Synthesis of (+)-carpamic acid from (+)-alanine

(+)-Carpamic acid [(2′R,5′S,6′S)-8-(5′-hydroxy-6′-methylpiperidin-2′-yl)octanoic acid, 1] was synthesized from (S)-alanine, employing intramolecular and reductive amination of acyclic amino ketone 8 as the key step to generate the piperidine ring.     

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.     

Oligomeric flavanoids. Part 13. Synthesis of profisetinidins based on (−) robinetinidol and (+) -epifisetinidol

Acid-catalyzed condensation of (+)-mollisacacidin-[(2R, 3S, 4R)-2, 3-trans-3, 4-trans-flavan-3,3′,4,4′,7-pentaol] with an excess of (−)-robinetinidol[(2R,3S)-2,3-trans-flavan-3,3′,4′,5′,7-pentaol] afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins. They are accompanied by (−)-fisetinidol-(4,2′)-(−)-robinetinidol which results from the pyrogallol B-ring of (−)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate. Similar condensation with (+)-epifisetinidol[(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] led to the exclusive formation of [4,6]-interflavanyl bonds, these units being ‘linearly’ arranged in the tetraflavanoid analogue in contrast to the ‘branched’ nature of the (−)-robinetinidol homologue.     

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.     

Syntheses of some tetralones related to tetracyclines

Syntheses of 5-chloro-8-methoxy-1-tetralone (XIV), 6,8-dimethoxy-1-tetralone (XIX), 2-carbethoxy-6,8-dimethoxy-1-tetralone (VI), 3-(2′-chloro-5′-methoxybenzyl)-6,8-dimethoxy-1-tetralone (III) and 2-carbethoxy-3-(2′-chloro-5′-methoxybenzyl)-6,8-dimethoxy-1-tetralone (IV) are reported. The mode of cyclization with polyphosphoric acid of I and related compounds is described.     

A new example of stereoisomerism in inorganic chemistry: PtRu chiral axis in [(η-p-cymene)RuCl(μ-N,N′-dialkyldithiox-amidato N,N′-Ru-S,S′Pt)Pt(2-diphenylphosphinopyridine)Cl]

The novel compounds [(η⁶-p-cymene)RuCl(μ-RR-DTO N,N′Ru S,S′-Pt)Pt(RR-DTO)(P-N)Cl] (P-N = 2-diphenylphosphino-pyridine, RR-DTO = N,N′-dialkyl-dithioxamidato, R = benzyl, 1; R = (R)-(−)-2-hydroxypropyl (coming from (R)-(−)-2-hydroxypropyl-amine), 2;) exhibit a Pt---Ru chiral axis which is a new example of stereoisomerism in inorganic chemistry. The crystal structure of 2 is also reported.     

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.     

Thermal condensation of imidazole with trifluoroacetaldehyde

The title condensation occurred readily at reflux (100°C) with the methyl hemiacetal of trifluoroacetaldehyde and provided 37.3% of 4(5)-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole as the major product, together with 8.8% of 2-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole, 7.2% of 2,4(5)-bis-(1′-hydroxy-2′,2′,2′-trifluoroethyl)imidazole and 0.4% of the 4,5-bis-product. (Trifluoroacetyl)imidazoles were prepared by oxidation of these condensation products. Nitration and bromination of the condensation products gave the corresponding nitro- and bromoimidazoles, respectively.     

Synthesis of new thiazole analogues of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia. A new conversion of thiazolines into thiazoles

Three pyochelin analogues and their methyl esters all containing a thiazole ring have been synthesised from the same Weinreb amide key intermediate. One of these analogues called HPTT-COOH, a molecule released in the course of pyochelin and yersiniabactin biosynthesis, was efficiently synthesised using a new base induced conversion of the key compound 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide into 2′-(2-hydroxyphenyl)-2′-thiazole-4′-(N-methoxy,N-methyl) carboxamide.     

Synthesis of optically active forms of sulcatol : The aggregation pheromone in the scolytid beetle, Gnathotrichus sulcatus

(S)-(+)-Sulcatol (1) and its antipode (1′) were synthesized from (R)-(−)-glutamic acid (2), and its antipode (2′), respectively. This established the absolute configurations of both enantiomers of sulcatol and afforded key materials to study the relationship between pheromone activity and chirality.     

Synthesis of analogues of the iridolactones

Two stereoisomeric lactones of 2(2′-hydroxy-4′-methylcyclohex-1′-yl)propionic acid, analogues of the iridolactones, have been synthesized from -citronellal.     

Liquid chromatographic–electrospray mass spectrometric study of the phthalides of Angelica sinensis and chemical changes of Z-ligustilide

High-performance liquid chromatography–electrospray ionization–mass spectrometry has been applied to analyze the chemical constituents of Danggui (the rhizome of Angelica sinensis) and to study chemical changes of Z-ligustilide. Twelve phthalides were unambiguously identified as senkyunolide I (3), senkyunolide H (4), sedanenolide (8), butylphthalide (9), E-ligustilide (13), Z-ligustilide (14), Z-butylidenephthalide (15), Z,Z′-6.8′,7.3′-diligustilide (16), angelicide (17), levistolide A (18), Z-ligustilide dimer E-232 (19) and Z,Z′-3.3′,8.8′-diligustilide (20) in Danggui extract. The existence of 12 other phthalides (2, 5–7, 11, 12, 22–27), ferulic acid (1) and coniferyl ferulate (10) in Danggui extract has also been demonstrated. Phthalides 3, 4, 16–18 and 20 were determined to be the products from chemical change of Z-ligustilide. This is the first report of the existence of 16 compounds (2–8, 10–12, 20, 22–25 and 27) in Danggui extract.     

Synthesis of isotopically labeled puromycin derivatives for kinetic isotope effect analysis of ribosome catalyzed peptide bond formation

The mechanism by which the ribosome catalyze peptide bond formation remains controversial. Here we describe the synthesis of dinucleotides that can be used in kinetic isotope effect experiments to assess the transition state of ribosome catalyzed peptide bond formation. These substrates are the isotopically labeled dinucleotide cytidylyl-(3′-5′)-3′-amino-3′-deoxy-3′-l-phenylalanyl-N⁶,N⁶-dimethyladenosine (Cm⁶A_NPhe-NH₂) and cytidylyl-(3′-5′)-3′-amino-3′-deoxy-3′-(l-2-hydroxy-3-phenylpropionyl)-N⁶,N⁶-dimethyladenosine (Cm⁶A_NPhe-OH). These substrates are active in peptide bond formation and can be used to measure kinetic isotope effects in ribosome catalyzed protein synthesis.     

Facile synthesis of 2,2′-dichalcogenobis (N-alkyl/aryl benzenesulfonamides) from N-substituted benzenesulfonamides and the emergence of 2-alkyl 1,3,2-benzothiaselenazole 1,1 dioxides. Ebselen analogues

A one pot synthesis of 2-2′-diselenobis/ditellurobis(N-alkyl/aryl benzenesulfonamides) 4a-h from N-alkyl/aryl benzenesulfonamides is elaborated. The first cyclization of 2-2′-diselenobis (N-methyl benzenesulfonamide) 4a into 2- methyl-1,3,2-benzothiaselenazole 1,1 dioxide (5a)^1a using 3-chloroperoxybenzoic acid is described. Compounds 4a-h and 5a and d act as a new class of biologically active^1b compounds.     

Polyhydroxylated pyrrolizidines. Part 3: A new and short enantiospecific synthesis of (+)-hyacinthacine A2

(1R,2R,3R,7aR)-1,2-Dihydroxy-3-hydroxymethylpyrrolizidine (+)-Hyacinthacine A₂ 1 has been synthesized by Wittig's methodology using [(2′S,3′R,4′R,5′R)-3′,4′-dibenzyloxy-N-tert-butyloxycarbonyl-5′-tert-butyldiphenylsilyloxymethylpyrrolidin-2′-yl]carbaldehyde 3, prepared from a partially protected DMDP 2, and the appropriated ylide, followed by cyclization by an internal reductive amination process of the resulting unsaturated aldehyde 4 and total deprotection.     

Asymmetric synthesis catalyzed by chiral ferrocenylphosphine-transition metal complexes VII. New chiral ferrocenylphosphines with C2 symmetry

A new chiral ferrocenylphosphine ligand, 2,2′-bis[1-N,N-dimethylamino)ethyl]-1,1′-bis(diphenylphosphino)ferrocene (2), which has C₂ symmetry and a functional group on the side chain, was prepared by ortho-lithiation and phosphination of 1,1′-bis[1-N,N-dimethylamino)ethyl]ferrocene followed by optical resolution; recrystallization of the diammonium salt with tartaric acid. An X-ray diffraction study of PdCl₂[(+)-2] showed that the complex has square-planar geometry with two cis chlorine and two phosphorus atoms and ligand (+)-2 has an (S) configuration on the 1-dimethylaminoethyl side chain and (R) ferrocene planar chirality.     

X-ray crystal structure analysis and atomic charges of color former and developer: 2. Color formers

The crystal and molecular structures of 2′-amino-6′-dibutylamino-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (1), 2′-amino-6′-(N-cyclohexyl-N-methylamino)-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (2) and 2′-(2-chlorophenyl)amino-6′-dibutylaminospiro[isobenzofuran-1(3H), 9′[9H]xanthen-3-one (3) have been determined by single-crystal X-ray diffraction analysis. Atom-atom non-bonded potential energy and semiempirical quantum chemical calculations have been performed. The xanthene rings of 1 to 3 are slightly bent and the phthalide rings are planar. The phthalide ring moieties are almost perpendicular (88.9(1)−93.5(5)°) to the xanthene rings. The bond lengths C(6)---O(2) are apparently extended from the normal C(sp³)---O (lactone) length. The temperature factors for one butyl group C(32)---C(35)) of 1 increase gradually toward the terminal carbon. The temperature factors for C(30)---C(33) of 2 indicate large vibrations and these are reflected in short bond lengths. Two butyl groups of 3 are disordered and these C---C bond lengths are short and long alternately. Atomic net charges around spirocarbon C(6) and toward N(1) to C(6) indicate the weak alternative system in the colorless form. As the xanthene ring has a planar geometry, the π electron density migration will easily occur from the auxochromes attached to the phthalide ring to the xanthene ring.     

X-ray crystal structure analysis and atomic charges of color former and developer: 2. Color formers

The crystal and molecular structures of 2′-amino-6′-dibutylamino-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (1), 2′-amino-6′-(N-cyclohexyl-N-methylamino)-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (2) and 2′-(2-chlorophenyl)amino-6′-dibutylaminospiro[isobenzofuran-1(3H), 9′[9H]xanthen-3-one (3) have been determined by single-crystal X-ray diffraction analysis. Atom-atom non-bonded potential energy and semiempirical quantum chemical calculations have been performed. The xanthene rings of 1 to 3 are slightly bent and the phthalide rings are planar. The phthalide ring moieties are almost perpendicular (88.9(1)–93.5(5)°) to the xanthene rings. The bond lengths C(6)---O(2) are apparently extended from the normal C(sp³---O (lactone) length. The temperature factors for one butyl group C(32)---C(35)) of 1 increase gradually toward the terminal carbon. The temperature factors for C(30)---C(33) of 2 indicate large vibrations and these are reflected in short bond lengths. Two butyl groups of 3 are disordered and these C---C bond lengths are short and long alternately. Atomic net charges around spirocarbon C(6) and toward N(1) to C(6) indicate the weak alternative system in the colorless form. As the xanthene ring has a planar geometry, the π electron density migration will easily occur from the auxochromes attached to the phthalide ring to the xanthene ring.     

Photophysics of 6-(2′-hydroxy-4′-methoxyphenyl)-s-triazine photostabilizers

The room temperature photophysical properties of several sulphonated and unsulphonated 6-(2′-hydroxy-4′-methoxyphenyl)-s-triazines were investigated in a range of solvents by means of steady state and picosecond fluorescence spectroscopy. Compounds possessing phenyl or p-tolyl groups in the s-triazinyl ring exhibit only a very weak normal Stokes-shifted fluorescence, arising from the initially excited chromophore. Substitution of phenoxy groups into the s-triazinyl ring results in the appearance of an additional longer-wavelength fluorescence which is assigned to the keto tautomer, formed following excited state intramolecular proton transfer (ESIPT). The rate constant for the (ESIPT) process that occurs in sodium 3-(3′,5′-diphenoxy-2′,4′,6′-triazinyl)-4-hydroxy-2-methoxybenzene sulphonate in water is estimated to be greater than 10¹¹ s⁻¹.     

A new bibenzyl derivative from Pleione bulbocodioides

A new bibenzyl derivative 1, named 2-（4＇＇-hydroxybenzy1）-3-（3＇-hydroxyphenethy1）-5-methoxy-cyclohexa-2,5-diene-1,4- dione, and two known stilbenoids （2, 3） were isolated from the tubers of Pleione bulbocodioides （Franch.） Rolfe. Their structures were elucidated by spectroscopic methods.