₁₆O₄·C₁₀H₈N₂, in the C2/c space group, with half of each molecule in the asymmetric unit. The mid‐point of the central C—C bond of the 4,4′‐bpy molecule rests on a center of inversion, while the adc molecule straddles a twofold rotation axis that passes through two of the adamantyl C atoms. The constituents of this cocrystal are joined by hydrogen bonds, the stronger of which are O—H...N hydrogen bonds [O...N = 2.6801 (17) Å] and the weaker of which are C—H...O hydrogen bonds [C...O = 3.367 (2) Å]. Alternate adc and 4,4′‐bpy molecules engage in these hydrogen bonds to form zigzag chains. In turn, these chains are linked through π–π interactions along the c axis to generate two‐dimensional layers. These layers are neatly packed into a stable crystalline three‐dimensional form via weak C—H...O hydrogen bonds [C...O = 3.2744 (19) Å] and van der Waals attractions.     

The complex of dicarbonyl(methylcyclopentadienyl)molybdenum with carbonyl(cyclopentadienyl)nitrosyl[tris(phenylacetylenide)stannyl]manganese: Synthesis and molecular formula

A reaction of CpMn(CO)(NO)Sn(C=CPh)₃ (I) with [Cp′Mo(CO)₂]₂ (Cp′ = MeC₅H₄) gave CpMn(CO)(NO)Sn(C=CPh)₃[Cp′Mo(CO)₂]₂ (II) as dark red prismatic crystals. The molecular structure of complex II was determined by X-ray diffraction study. Complex II contains the Mo-Mo bond (2.9799(5) Å), which is perpendicular to the coordinated C=C bond. The latter is longer (1.371(5) Å) than free acetylenide fragments (1.190(5) and 1.198(5) Å). In addition, the angle Sn-C=C for the coordinated C=C bond is smaller (134.1(3)°) than that in free fragments (173.5(4)° and 171.9(4)°). The Mn-Sn bond length in complex II (2.5662(7) Å) is close to that in complexI (2.5328(17) Å) and is much shorter than the sum of the corresponding covalent radii (2.78 Å). The Sn-C bond (2.108(4) Å) in the acetylenide fragment π-bound to two Mo atoms (average Mo-C, 2.19 Å), as well as the other Sn-C bonds (2.119(4) and 2.135(4) Å), remains virtually the same as in complex I (average 2.105 Å).     

A synchrotron‐radiation study of the lactone form of rhodamine B at 120 K

The structure of the lactone form of rhod­amine B, 3,6‐bis­(diethyl­amino)‐1′,3′‐di­hydro­spiro­[xanthene‐9,3′‐isobenzo­furan]‐1′‐one, C₂₈H₃₀N₂O₃, has been determined at 120 K using synchrotron radiation at a wavelength of 0.496 Å. The structure contains two independent rhod­amine B mol­ecules with virtually identical geometry. The xanthene main planes of the mol­ecules are inclined at an angle of 41.6 (2)° to one another. Molecule 2 has a statistically disordered ethyl group, with 71% in one orientation and 29% in a second orientation. The lactone C—O bonds are 1.497 (1) and 1.495 (1) Å. There are no classical hydrogen bonds, but the structure is stabilized by two short C?O interactions. The crystals of the lactone form were produced by a novel hydro­thermal reaction.     

Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): a finite cyclic 1:1 adduct with 2,2′‐dipyridyl­amine

In ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–2,2′‐dipyridyl­amine (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₀H₉N₃, (I), there is an intramolecular O—H?O hydrogen bond [H?O 2.03 Å, O?O 2.775 (2) Å and O—H?O 147°] in the ferrocenediol component, and the two neutral molecular components are linked by one O—H?N hydrogen bond [H?N 1.96 Å, O?N 2.755 (2) Å and O—H?N, 157°] and one N—H?O hydrogen bond [H?O 2.26 Å, N?O 3.112 (2) Å and N—H?O 164°] forming a cyclic R(8) motif. One of the pyridyl N atoms plays no part in the intermolecular hydrogen bonding, but participates in a short intramolecular C—H?N contact [H?N 2.31 Å, C?N 2.922 (2) Å and C—H?N 122°].     

5‐Methyl‐2′‐deoxy‐4′‐thio‐α‐uridine (R)‐­S‐oxide

The pyrimidine ring of the title compound, C₁₀H₁₄N₂O₅S, is planar to within 0.024 (1) Å and makes an angle of 75.46 (10)° with the mean plane of the thio­sugar ring. In terms of standard nucleoside nomenclature, this ring has the C3′‐endo conformation. The O5′—C5′—C4′—C3′ torsion angle is 166.5 (3)° and the glycosidic torsion angle S4′—C1′—N1—C2 is ?52.1 (2)° (syn).     

A new photochromic tetra­hydro­indolizine

The title compound, di­methyl 10b′‐(4‐fluoro­styryl)‐8′,9′‐di­methoxy‐4‐nitro‐5′,6′‐di­hydrospiro­[9H‐fluorene‐9,1′(10b′H)‐pyrrolo­[2,1‐a]­iso­quinoline]‐2′,3′‐di­carboxyl­ate, C₃₈H₃₁FN₂O₈, is a new photochromic tetra­hydro­indolizine. One of the C—C bonds at the spiro C atom is very long [1.630 (2) Å], thus explaining the photochromic behaviour.     

Preparation and Intramolecular CC Coupling Reaction for Bis‐benzimidazolium Salt

Bis‐benzimidazolium salt 1 was prepared via a series of reactions using 2,2′‐diphenol as starting material. Compound 2 was afforded through the intramolecular C? C coupling reaction of 1 under the catalysis of Pd(OAc)₂. The structure of 2 is characterized through X‐ray diffraction analyses, ¹H NMR and ¹³C NMR. In 2 , two boat‐like seven‐membered rings are contained, where the C? C bond distance newly formed is 1.461(5) Å, and it is between regular C? C single bond (1.54 Å) and C?C double bond (1.34 Å). This shows that new C? C bond has partial double‐bond character. In the crystal packing of 2 , the 2D supramolecular layers are formed via C? H···F hydrogen bond.     

Experimental Study of Hydrogen Bonding Potentially Stabilizing the 5′‐Deoxyadenosyl Radical from Coenzyme B12

Coenzyme B₁₂ can assist radical enzymes that accomplish the vicinal interchange of a hydrogen atom with a functional group. It has been proposed that the Co? C bond homolysis of coenzyme B₁₂ to cob(II)alamin and the 5′‐deoxyadenosyl radical is aided by hydrogen bonding of the corrin C19? H to the 3′‐O of the ribose moiety of the incipient 5′‐deoxyadenosyl radical, which is stabilized by 30 kJ mol^?1 (B. Durbeej et al., Chem. Eur. J. 2009 , 15, 8578–8585). The diastereoisomers (R)‐ and (S)‐2,3‐dihydroxypropylcobalamin were used as models for coenzyme B₁₂. A downfield shift of the NMR signal for the C19? H proton was observed for the (R)‐isomer (δ=4.45 versus 4.01 ppm for the (S)‐isomer) and can be ascribed to an intramolecular hydrogen bond between the C19? H and the oxygen of CHOH. Crystal structures of (R)‐ and (S)‐2,3‐dihydroxypropylcobalamin showed C19? H???O distances of 3.214(7) Å (R‐isomer) and 3.281(11) Å (S‐isomer), which suggest weak hydrogen‐bond interactions (?ΔG<6 kJ mol^?1) between the CHOH of the dihydroxypropyl ligand and the C19? H. Exchange of the C19? H, which is dependent on the cobalt redox state, was investigated with cob(I)alamin, cob(II)alamin, and cob(III)alamin by using NMR spectroscopy to monitor the uptake of deuterium from deuterated water in the pH range 3–11. No exchange was found for any of the cobalt oxidation states. 3′,5′‐Dideoxyadenosylcobalamin, but not the 2′,5′‐isomer, was found to act as a coenzyme for glutamate mutase, with a 15‐fold lower k_cat/K_M than 5′‐deoxyadenosylcobalamin. This indicates that stabilization of the 5′‐deoxyadenosyl radical by a hydrogen bond that involves the C19? H and the 3′‐OH group of the cofactor is, at most, 7 kJ mol^?1 (?ΔG). Examination of the crystal structure of glutamate mutase revealed additional stabilizing factors: hydrogen bonds between both the 2′‐OH and 3′‐OH groups and glutamate 330. The actual strength of a hydrogen bond between the C19? H and the 3′‐O of the ribose moiety of the 5′‐deoxyadenosyl group is concluded not to exceed 6 kJ mol^?1 (?ΔG).     

μ‐(4,4′‐Bi­pyri­dine)‐N:N′‐bis[bis‐(pyrrol­idine­dithio­car­boxyl­ato‐S,S′)zinc(II)]

The title compound, [Zn₂(C₅H₈NS₂)₄(C₁₀H₈N₂)], consists of two bis(pyrrol­idine­dithio­carboxylato)­zinc molecules bridged by a 4,4′‐bi­pyridine molecule, and has a 222 symmetry. Each Zn atom forms a five‐coordinate pseudo‐square‐based pyramidal arrangement, with four Zn—S interactions and one Zn—N interaction; the Zn—N distance is 2.085 (3) Å and the Zn—S distances are in the range 2.3319 (8)–2.6290 (9) Å.     

Poly­sulfonyl­amines. CXLV.

The prominent features in the molecular structure of the title compound (alternative name: 2‐diethyl­carbamoyl‐1,1,3,3‐tetraoxo‐1,3,2‐benzodi­thia­zole), C₁₁H₁₄N₂O₅S₂, arise in the urea moiety S₂N—C(O)—N′C₂: the sum of the angles at N is 332.3 (1)°, the N—C(O)—N′C₂ unit is planar, and distances N—C(O) = 1.494 (3) Å, N′—C(O) = 1.325 (2) Å and C—O = 1.215 (2) Å. The mol­ecules are associated via five C—H?O hydrogen bonds to form layers parallel to the yz plane. This compound and its di­methyl homologue, which were synthesized by treating the silver salt of o‐benzene­disulfon­imide with carbamoyl chlorides, are prone to rapid hydro­lysis at the weak N—C(O) bond. For both mol­ecules, the rotational barrier about the partial N′—C(O) double bond is ca 50 kJ mol^?1 at 250 K (from dynamic ¹H NMR experiments).     

Hydrothermal Synthesis and X‐ray Crystal Structure of Four Inorganic‐Organic Hybrid Compounds in Vanadium /Copper Iodate Family

Four inorganic‐organic hybrid compounds with the formulae (1,10‐phen)(VO₂)(IO₃) ( 1 ), (2,2′‐bipy)(VO₂)(IO₃) ( 2 ), [Cu₃(2,2′‐bipy)₃Cl₃(IO₃)₂]·I_1.5 ( 3 ), and [Cu(2,2′‐bipy)(H₂O)(IO₃)₂]· (H₂O)₂ ( 4 ) are hydrothermally synthesized at 120 °C for 6 d and characterized by single‐crystal X‐ray diffraction. The use of two different bidentate organodiamine ligands 1,10‐phen and 2,2′‐bipy in the V/I/O system gives rise to compounds 1 and 2 , which crystallize in a monoclinic system with the space group C2/c, a = 17.8131(6) Å, b = 15.0470(7) Å, c = 12.9902(4) Å, β = 133.095(2)°, V = 2542.49(17) ų for 1 and space group P2₁/c, a = 13.3095(5) Å, b = 15.0993(8) Å, c = 13.0454(4) Å, β = 116.971(2)°, V = 2335.88(17) ų for 2 . The use of the bidentate organodiamine ligand 2,2′‐bipy in the Cu/I/O system gives rise to the variety in the structure of products 3 and 4 , which crystallize in a triclinic system with the same space group . a = 8.5143(2) Å, b = 10.4908(3) Å, c = 22.8420(6) Å, α = 93.769(10)°, β = 91.723(10)°, γ = 112.111(10)°, V = 1882.83(9) ų for 3 and a = 6.731(6) Å, b = 10.110(4) Å, c = 12.899(6) Å, α = 106.00(5)°, β = 95.45(4)°, γ = 107.69(6)°, V = 788.4(9) ų for 4 . The solid‐state structures of the compounds 1 and 2 have chains with repeat units of alternative corner sharing of [VO₄N₂] octahedra and [IO₃] pyramids. Compound 3 is a chain containing [IO₃] pyramids and [VO₄N] square pyramids and compound 4 consists of Cu(2,2′‐bipy)²⁺ linked by one water molecule and two [IO₃] pyramids. The thermal stabilities of the compounds are investigated.     

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series, namely 8‐formyl‐7‐hydroxy‐3′,3′‐dimethylspiro[2H‐chromene‐2,1′(3′H)‐2‐benzofuran], C₁₉H₁₆O₄, is reported. In the crystalline state, dimers are formed as a result of the π–π stacking of aromatic groups of the 2H‐chromene part of the molecule and C—H...O interactions. The C_spiro—O bond length in the pyran ring is 1.4558 (10) Å, which is longer than or equal to the bond length in thermo‐ and photochromic 2‐oxaindane spiropyrans synthesized previously, except for the 7,8‐benzo/6‐NO₂ derivative, in which this bond length is 1.465 (2) Å.     

π Groups in ion pair bonding: the structural effects of reduction on the olefinic bond as observed in the molecular structure of Δ9,9′-bifluorenyl bis(lithium tetramethylethylenediamine)

The reaction of 9,9′-bifluorene with n-butyllithium in the presence of tetramethylethylenediamine (TMEDA) results in the formation of Δ^9,9′-bifluorenyl bis-(lithium tetramethylethylenediamine). In the molecular structure of this material, which formally can be considered to be the dianion of the olefin Δ^9,9′-bifluorene, two TMEDALi groups are closely associated with the 9,9′ bond. The fluorenyl groups are twisted relative to each other by an angle of 48.0(5)°, as compared to 42° in the parent olefin. The 9,9′ bond length is increased from 1.39(2) Å in Δ^9,9′-bifluorene to 1.487(5)Å in the dianion.Single crystal X-ray diffraction techniques were used and resulted in a final discrepancy factor of R_w = 0.064 for 2426 observations. The crystal system is monoclinic (C2/c) with a = 10.814(3), b = 16.717(6) and c = 19.766(6) Å, β = 102.55(2)°; ?_obs = 1.10(3) g cm^?3; ?_calc = 1.095 g cm^?3 for four molecules per unit cell.