Chemical investigation of Andrographis serpyllifolia Isolation and structure of serpyllin, a new flavone

A new flavone, Serpyllin, has been isolated from Andrographis serpyllifolia Wt. and its structure has been established as 5-hydroxy-7,8,2′,3′,4′-pentamethoxyflavone by spectral and synthetic evidence. The synthesis of 5,6,7,2′,3′,4′-hexamethoxyflavone is also reported.     

The chemistry of phenalenium system—II 7,8,2′,3′,4′,5′-Hexachloro-11-methoxy-6H-cyclopenta[a]pyrene-6-spiro-1′-cyclopenta-2′,4′-diene

7,8,2′,3′,4′,5′-Hexachloro-11-methoxy-6H-cyclopenta[a]pyrene-6-spiro-1′-cyclopenta-2′,4′-diene 5 has been obtained by the reaction of phenalenone and 1,2,3,4-tetrachlorocyclopentadiene. The gross structure of 5 has been determined by the X-ray analysis. The ground-state properties of 5were discussed from the spectroscopic data, dipole moment and bond lengths.     

Synthesis of ansa-2,2′-bis[(4,7-dimethyl-inden-1-yl)methyl]-1,1′-binaphthyl and nsa-2,2′-bis[(4,5,6,7-tetrahydroinden1-yl)methyl]-1,1′-binaphthyltitanium and -zirconium dichlorides

2,2′-Bis[(4,7-dimethyl-inden-1-yl)methyl]-1,1′-binaphthyl and [2,2′-bis[(4,5,6,7-tetrahydroinden-1-yl)methyl]-1,1′-binaphthyl]titanium and -zirconium dichlorides have been synthesized from 2,2′-bis(bromomethyl)-1,1′-binaphthylene. 2,2′-Bis(bromomethyl)-1,1′-binaphthylene was alkylated with the lithium salt of 4,7-dimethylindene to yield 2,2′-bis[1-(4,7-dimethyl-indenylmethyl)]-1,1′-binaphthylene (S)-(−)-9. The lithium salt of 9 was metalated with either titanium trichloride followed by oxidation or zirconium tetrachloride to give titanocene dichloride (S)-(+)-10 and zirconocene dichloride 11. The known complexes ansa-[2,2′-bis[(1-indenyl)methyl]-1,1′-binaphthyl]titanium and -zirconium dichlorides were formed and hydrogenated to ansa-[2,2′-bis[(4,5,6,7-tetrahydroinden-1-yl)methyl]-1,1′-binaphthyl]titanium and -zirconium dichlorides 12 and 14 or to ansa-[2,2′-bis[(4,5,6,7-tetrahydroinden-1-yl)methyl]-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl]titanium dichloride 13 whose solid state structure was determined by X-ray crystallography. Complex 13 adopts a C₁-symmetrical conformation in the solid state, but is conformationally mobile in solution, exhibiting C₂-symmetry in its room temperature NMR spectra.     

Spiro-dihydrofuran-pyrazolidinones from tetraacetylethylene andazo-dicarbonyl compounds

Tetraacetylethylene (1) reacted with electron-withdrawing azo compounds to give spiro furan-pyrazoles. Their structure was confirmed by an X-ray crystallographic analysis on a derivative of the spiro furan-3(2H),5′(7′H)-pyrazolo 1,2-a1,2,4 triazole-1′,3′,6′-trione. The cycload-ducts show ring-open chain tautomerism.     

Chains, ladders and sheets of d metal–organic polymers generated from the flexible bipyridyl ligands

By use of the three-layer diffusion method, reactions of flexible bipyridyl ligands (4,4′-bpp or 3,3′-bpp) with M(II) salts (M = Zn, Cd) and multi-carboxylate ligands resulted in the formation of four interesting d¹⁰ metal–organic coordination polymers: [Zn(μ-4,4′-bpp)Br₂]_n (1), [Zn(μ-4,4′-bpp)(1,2-bdc)]_n · nH₂O (2), [Zn(μ-3,3′-bpp)(1,3-bdc)]_n · nCH₃OH · 2nH₂O (3) and [Cd(μ-3,3′-bpp)(C₄H₂O₄)]_n · 3nH₂O (4) (4,4′-bpp = 2,2′-bis(4-pyridylmethyleneoxy)-1,1′-biphenylene; 3,3′-bpp = 2,2 ′-bis(3-pyridylmethyleneoxy)-1,1′-biphenylene; bdc=benzenedicarboxylate, C₄H₄O₄ = fumaric acid). Complex 1 has a 2D sheet structure consisting of two unusual zigzag Zn(II) chains which are nearly perpendicular to each other. Complex 2 is comprised of two-leg ladders, in which [Zn(4,4′-bpp)] chains serve as the side rails and 1,2-bdc ligands serve as the cross rungs. In complex 3, every two 1,3-bdc ligands connect the neighbouring Zn(II)-3,3′-bpp dimetallic rings in η¹ coordination modes into an interesting chain structure. Complex 4 consists of an anionic macrocycle-containing cadmium dicarboxylate sheets that are separated by 3,3′-bpp. These d¹⁰ metal complexes exhibit high thermal stabilities and strong luminescence efficiencies.     

Studies of nucleosides and nucleotides—XLVI Purine cyclonucleosides—13. Synthesis and properties of 8,5′-anhydro-8-mercaptoadenosine

Starting from 8-bromoadenosine, 2′,3′-O-isopropylidene-(IIa) and 2′,3′-O-ethoxymethylidene-5′-O-tosyl-8-bromoadenosme (IIb) were synthesized. Compounds IIa, b gave 8,5′-anhydronucleosides (IV a and b) on treatment with hydrogen sulfide in pyridine or aqueous sodium hydrogen sulfide in pyridine at −5–−15°. The structure of IV was confirmed by UV absorption, NMR and elemental analysis. CD and ORD measurements of IV showed large positive Cotton effects around absorption maxima. Acidic removal of the protecting group in IV gave 8,5′-anhydro-8-mercaptoadenosine (V), which was desulfurized to afford 5′-deoxyadesine (VI).     

Ab initio study of rotational isomerism and electronic structure of isomeric bipyrroles

Ab initio calculations using STO-3G and 4-31G basis sets have been performed on the internal rotation barriers and conformational stabilities for 2,3′- and 3,3′-bipyrrole. The twofold rotation potential predicted for both isomers at minimal basis level becomes a more involved fourfold potential when the split-valence basis set is employed, because it takes into account more properly the nonbonded interannular interactions. A transoid-gauche minimum is predicted to have the minimal absolute conformational energy in both isomers. The electronic structure of the highest occupied MOs of 2,2′-, 2,3′- and 3,3′-bipyrrole are analyzed in terms of the single pyrrole MO pattern and a similar difficulty in removing electrons from the HOMOs in going from one isomer to another is predicted, even if a deviation from planarity occurs.     

Analysis of the diffuse bands near 6100 Å in the fluorescence spectrum of Cs2

The diffuse bands near 6100 Å in the laser-induced fluorescence spectrum of Cs₂ are analyzed through quantum-mechanical spectral simulations. These bands are interpreted as bound-free emission to the vibrational continuum of the ground state from an excited state of ion-pair character. The lower region of this state, which we have labeled E′, is described approximately by the spectroscopic constants, T_e = 19400 cm⁻¹, R_e = 9 Å, and ω_e = 13 cm⁻¹. Experiments with a single-mode Ar⁺ laser as excitation source clearly reveal fine structure in the E′ → X spectrum, which was not evident for multimode laser excitation. This fine structure confirms our analysis and supports our suggestion that extensive averaging over initial (υ′, J′) levels is responsible for the absence of fine structure in the spectra excited by a multimode laser. Various averaging mechanisms are investigated in the spectral calculations. The paper includes a brief review of other work on “structured continua” in diatomic spectra, and a semiclassical treatment of such structure, with emphasis on the distinction between “reflection” structure and “interference” structure.     

Alkaloids of glycosmis pentaphylla (Retz.) correa

The isolation of skimmianine and three new acridone alkaloids from the root bark of Glycosmis pentaphylla (Retz.) Correa is reported. Based on the spectral evidence and chemical correlations, these are shown to be hitherto naturally unknown noracronycine (IIb), des-N-methyl-acrocynine (IXa) and des-N-methylnoracronycine (IXb). Evidence is also presented to show that of the two possible structures, 1-methoxy-2′,2′,10-trimethylpyrano(5′,6′-2,3 or 3,4) acridone (Ia or IIa) for acronycine, the angular structure IIa is correct.     

Synthesis and characterisation of monomeric, dimeric and polymeric ferrocenylacetylides. Crystal structure of 1,1′-bis(phenylethynyl)ferrocene

The reactions of alkynyltrimethylstannanes with 1,1′-dilithioferrocene have given several ferrocenylacetylides, namely 1-pheny]-ethynyl-1′-iodo-ferrocene (1), 1,1′-bis(phenylethynyl)ferrocene (2), 1,4-di(1′-iodoferrocenylethynyl)benzene (3) and poly[1,4-(1′-ferrocenylethynyl)ethynylbenzene] (4). The versatility of this reaction for the formation of ferrocenylacetylides is demonstrated. The crystal structure of 2 has been determined, and shown to involve a linear array of the groups with a cis arrangement of the phenylethynyl ligands.     

Homoleptic carbene complexes VI. Bis{1,1′-methylene-3,3′-dialkyl-diimidazolin-2,2′-diylidene}palladium chelate complexes by the free carbene route

1,1′-Methylene-3,3′-dialkyldiimidazolium salts have been deprotonated with n-butylithium in the presence of palladium(II) iodide to give the percarbene complexes 1 (alkyl=Me) and 2 (alkyl=Et), each containing two bidentate 1,1′-methylene-3,3′-dialkyldiimidazolin-2,2′-diylidene chelate ligands. The X-ray structure analysis of 1 reveals a stereochemistry in which the two spiro-linked six-membered metallacycles adopt boat-like conformations strongly bending out of the PdC₄ coordination plane in opposite directions. The carbenoid imidazole rings, which are rotated by +42 and −43°, respectively, relative to this plane, break down into two tightly bound π-systems (N=4C=4N,= C=C) connected by long C---N bonds.     

Rotational and hyperfine structure in the BΠ0+excited state of ICl

For the diatomic molecule ICl the rotational structure of the three lowest vibrational states υ′ = 0, 1, 2 and the hyperfine structure of υ′ =     

Analysis of 5-hydroxy-7-methoxyflavones by normal-phase high-performance liquid chromatography

The separation and identification of flavones present in a chloroform extract of Baccharis trinervis leaves was investigated. The chromatographic system consisted of a amino-bonded column, gradient elution from hexane-chloroform (85:15) to chloroform-acetonitrile (40:60) and detection at 346 nm. Four flavones were found. From NMR and MS data they were identified as 5-hydroxy-7,4′-dimethoxyflavone (I), 5-hydroxy-7,3′,4′-trimethoxyflavone (II), 5,3′-dihydroxy-7,4′-dimethoxyflavone (III) and 5,4′-dihydroxy-7-methoxyflavone (IV). Flavone II and III have not been found in Baccharis trinervis before. The chromatographic system showed good selectivity for the separation of the flavones. The relation between t_R and the structure is discussed.     

Azacrown ethers containing oximic and Schiff base sidearms - potential heteronuclear metal ion receptors

A simple synthetic pathway for the preparation of oxime- and Schiff base-containing aza- and diazacrown ethers is reported. N-Methoxymethyl-substituted aza-15-crown-5 and aza-18-crown-6 as well as N,N′-bis(methoxymethyl)-substituted diaza-18-crown-6 were treated with 5-bromosalicylaldehyde to produce the N-(2′-hydroxy-3′-carbonyl-5′-bromobenzyl)-substituted aza-15-crown-5 (8), aza-18-crown-6 (9) and N,N′-bis(2′-hydroxy-3′-carbonyl-5′-bromobenzyl)-substituted diaza-18-crown-6 (10) compounds. Compounds 8 and 10 were treated with hydroxylamine to give oxime-substituted ligands 12 and 13. A series of bis-Schiff base-containing diaza-18-crown-6 ligands were prepared by reacting 10 with 2-hydroxyaniline (to form 14), 5-nitro-2-hydroxyaniline (15), 2-aminopyridine (16), 2-hydrazinopyridine (17) and N-aminomorpholine (18). Compounds 12–18 are potential complexing agents for simultaneous binding of soft transition and hard alkali or alkaline earth metal ions in one molecule. These new oxime- and Schiff base-containing ligands interacted strongly with Na⁺ and K⁺ in methanol. The interaction of the aromatic portions of 9, 10, and 12–15 with transition metal ions was shown by the UV spectra of the metal ion complexes in 50% aqueous DMF. The X-ray structure of 10 is reported.     

H, C, N NMR, ESI mass spectral and single crystal X-ray structural characterization of three spiro[pyrrolidine-2,3′-oxindoles]

Three spiro[pyrrolidine-2,3′-oxindoles], 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-phenyl-spiro[3H-indole-3,3′-[3H]-pyrrolizine]-2′-carboxylic acid methyl ester (1), 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-phenyl-spiro[3H-indole-3, 3′-[3H]-pyrrolizine] (2) and 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-(4″-chlorophenyl)-spiro[3H-indole-3,3′-[3H]-pyrrolizine] (3) have been synthesized and their ¹H, ¹³C and ¹⁵N spectra assigned. The chemical shift assignments are based on Pulsed Field Gradient (PFG) Double Quantum Filter (DQF) ¹H, ¹H correlation spectroscopy (COSY), PFG ¹H, ¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,X (X = ¹³C and ¹⁵N) Heteronuclear Multiple Bond Correlation (HMBC) experiments. The single crystal X-ray structures of 1–3 have been determined. Compounds 1 and 2 crystallized in monoclinic space group C2/c and compound 3 in monoclinic space group P2₁/c, respectively. Also the ESI-TOF MS data of 1–3 are given.     

Anion radicals of some fluorobiphenyls

Potassium 4,4′-difluorobiphenylide, 4-fluorobiphenylide and potassium 3,3′-difluorobiphenylide are stable at −80° in the tetrahydrofuran. 4-Chlorobiphenyl, 4-bromobiphenyl and 4,4′-dibromobiphenyl apparently react with potassium at low temperatures to form radicals which decompose immediately by halide elimination. The ESR spectra of the 4,4′-difluorobiphenylide and 3,3′-difluorobiphenylide radicals and the polarographic behaviour, p-band positions, and results of LCAO---MO calculations for the parent, neutral compounds are reported.     

Synthesis of sulfur analogues of methyl and allyl kojibiosides and methyl isomaltoside and conformational analysis of the kojibiosides

The synthesis of methyl and allyl 5′-thio--D-kojibiosides and methyl 5′-thio--D-isomaltoside is described. The phenylselenoglycoside and trichloroacetimidate of 2,3,4,6-tetra-O-acetyl-5-thioglucose have been employed as glycosyl donors to glycosylate glucopyranosyl acceptors with 2-OH and 6-OH positions free. The disaccharides thus obtained are potential glucosidase inhibitors. The conformational preferences of allyl 5′-thiokojibioside (34) were studied by comparison of experimental NOE curves with the theoretical counterparts for the corresponding methyl glycoside 25, derived from a Boltzmann-averaged grid search using the program PIMM91. Very good agreement of experimental NOE curves derived from selective NOE measurments with the theoretical curves is found. The data are consistent with the population of a global minimum structure (Φ=−43, Ψ=−39 degrees) to the extent of 90%, and a second local minimum (Φ=−36, Ψ=−173 degrees) to the extent of 6%. An X-ray crystal structure of 34 at 190 K (R=4.2%) indicates a conformation (Φ=−46, Ψ=−23 degrees) that is similar to that of the global minimum.     

Flavonoids of citrus—VIII Synthesis of Limocitrol, limocitrin and spinacetin

Allan-Robinson syntheses of limocitrol (3,5,7,4′-tetrahydroxy-6,8,3′-trimethoxyflavone), limocitrin (3,5,7,4′-tetrahydroxy-8,3′-dimethoxyflavone) and spinacetin (3,5,7,4′-tetrahydroxy-6-3′- dimethoxyflavone) are described. The direction of ring closure to give limocitrin or spinacetin is determined by the blocking group (benzyl or benzoyl) at the 4-position of the B-ring component.     

3-exo,3′-exo-(1R,1′R)-Bithiocamphor — a versatile source for functionally different 3,3′-bibornane derivatives, II. 1 An access to 3-exo,3′-exo-(1r,1′r)-bicamphor and related compounds

3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduction of 12 with L1AlH₄ affords the 3,3′-biisoborneol 16. Further related transformations to various 2,2′-difunctional 3,3′-bibornane derivatives are described, which are could be of interest as chiral ligands     

Synthetic analogues of wedelolactone

The syntheses of 7′-methoxy- and 5′,7′,6-trimethoxy-coumarino(3′,4′:3,2)coumarones (IIa and IIb) are described.