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Two secoiridoid glucosides, lucidumosides A and B, as well as six known glucosides, oreoside dimethyl ester, ligustroside, oleuropein, nuezhenide, isonuezhenide, and neonuezhenide, were isolated from the fruits of Ligustrum lucidum. Their structures were elucidated by spectroscopic methods. (C) 2001 Elsevier Science Ltd. All rights reserved.

A simple convenient method has been developed for the preparation of N-acetyl-S-arylcysteines based on the Chan–Lam–Evans arylation of N,N′-diacetylcystine dimethyl ester with arylboronic acids and used to synthesize a series of arylmercapturic acids. Unlike copper-mediated N-arylation, the S-arylation of neither cysteine nor cystine derivatives proceeded satisfactorily in the presence of air.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Porphyrin–fullerene dyads with different linkages between the two subunits were synthesized for mimicking photosynthesis. NMR spectra and quantum mechanical calculations show special structural features that should influence light-induced electron transfer of the photosynthetic process. Starting point of the synthetic routes is a deuterioporphyrin dimethyl ester prepared from the readily accessible blood pigment heme. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The efficiency and validity of different chemical substrates for trapping bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene; 1) is dependent on the conditions of carbene generation. On conventional photolysis of dimethyldiazomalonate (=2-diazopropanedioic acid dimethyl ester; 2) by long-wave UV light (through a Pyrex filter, λ>290 nm), the most powerful trap for carbene 1 in the series of substrates Me2S, MeOH, cyclohexane, and pyridine is Me2S (with an efficiency ratio of ca. 6 : 4 : 2 : 1, resp.). When short-wave decomposition of diazomalonate 2 is employed (through a quartz filter, λ>210 nm), more reliable and useful chemical traps for bis(methoxycarbonyl)carbene (1) are pyridine and cyclohexane, whose adducts with 1 are rather stable under short-wave-irradiation conditions. Application of alcohols for the trapping of 1 proves to be preferential when simultaneous monitoring of carbene and oxoketene formation during photolysis is necessary.

The addition copolymerization of 5-norbornene-2-carboxylic acid methyl ester (NBCM) with norbornene (NB) catalyzed by CpNi-based (Cp = n 5 -C 5 H 5 ) systems, i.e., CpNi(PPh3)Me/B(C 6 F 5 ) 3 and CpNi(PPh3)Cl/AlMe 3 /B(C 6 F 5 ) 3 , was studied with particular focus on the reactivities of the endo- versus exo-isomers of NBCM. Unlike the well-known higher reactivity of the exo-isomer in Pd II -catalyzed polymerizations, the CpNi system showed a small but noticeable preference for the endo- isomer. The better reactivity of the endo-isomer is more pronounced in the copolymerization of cis-5-norbornene-2,3-dicarboxylic acid dimethyl ester (NBCD) with NB, where only the endo-isomer gave the copolymer when the NB/NBCD feed ratio was 6/4.

The thermal decarboxylative cycloaddition of the title compound and its dimethyl ester with vinyl acetates (I) and (IV) or alkynyls (IX) and (XI) follows Diels-Alder methodology.

Three new urea derivatives, isolated from the Pliocene lignified wood of Pinus armandii, were identified as carbonylbis[imino(6-methyl-3,1-phenylene)]bis[carbamic acid] dimethyl ester (1), and as the corresponding dibutyl ester 2 and bis(2-methylpropyl) ester 3. Their structures were elucidated by spectroscopic methods, including MS and 1D- and 2D-NMR techniques.

Acid-promoted esterification of Thiele's acid with methanol was found to afford three products. In addition to the expected major product (i.e. the corresponding dimethyl ester, 2a), two minor products are obtained, one of which, 3, results from subsequent Michael addition of methanol to the norbornene CC double bond in 2a. Analysis of its one- and two-dimensional NMR spectra indicates that this minor product possesses structure 3a in which the (C-5)—OCH3 and (C-6)—CO2CH3 bonds are exo and endo, respectively. This conclusion is reinforced by the results of thermodynamics calculations and associated chemical shift calculations. In addition, theoretical analysis of competing transition states for Michael addition of methanol to 2a suggests that exo approach of methanol towards the (C-5)(C-6) double bond in the substrate is preferred kinetically over the corresponding endo reaction pathway. Copyright © 2004 John Wiley & Sons, Ltd.

A simple route for synthesis of new tetrathiafulvalene dimethyl ester (TTF-DME) is reported. The tetrathifulvalene dimethylester (TTF-DME) has been prepared by introducing an ester coordination function as a bifunctional new donor. The redox behavior of the TTF-DME was investigated in comparison to the well-known dibenzotetrathiafulvene (DB-TTF) by cyclic voltammetry. A two-electron redox behavior was observed as a two waves.

Steroselective Synthesis of the Nitrite-Reducing Cofactor Heme d1 from Hematoporphyrin The nitrite-reducing cofactor heme d1 has been synthesized in a few synthetic steps, starting from readily accessible hematoporphrin dimethyl ester (rac-4a). A single-crystal structure analysis of the synthesized target molecule rac-10a unequivocally established the constitution and the relative configuration of heme d1 (3).

A series of 14 4-(3′,5′-disubstituted isoxazolyl)-1,4-dihydropyridine calcium channel antagonists were examined using variable-temperature proton nuclear magnetic resonance spectroscopy and nuclear Overhauser effect (NOE) experiments. Two of these compounds, the 1,4-dihydro-2,6-dimethyl-4-[5′-methyl-3′-(4″-fluorophenyl)isoxazol-4′-yl]-3,5-pyridinedicarboxylic acid dimethyl ester (3a) and 1,4-dihydro-2,6-dimethyl-4-[5′-methyl-3′-(4″-bromophenyl)isoxazol-4′-yl]-3,5-pyridinedicarboxylic acid dimethyl ester (5a), were synthesized to assist in the clarification of ambiguities discovered in the low-temperature spectra of 1,4-dihydro-2,6-dimethyl-4-(5′-methyl-3′-phenylisoxazol-4′yl)-3,5-pyridinedicarboxylic acid diethyl ester (2b). The solid-state structure of 3a is also reported. The solution-state rotameric preferences of the 14 compounds are reported and compared with those calculated at the AM1 level. C-4—C-4′ bond rotation barriers were also calculated at the AM1 level for nine of the systems examined. Several species failed to display temperature-dependent signals associated with hindered rotation owing to highly biased rotameric equilibria at the temperatures required to freeze out the rotation. The seven experimental rotation barriers (ΔG≠ from ⩽26 to 40.4 kJ mol−1) reported are 1–6.8 kJ mol−1 higher than ΔH≠ calculated at the AM1 level.

Chemical investigation of the ethanolic extract of Jasminum polyanthum Franch has resulted in the isolation of verbascoside (10) and 9 secoiridoid glycosides including oleoside dimethyl ester (1), 10-hydroxy oleoside dimethyl ester (2), oleoside 11 methyl ester (3), methyl-glucooleoside (4), 8-epikingiside (5), ligustroside (6), angustifolioside B (7), oleuropein (8), and oleoacetoside (9). The structures of 1-10 were established primarily on the basis of NMR analysis.

Cyclic nitrones regioselectively add to Feist′s acid dimethyl ester (II) yielding diastereoisomeric mixtures of isoxazolidines which are susceptible to thermal rearrangement reactions.

Reaction of N-benzylideneaniline, 1a, with 3-methyl-2-oxobutanedioic acid diethyl ester, 2a, produced isomeric 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid ethyl esters, 3a and 3b. The higher melting isomer, 3a, was shown to have the (Z) configuration by nmr spectroscopy. The (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic acid methyl esters, 3c and 3d, were prepared from 1a and 3-methyl-2-oxobutanedioic acid dimethyl ester, 2b. The higher melting isomer, 3c, was shown to have the (Z) configuration. Similarly, N-benzylidene-p-toluidine, 1b, reacted with 2a to form (Z) and (E) isomers of 3-methyl-4,5-dioxo-1-(4-methylphenyl)-2-phenyl-3-pyrrolidinecarboxlic acid ethyl esters, 3e and 3f. Assignment of the 13C carbonyl carbon nmr chemical shift was made by preparing 2-methyl-3-oxobutanedioic-1-13C acid diethyl ester, 4, and from it the corresponding (Z) and (E) isomers of 3-methyl-4,5-dioxo-1,2-diphenyl-3-pyrrolidinecarboxylic 13C acid ester, 5a and 5b. The mass spectra of the (Z) isomers exhibit prominent ions corresponding to the masses of the Schiff bases used to make them, and ions corresponding to the loss of ArNCOCO from the parent ion. The (E) isomers 3b, 3d and 5b exhibit a prominent ion of mass 264; 3f gives mass 278, corresponding to the loss of the carboalkoxy group.

N-Arylsulfonyl carbonimidodithioic acid dimethyl ester has been reacted with nitroalkanes to generate the corresponding 1-alkylthio-1-aryl sulfonamido-2-nitroethylenes; the latter have been hydrolysed to N-arylsulfonyl-2-nitro-acetamides. Solvent dependent imine-enamine tautomerism is observed in the nitroenamines 2a-d.

The reaction of 5-(p-toluenesulfonyl)-3,4-disubstituted Δ3-pyrrolin-2-one with aldehydes in the presence of tributylphosphine and 1,8-diazabicyclo[5.3.0]undec-7-ene gave the corresponding 5-exomethylene compounds in good yields. A pyrromethenone derivative as a potential equivalent to C/D ring component of phytochromobilin dimethyl ester was effectively prepared by means of the present method.

The structure of the major dibenzofuran present in the lichen Leproloma diffusum has been shown to be that of 4-oxypannaric acid 2-methyl ester (2-methyl hydrogen 3,4,9-trihydroxy-1,7-dimethyldibenzofuran-2,6-dicarboxylate) (2). The structure of (2) was confirmed by total synthesis, achieved through a biomimetic-type approach using palladium(II) acetate in the key cyclization step. Partial synthesis of the corresponding dimethyl ester (8) was effected starting from natural pannaric acid 6-methyl ester (6).

The title amino acid derivative has been synthesized stereoselectivety in 40% overall yield from 5-tert-butyldiphenylsilyloxymethyl-2(5H)-furanone used as a chiral precursor.

Chemical synthesis of a trachylobagibberellin analogue - 3-hydroxy- δ1.10−12, 16-cyclogibberellin dimethyl ester 4 from gibberellin acid GA3 3 was described herein. The key step is the decomposition of the tosylhydrazone 11 to construct the novel [3.2.1.0.2.7] octane system.

10-Deaza modifications of classical antifolate analogues bearing the 1,4-disubstituted naphthalene ring in place of the 1,4-disubstituted benzene ring were prepared and tested for antitumor activity. Naphthalene analogues (9a−c, respectively) of 10-deazaaminopterin, 5-methyl-5,10-dideazaaminopterin, and 5-ethyl-5,10-dideazaaminopterin were prepared by a route consisting of C-alkylations of the anion derived from 4-carboxy-1-naphthaleneacetic acid dimethyl ester (2) by 6-(bromomethyl)-2,4-diaminopteridine (1a) and 6-(bromomethyl)-2,4-diamino-5-methyl- and -5-ethyl-5-deazapteridines (1b and 1c, respectively) followed by ester hydrolysis and subsequent decarboxylation to give naphthalene analogues (7a−c, respectively) of 4-amino-4-deoxy-10-deazapteroic acid and 4-amino-4-deoxy-5-methyl- and -5-ethyl-5,10-dideazapteroic acids. Peptide coupling of 7a−c with l-glutamic acid dialkyl ester followed by mild ester hydrolysis gave target compounds 9a−c. The key advantage of this route is circumvention of a hydrogena...

A new secoiridoid glucoside, jaspolyside was isolated from the leaves of Jasminum polyanthum along with nine known secoiridoid glycosides: oleoside dimethyl ester, 10-hydroxyoleoside dimethyl ester, oleoside 11-methyl ester, methyl-glucooleoside, 8-epi-kingiside, ligustroside, angustifolioside B, oleuropein, and oleoacetoside. The structure of the new compound has been established on the basis of spectral and chemical methods.

Perfectly branched polyamide dendrons based on 5-(2-aminoethoxy)-isophthalic acid have been synthesized up to generation 4 following the convergent approach. This involved a repetitive reaction of 5-(2-t-butoxycarbamylethoxy)-isophthalic acid with the two fold excess of 5-(2-aminoethoxy-hydrochloride)-isophthalic acid dimethyl ester and its analogs of higher generation, respectively, using activation and protection methods from the peptide chemistry. The products were characterized via elemental analysis, different spectroscopic methods, gel permeation chromatograpy, and differential scanning calorimetry.

Antimalarial drug artemisinin and haemin react in vitro, to give a δ-meso hydroxy porphyrin isolated as a stable dimethyl esterified zinc complex and characterised as (20-hydroxyprotoporphyrinato dimethyl ester)zinc(II) by NOESY, visible absorption and ESI-MS; the structure sheds light on the mechanism of action of endoperoxide antimalarials.

Chiral ligands with achiral backbones such as ethano- or ferroceno-bridges linking two phosphonites derived from chiral diols such as binaphthol (BINOL) have been prepared; the corresponding Rh complexes are excellent catalysts in the hydrogenation of prochiral olefins such as itaconic acid dimethyl ester or 2-acetamido methyl acrylate, the ee values being 90–99.5%.

Phytochemical investigation of the dried leaves of Jasminum officinale var. grandiflorum has led to the isolation of two new secoiridoid glucosides, (2"R)-2"-methoxyoleuropein and (2"S)-2"-methoxyoleuropein, together with four known secoiridoid glucosides, oleuropein, ligstroside, demethyloleuropein and oleoside dimethyl ester, a lignan, (-)-olivil and p-hydroxyphenethyl alcohol. The structures of the new compounds were elucidated from chemical and spectroscopic evidence.

Simple and efficient synthesis of several new 1,3,7-trisubstituted bicyclo[3.3.1]nonane derivatives [e.g. 1-hydroxybicyclo[3.3.1]nonane-3,7-dicarboxylic acid (4), dimethyl ester 1-hydroxybicyclo[3.3.1]nonane-3,7-dicarboxylic acid (5), di-methyl ester-1-methoxybicyclo[3.3.1]nonane-3,7-dicarboxylic acid (5a), 1-hydroxy-3,7-di(hydroxymethyl)bicyclo[3.3.1]nonane (6), 1-hydroxy-3,7-di(bromomethyl)bicyclo[3.3.1]nonane (7), 1-bromo-3,7-di(bromomethyl)bicyclo[3.3.1]nonane (8) and 1-bromo-3,7-di(cyanomethyl)bicyclo[3.3.1]nonane (9)] is described.

(RS)-1 (85% ee) was prepared by utilizing a porcin pancreatic lipase-promoted hydrolysis of sulfinyldiacetic acid dimethyl ester (8) which was derived from thiodiacetic acid (7). (RS)-1 (99% ee) and (SS)-1 (99% ee) were readily obtained by methanolysis of (RS,S)-12 and (SS,S)-12 with MeONa in MeOH. (RS,S)-12 and (SS,S)-12 were furnished by chromatographic separation of the diastereomeric mixture, obtained by oxidation of thiodiacetic mono-carboxylic acid (11) with 30% H2O2 followed by dehydrative condensation of the resultant sulfinyldiacetic mono-carboxylic acid with 4(S)-isopropyl-1,3-thiazolidine-2-thione. (RS)-1 (99% ee) was successively treated with (TMS)2NLi, Ac2O, and TMSOTf to give a major chiral-3 product in 75% ee and in a highly chemoselective manner (chiral-3 : chiral-2=93 : 7).

It is demonstrated that the dimethyl ester of 1,2-di (methoxycarbonyl) ethane phosphonic acid can be used as a phosphorylating agent of the production wastes of dimethyl terephthalate. The products obtained have different characteristics depending on themode of phosphorylation

Total Synthesis of (±)-Bonellin Dimethyl Ester Bonellin (1) is the green sex-differentiating pigment of Bonellia viridis, a marine animal widely distributed in the Mediterranean Sea. Bonellin dimethyl ester (rac-2), has been synthesized from the four monocyclic building blocks 6, 7, 8b, 10 and the selectively cleavable malonic ester 9 by an highly convergent synthetic concept.

An easy synthetic approach to glycoporphyrins from zinc(II)-2-vinyl-5,10,15,20-tetraphenylporphyrin or zinc(II)-proto-porphyrin-IX dimethyl ester and O-allyl carbohydrate acetonides by cross-metathesis is reported.

Dimethyl aminomalonates were electrochemically oxidized in methanol to afford the corresponding cyclization products through the formation of carbon-carbon bonds. Optimum yields were obtained when NaCN was utilized as the supporting electrolyte at room temperature. Presumably, the electrooxidation involves a two-electron oxidation process.

1-Methylenphosphonate-1-deoxy-L-idonojirimycin (1) has been synthesized starting from commercially available tetrabenzyl glucose, the key steps being substitution of the hydroxyl group at C-5 of compound 7 with an azido group, stereoselective reaction of the aldehyde at C-1 of compound 10 with dimethyl methylenephosphonate anion, conversion of the azide into an amino group, and finally cyclization of the aminoalcohol 12. [GRAPHICS]

A series of EWG-substituted primary ketene N,O-acetals were reacted with tetrazine-3,6-dicarboxylate yielding, by [4+2] cycloaddition, tetrafunctionalized pyridazines, which possess an EWG group, a primary amino function and two ester moieties. Reductive ring contraction of pyridazines gave aminopyrrole derivatives. Treatment of cyanamide with tetrazine-3,6-dicarboxylate led to a 5-amino-1,2,4-triazine derivative, which was rearranged to 4-aminoimidazole-2,5-dicarboxylic acid dimethyl ester.

Reactions of cyclopentanonopimaric acid dimethyl ester with phosphoryl chloride, ethyl formate, and p-nitrobenzaldehyde afforded Δ1 5 ( 1 6 )-16-formyl-15-chloro, 16-hydroxymethylene-15-oxo, and 16-nitrobenzylidene-15-oxo derivatives which were subjected to heterocyclizations to obtain new diterpene pyrimidine, pyrazole, and oxazole derivatives.

[reaction: see text] In the reaction of arylaldehydes or N-sulfonated imines (0.5 mmol) with dimethyl acetylenedicarboxylate (DMAD) (0.6 mmol) catalyzed by pyridine or DMAP (20 mol %), we found that (E)-2-aryl-but-2-enedioic acid dimethyl ester 1 or (E)-2-[aryl-(toluene-4-sulfonylimino)methyl]-but-2-enedioic acid dimethyl ester 2 was formed in good yields at 60 degrees C in THF. A plausible mechanism has been proposed.

A first direct nitration of C—H bond of cubane-1,4-dicarboxylic acid dimethyl ester by dinitrogen tetraoxide at ∼20 °C has been carried out. During the nitration no rearrangement of cubane skeleton has been observed.

Gas-liquid chromatography was used to establish that the reactivity of the cis isomer in the reaction of 5-isopropyl-4-methyl-1,3-dioxane with the diisobutyl ester of isobutylboric acid leading to the corresponding 1,3,2-dioxaborinane is greater than for the trans isomer. An AM1 calculation for the energy of the intermediate ions in this reaction with model derivatives of boric acids: dioxyborane and the dimethyl ester of methylboric acid showed that one of the probable reasons for the observed behavior is the lower barrier for conversion of the intermediate bipolar structure of the cis derivative in the step involving formation of the endocyclic B-O bond.

A convenient and stereoselective synthetic route to the precursor of natural products, lignans, containing tetrahydrofuran has been developed. A series of asymmetric 2-aryltetrahydrofuran-3,4-carboxylic acid derivatives were synthesized in high yields with this route. The effect of substituents on the Diels-Alder reaction of aryl-substituted oxazoles with alkyne dienophile and on the catalytic hydrogenation of dimethyl 2-arylfuran-3,4-dicarboxylates has been investigated. The regioselective hydrolyses of the dimethyl ester group was also studied. All products were characterized by elemental analysis, FT-IR, 1H NMR and MS.