bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese und Charakterisierung von β‐phosphoranalogen Asparaginsäure‐Derivaten: 2‐Amino‐3‐aryl‐3‐phosphorylpropionsäure‐Derivate
Authors: Preußler Carola , Schnepp Kathrin , Kellner Kurt
Published: July 2007

Synthesis and Characterization of β‐Phosphorus Analogues of Aspartic Acid Derivatives: 2‐Amino‐3‐aryl‐3‐phosphorylpropionic Acid Derivatives

The 4‐benzylidene‐4,5‐dihydro‐5‐oxazolones 1 react with alkali dialkyl phosphites 2 to give the alkali salts of 4‐[(dialkoxyphosphoryl)methyl]‐5‐hydroxyoxazoles 3. Silylation of 3 with ClSiMe3 yields the 5‐siloxyoxazole derivatives 4. Treatment of 4 with alcohols or water provides 3‐aryl‐2‐(benzoylamino)‐3‐(dialkoxyphosphoryl)propionic acid esters 6 and propionic acids 7, respectively. The ratio of the diastereomeres of 6 (A, B) and 7 (A, B) depends on the reaction conditions. A remarkable different diasteroselectivity is observed in basic versus acidic media. The proposed reaction pathway is supported by characterization of the intermediate 4‐[(dialkoxyphosphoryl)methyl]‐4,5‐dihydro‐5‐oxazolone 8. A complete hydrolysis of compounds 6 produces the 3‐phosphonoaspartic acid 9.
Polymorphie an chiralen phosphoranalogen Asparaginsäure‐Derivaten: Kristall‐ und Molekülstruktur von 2‐(Benzoylamino)‐3‐(diethoxyphosphoryl)‐3‐(4‐methoxyphenyl)propionsäure‐methylester
Authors: Preußler Carola , Kellner Kurt , Sieler Joachim
Published: July 2007

Polymorphy on Chiral Phosphorus Analogues of Aspartic Acid Derivatives: Crystal and Molecular Structure of Methyl 2‐(Benzoylamino)‐3‐(diethoxyphosphoryl)‐3‐(4‐methoxyphenyl)propionate

The diastereomers of the title compound 1 were characterized by X‐ray structure analyses. The relative configuration of diastereomer A is determined as RS/SR, diastereomer B shows RR/SS configuration. Depending on the different configurations hydrogen bonds are formed by the phosphoryl oxygen with the amide hydrogen intermolecularly (form A) or intramolecularly (B). No interaction is observed of the carboxylate and the amide oxygen, respectively, with the amide hydrogen.
Endogenous alkaloids in man, IX. Potential tryptophan‐derived alkaloids in chloral‐treated patients: Synthesis and stereostructure
Authors: Bringmann Gerhard , Hille Annette , Stäblein Michaela , Peters Karl , Von Schnering Hans Georg
Published: July 2007

The trichlorotetrahydroharmancarboxylic acids 5a and 5b were shown to be formed in aqueous medium under neutral, physiological conditions from the amino acid tryptophan and the nonnatural aldehyde chloral. Preparative diastereomer resolution and configurational analysis were performed via the methyl esters 7a/7b. The structure of 7b was proved by an X‐ray structural analysis. By cautious hydrolysis, the chloral‐derived potential „mammalian alkaloids”︁ 5a and 5b were obtained in analytically pure form.
Stereoselective synthesis of alcohols, XL. Stereoselective cyclization of 7‐oxo‐2‐heptenylboronates
Authors: Hoffmann Reinhard W. , Niel Gilles
Published: July 2007

Intramolecular allylboration reaction of 7‐oxo‐2‐heptenyl boronates leads to 2‐vinylcyclopentanols. The cyclization proceeds in a stereospecific manner, such that the (E)‐allylboronate 8 is converted into trans‐2‐vinylcyclopentanol (2) and the (Z)‐allylboronate 10 into cis‐2‐vinylcyclopentanol (3). Asymmetric induction originating from stereogenic centers placed between the boronate and the aldehyde function has been found to be low.
Stereoselective synthesis of alcohols, XLI. Chirality transfer to generate quaternary stereogenic centers by an allylboration reaction
Authors: Hoffmann Reinhard W. , Schlapbach Achim
Published: July 2007

The acyclic alcohols 13 and 14 having a neighboring quaternary stereogenic center can be obtained in diastereoselectivities of > 95% by addition of the ß,γ,γ‐trisubstituted allylboronates 12 to aldehydes. Starting from the nonracemic allylboronates 19 of presumed 84–92% e.e., we have obtained the alcohols 13a and 14a with the corresponding levels of the e.e.
Asymmetric Syntheses via Heterocyclic Intermediates, XLV. Asymmetric Synthesis of Diastereomerically and Enantiomerically Pure 3‐Substituted (2R,3S)‐serine Methyl Esters
Authors: Beulshausen Tessa , Groth Ulrich , Schöllkopf Ulrich
Published: July 2007

The titanium derivative 2 of the bislactim ether 1 of cyclo(‐L‐Val‐Gly‐) reacts with aldehydes and ketones 3 highly diastereoselectively to give the syn‐addition products 4. Upon hydrolysis with diluted trifluoroacetic acid the compounds 4 yield besides methyl L‐valinate the (2R,3S)‐threo‐serine methyl esters 5.
Heterocyclization with iminium chlorides, V. Condensation of 1,3‐dichlorotrimethinecyanines with 1,3‐ and 1,2‐dinucleophiles
Authors: Tóth Gábor , Kovács Attila , Bitter István , Duddeck Helmut
Published: July 2007

Cyclic 1,3‐dichlorotrimethinecyanines 1 were used for the preparation of condensed polycycles 2–13 with high regioselectivity. In the case of five‐membered cyanines the exclusive formation of the linear‐type products was observed, while with six‐ and seven‐membered cyanines the linear or angular type of products were obtained, depending on the character of the nucleophile. The structures of the products were supported by 1H‐, 13C‐ and 15N‐NMR data, NOE difference spectroscopy, and different two‐dimensional carbon‐proton correlation measurements.
Unexpected transformations of camphor (thio)semicarbazones under acetylating conditions
Authors: Somogyi László
Published: July 2007

The formation of camphor mono‐ and diacetylhydrazones (1, 4, 6) and a stereoselective synthesis of the spirothiadiazoline (1R)‐(+)‐2 is described. The degradation of (thio)semicarbazones 3 (X = O, S) and diacetylhydrazone 4 to the acetylhydrazone 6 has been performed.
Reactions of 3‐acyl‐substituted 2H‐1‐benzopyran‐2‐ones with acid anhydrides, II
Authors: Bojilova Anka , Rodios Nestor , Nicolova Rositsa , Ivanov Christo
Published: July 2007

3‐Pivaloyl‐2H‐1‐benzopyran‐2‐one (6) reacts with acid anhydrides in the presence of triethylamine to give 4‐(2‐oxoalkyl)‐2‐oxochromans 7 and 3‐pivaloyl‐2‐oxochroman (8) in moderate yields. Also 3‐propionyl‐ and 3‐isobutyryl‐2H‐1‐benzopyran‐2‐ones (9) react with acid anhydrides under the same reaction conditions to give 4‐(2‐oxoalkyl)‐2‐oxochromans 10 and pyrano[3,4‐c][2H]chromenes 11 as the main products. A mechanistic explanation for the formation of these compounds is proposed.
Thermal Degradation of Glycosides, IV. Degradation of flavonoid glycosides
Authors: Kim Youn Chul , Higuchi Ryuichi , Kitamura Yoichi , Komori Tetsuya
Published: July 2007

By mere heating, the flavone (1, 7), flavanone (4, 10), and flavonol glycosides (13, 14) are converted into their aglycones and monoglycosides. The products of pyrolysis have been isolated by chromatography and their structures elucidated by chemical and spectroscopic methods. The compound derived from the sugar moiety in the pyrolysis of glucosides has been identified as levoglucosan (17). From the structures of some minor products (16, 18, 19), generated by the thermal degradation, a mechanism of their generation and the elucidation of the structures of rearranged ions (for example [M + 146 + H]+), often generated in the FD‐mass spectra of glycosides, are presented.
An improved synthesis of bicyclo[3.3.0]octane‐2,6‐dione
Authors: Quast Helmut , Janiak Rolf
Published: July 2007

The Michael addition of dimethyl malonate (12) to tert‐butyl acrylate (11), carried out without solvent, affords the triester 13a in 88% yield on a kg scale. Selective partial hydrolysis of 13a produces the monoacid 13b almost quantitatively. The Kolbe electrolysis of 13b furnishes the tetraester 7c as a crystalline 1:1 mixture of diastereomers in 62–74% yield. The Dieckmann condensation of 7c is induced by sodium hydride/tert‐butyl alcohol in tetrahydrofuran and yields the enolized β‐oxo ester 8c which, on acidic hydrolysis followed by decarboxylation, produces the title diketone 2 in 90% yield, based on 7c. Thus, the useful diketone 2 is obtained in 46–55% overall yield on a 100‐g scale.
Synthesis of Sphingosine Relatives, XI. Synthesis of wheat grain cerebroside with fruiting‐inducing effect on Schizophyllum commune
Authors: Mori Kenji , Kinsho Takeshi
Published: July 2007

(2S,3R,8Z)‐1‐O‐(β‐D‐Glucopyranosyl)‐N‐hexadecanoyl‐8‐sphingenine (1) and its (8E) isomer 1(E) were synthesized by starting from D‐(−)‐tartaric acid.
Aminosäureester als chirale Hilfsgruppen bei Barbier‐Reaktionen in wäßriger Lösung
Authors: Waldmann Herbert
Published: July 2007

Amino Acid Esters as Chiral Auxiliaries in Barbier‐Type Reactions in Aqueous Solution

Valine and proline benzyl ester are converted into the aliphatic and aromatic α‐oxo amides 5 by activation of the respective α‐oxo acid by means of N,N′‐diisopropylcarbodiimide. The α‐oxo amides 5 undergo Barbier‐type reactions with differently substituted allyl halides in the presence of zinc and pyridinium toluenesulfonate in water/THF (2:1, v/v) at 4°C. Thereby, the α‐hydroxy amides 8/9 are formed in high yields and, in the case of the proline ester amides, with diastereomer ratios of 4–6:1. In the absence of any allyl halide, or if the addition of the allyl moiety to the carbonyl groups is only slow, the oxo groups are reduced to secondary alcohols, thus giving rise to the α‐hydroxy amides 12/13. During the reduction of the pyruvamide 5d also the competitive formation of the pinacol adduct 15 is observed. These results indicate that in the Barbier reactions in aqueous solution radicals are involved as intermediates.
Synthesis of the 4‐Pyridine Analog of Kostanecki's Triketone. Determination of Constitution and Stereochemistry by 2D‐NMR Spectroscopy and X‐ray Structural Analysis
Authors: Kessler Horst , Mronga Siggi , Kutscher Bernhard , Müller Arndt , Sheldrick William S.
Published: July 2007

4‐Acetylpyridine reacts stereoselectively with benzaldehyde under basic conditions to afford rac‐1. The constitution of 1 was determined by the long‐range connectivities revealed by the H, C‐COLOC spectrum. The relative stereochemistry of the chiral centers C‐2 to C‐6 was obtained from 3JHH couplings. The stereochemistry at the non‐proton bearing C‐1 was established by through‐space connectivities from ROESY and semiquantitative analysis of 3JCH from an inverse 2D‐NMR spectrum (HMBC). The NMR findings were confirmed by single crystal X‐ray diffraction.
An expedient synthesis of rac‐2,3‐di‐O‐stearoyl‐1‐thiophosphatidylcholine via thiophosphatidic acid diesters
Authors: Młotkowska Barbara
Published: July 2007

A convenient triester approach to rac‐2,3‐di‐O‐stearoyl‐1‐thiophosphatidylcholine (7) involving the preparation of S‐[2,3‐bis(stearoyloxy)propyl] O‐(2,4‐dichlorophenyl) O‐methyl thiophosphate (4) followed by demethylation, coupling of the resulting salt 5 with choline 2‐mesitylenesulfonate and subsequent removal of 2,4‐dichlorophenyl protecting group is described.
Hexafluoraceton als Schutzgruppen‐ und Aktivierungsreagenz in der Aminosäure‐ und Peptidchemie, 7. Synthese von γ‐Oxo‐α‐aminosäure‐Derivaten aus Asparaginsäure
Authors: Burger Klaus , Rudolph Martin , Neuhauser Horst
Published: July 2007

Hexafluoroacetone as Protecting Group and Activation Reagent in Amino Acid and Peptide Chemistry, 7. – Synthesis of γ‐Oxo α‐Amino Acid Derivatives from Aspartic Acid

Optically pure γ‐oxo α‐amino acids are obtained on reaction of acid chloride 2 with aromatic and heteroaromatic compounds under Friedel‐Crafts conditions.
Products from furans, 13. Synthesis of 6‐acyloxy and 6‐alkoxy derivatives of 2H‐pyran‐3(6H)‐ones
Authors: Constantinou‐Kokotou Violetta , Kokotos George , Georgiadis Minas P.
Published: July 2007

The 6‐hydroxy‐2H‐pyran‐3(6H)‐ones 1a–d are esterified stereoselectively with acetic and formic acid, and with several amino acids and peptide derivatives using the DCC/DMAP method. The direct synthesis of the 6‐alkoxy derivatives 3g–k is also studied.
Synthesis of α‐amino phosphonic acids via oxoiminium salts
Authors: Shatzmiller Shimon , Dolitzky Ben‐Zion , Meirovich Revital , Neidlein Richard , Weik Christian
Published: July 2007

The oxoiminium salts 4a, b, and 8 obtained by alkylation with Et3OBF4 of the aldonitrones 3a, b, and 7 react with diphenyl hydrogen phosphite to give the N‐alkoxy α‐amino phosphonic esters 6 and 9a, b. Similarly, the cyclic imine oxides 10a, b and the cyclic oxime ethers 14a, b afford the α‐branched N‐alkoxy α‐amino phosphonic esters 12a, b and 16a, b, respectively. Hydrogenolysis and ester hydrolysis affords the α‐methyl α‐amino phosphonic acid hydrochlorides 13a, b and 17a, b.
Synthesis of β‐lactosyl 1‐thioceramide
Authors: Bär Thomas , Schmidt Richard R.
Published: July 2007

3‐O‐Benzoyl‐azidosphingosine 3 was transformed into the corresponding 1‐thio derivative 6. Its sodium sulfide salt 6A was treated with hepta‐O‐acetyl‐α‐lactosyl bromide 8 to provide after complete O‐deprotection the β‐connected thioglycoside 9. Azido group reduction and N‐palmitoylation led to the desired β‐lactosyl thioceramide 1; for structural assignments it was converted into the per‐O‐acetyl derivative 2.
Geometrically directed lithiation of O‐Alkyloximes for the synthesis of linear polyethers
Authors: Shatzmiller Shimon , Dolitzki Ben‐Zion
Published: July 2007

For synthetic purposes, the polyether‐based secondary alcohols 7 and 8 were prepared from acetone O‐methyloxime (1). This applies the (Z) effect for the geometry‐directed alkylation sequence, recovery of the keto group and reduction. In contrast to 11, α‐phenylthio‐substituted O‐alkyloxime 26 was found to be unsuitable as starting material for such synthesis. The strong effect of bivalent sulfur in the α‐position shadows the (Z) effect and permits only lithiation next to the sulfur atom.
Inter‐ and intramolecular hetero‐Diels‐Alder reactions, 37. Syntheses of the 3‐amino sugar glycosides rac‐4‐deoxydaunosaminide rac‐4‐deoxyristosaminide, and rac‐acosaminide
Authors: Tietze Lutz F. , Hartfiel Uwe , Hübsch Thomas , Voß Edgar , Bogdanowicz‐Szwed Krystyna , Wichmann Jürgen
Published: July 2007

The hetero‐Diels‐Alder reaction of the phenylthio‐activated N‐monoacyl‐ and N,N‐diacyl‐enamino ketones 8a‐c containing a methyl group at position 2 of the oxadiene with the electron‐rich dienophiles 9a‐c yields the exo/endo adducts 10a‐d and 11a‐d in 82–95% yield with the endo adducts as the main products. The enamino ketone 8d with a S‐ethyl group at C‐3 does not react. Hydrogenation of 11a with Raney nickel in THF leads to the desulfurized dihydropyran 12, whereas in MeOH gives stereoselectively the perhydrophthalimido derivative 13, which, after deprotection, yields the β‐methyl glycoside 14 of rac‐4‐deoxydaunosamine. Under similar conditions 10c is converted into the β‐ethyl glycoside 15 of rac‐N‐benzoyl‐4‐deoxyristosamine. Stereoselective hydroboration of 12 affords 17 and subsequent cleavage of the protecting group leads to the β‐methyl glycoside 18 of rac‐acosamine.
Diastereomeric 5,6‐dimethyl‐4H‐1,3‐dioxin‐4‐ones from (−)‐(1R,4S)‐menthone: Synthesis and NMR analysis
Authors: Jansen Ursula , Runsink Jan , Mattay Jochen
Published: July 2007

The two diastereomers of spirocyclic 5,6‐dimethyl‐4H‐1,3‐dioxin‐4‐one (5, 6) have been synthesized by acetalization of tert‐butyl 2‐methyl‐3‐oxobutanoate (2) with (−)‐menthone (4). Their structures have been determined by NMR analysis.
Pyrazino[2,3‐c]‐1,2,6‐thiadiazine 2,2‐dioxides. Synthesis of SO2 analogues of folic acid antagonists
Authors: Alkorta Ibon , Goya Pilar , Páez Juan Antonio , Pérez Concepción
Published: July 2007

The synthesis of novel analogues of foric acid (FA) antagonists derived from the pyrazino[2,3‐c]‐1,2,6‐thiadiazine 2,2‐dioxide system incorporating the glutamic acid side chain at the 7‐position is described. No significant DHFR inhibition of cytotoxic activity has been found with these compounds.
Synthese und Stereochemie von 4‐Thiazolidinylphosphonsäureestern
Authors: Martens Jürgen , Kintscher Jürgen , Lindner Karen , Pohl Siegfried , Saak Wolfgang , Haase Detlev
Published: July 2007

Synthesis and Stereochemistry of Dimethyl 4‐Thiazolidinylphosphonates

Dimethyl phosphite adds to the azomethine bond of 2,5‐dihydrothiazoles 1 to produce dimethyl 4‐thiazolidinylphosphonates 2. Depending on the reaction conditions diastereomeric mixtures 2 are formed and explained by a two‐step mechanism. Assignment of configurations is proved by an X‐ray structure analysis of the thermodynamically more stable stereoisomer of 2c. N‐Acylated derivatives 5 could not be obtained by direct acylation of 2 but by a TiCl4‐catalyzed Michaelis‐Arbusov‐type reaction of trimethyl phosphite with N‐acyl‐4‐methoxythiazolidines 3. Phosphonates 5 are formed with high diastereoselectivity.
Über Pyridinium‐N‐phenolat‐Betaine und ihre Verwendung zur Charakterisierung der Polarität von Lösungsmitteln, XVI. Bestimmung der empirischen Lösungsmittelpolaritäts‐Parameter ET(30) und AN für 55 substituierte Phenole
Authors: Spange Stefan , Lauterbach Manfred , Gyra Anett‐Kathrin , Reichardt Christian
Published: July 2007

Pyridinium N‐Phenoxide Betaines and Their Application for the Characterization of Solvent Polarities, XVI1). – Determination of the Empirical Parameters of Solvent Polarity ET(30) and AN for 55 Substituted Phenols

By means of the negatively solvatochromic dyes 1 and 2, the empirical solvent polarity parameters ET(30) and AN (Acceptor Number) are determined for solutions of 55 substituted phenols in 1,2‐dichloroethane as inert solvent (Table 1). The ET(30) values and Acceptor Numbers are compared with each other and with corresponding literature values, determined in neat substituted phenols (Table 2). The influence of the phenolic substituents on both solvent parameters is discussed with respect to their electronic and steric effects as well as to the self‐association of phenols in solution. Polyhydroxybenzenes such as resorcinol and pyrogallol exhibit both high solvent polarity and acceptor properties, whereas substituents in positions 2 and 6 of phenols decrease their polarity and acceptor strength.
Biologically active glycosides from asteroidea, XXVI. Stereochemistry of the four diastereomers of ceramide and ceramide lactoside
Authors: Sugiyama Shigeo , Honda Masanori , Higuchi Ryuichi , Komori Tetsuya
Published: July 2007

The diastereomeric ceramides, (2S,3S,4R)‐, (2S,3S,4S)‐, (2S,3R,4S)‐, and (2S,3R,4R)‐2‐[(2R)‐2‐hydroxytetracosanoylamino]‐1,3,4‐hexadecanetriols 5–8 and the corresponding ceramide lactosides 1–4 have been synthesized. Compound 1 is almost identical with the natural specimen, acanthalactoside A. The physical data of these diastereomeric compounds are most useful to determine the stereochemistry of ceramides and ceramide lactosides, either isolated from natural sources or obtained by partial hydrolysis of gangliosides.
Reactions of 3‐vinylindole derivatives with dienophiles
Authors: Medio‐Simon Mercedes , Pindur Ulf
Published: July 2007

Reactions of 3‐(1‐cyclohexenyl)‐1,2‐dimethylindole (1a) and the 1,2‐dihydrocarbazole 1b with some carbo‐ and heterodienophiles are described. Thus, compound 1a reacts to give ene, Michael‐type, and Diels‐Alder adducts, depending on the dienophile and reaction conditions. The 3‐vinylindole 1b reacts with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione or N‐phenylmaleimide in a dehydrogenative reaction to yield the fully aromatized carbazole 8.
Sekundärstoffe aus dem chemischen Screening, 16. Inthomycine, neue Oxazol‐triene aus Streptomyces sp.
Authors: Henkel Thomas , Zeeck Axel
Published: July 2007

Secondary Metabolites by Chemical Screening, 161). – Inthomycins, New Oxazole‐Trienes from Streptomyces sp.

The oxazole‐triene metabolites inthomycin A to C (2, 4, 6) have been discovered by chemical screening in the culture broth of Streptomyces sp. (strain Gö 2). Its separation was successful only when the compounds had previously been transformed into the 3‐O‐(S)‐2‐phenylbutanoates 3, 5 and 7. The structures were deduced from their spectroscopic data, especially those taken from 2D‐NMR spectra. The natural products reveal differences in the (E/Z) configuration of its triene chains. By feeding [1‐13C]acetate to growing cultures of strain Gö 2, it was determined that C‐1 to C‐10 of the inthomycins biosynthetically originated via the polyketide pathway. Inthomycin A (2) has already been known as a substructure element of oxazolomycin (1) and probably is identical with the recently described phthoxazolin.
Preparation and use of chloromethyl (−)‐menthyl ether in the synthesis of optically pure α‐branched α‐amino nitriles
Authors: Shatzmiller Shimon , Dolithzky Ben‐Zion , Bahar Eliezer
Published: July 2007

The synthesis of optically pure chloromethyl (−)‐menthyl ether (2b) and its use in the synthesis of di‐(−)‐menthyl acetal (−)‐menthyl (+)‐menthyl acetals are described. The diastereomeric mixed acetals 7a, b and 8a, b are easily obtainable from the nitrones 5 and 6, KCN and 2b. The mixtures of diastereomers are separated into the pure components 7a, 7b and 8a, 8b by simple silica gel column chromatography. Hydrolysis of these products (H2O2/Na2CO3, ultrasound) followed by NO cleavage affords the heterocyclic α‐methyl‐α‐amino amides 11a, 11b and 12a, 12b. These are subsequently hydrolyzed to give the corresponding α‐methyl‐α‐amino acids with S and R configuration, respectively.
Synthesis of an enantiomerically pure sterol side‐chain precursor by enantioselective reduction of 1,3‐dihydroxy‐3‐methyl‐2‐butanone with baker's yeast
Authors: Schrötter Eberhard , Weidner Judith , Schick Hans
Published: July 2007

1,3‐Dihydroxy‐3‐methyl‐2‐butanone (1), accessible in 5 steps from 2‐methyl‐3‐butyn‐2‐ol, is reduced by baker's yeast to (R)‐(+)‐3‐methyl‐1,2,3‐butanetriol (2) with a high enantioselectivity. This chiral building block for the synthesis of various sterols with a modified side chain thus becomes available in 73% yield with an enantiomeric excess of 90%.
5‐Imino‐1,4,5,6‐tetrahydro‐1,2,3,4‐tetrazine aus 5‐Alkyliden‐4,5‐dihydro‐1H‐tetrazolen und elektrophilen Aziden
Authors: Quast Helmut , Regnat Dieter , Balthasar Jürgen , Banert Klaus , Peters Eva‐Maria , Peters Karl , Von Schnering Hans Georg
Published: July 2007

5‐Imino‐1,4,5,6‐tetrahydro‐1,2,3,4‐tetrazines Formed from 5‐Alkylidene‐4,5‐dihydro‐1H‐tetrazoles and Electrophilic Azides1)

The electrophilic azides 1 react with the 5‐alkylidenedihydrotetrazoles 8 already at low temperatures to produce high yields of the novel 5‐iminotetrahydro‐1,2,3,4‐tetrazines 10 besides molecular nitrogen. The configurations of (Z)‐10a, (E)‐10c, (Z)‐10d, and (E)‐10h are elucidated by means of X‐ray diffraction analyses. The formation of 10 is interpreted in terms of an initial [3 + 2] cycloaddition leading to the unstable spiro compounds 9. Ring opening of their dihydro‐1,2,3‐triazole ring generates the zwitterions 11 which lose molecular nitrogen with concomitant ring expansion of the dihydrotetrazole ring by a nitrogen 1,2‐shift. The tetrazines 10a–c and e are also obtained when 8a is generated from the tetrazolium salt 7a and trapped „in situ”︁ by the azides 1a–c and e.
Synthese von C‐Glycosiden der N‐Acetylneuraminsäure und weiteren Derivaten
Authors: Paulsen Hans , Matschulat Peter
Published: July 2007

Synthesis of C‐Glycosides of N‐Acetylneuraminic Acid and Other Derivatives

Reaction of the β‐pyranosyl chloride 1 of N‐acetylneuraminic acid with allyl(tributyl)stannane under radical‐induced conditions affords a mixture of the allyl C‐glycosides 2/3. After deprotection, the pure allyl α‐C‐glycoside 5 and the analogous β isomer 7 can be isolated. The allyl C‐glycosides 2 and 3 are converted into the corresponding epoxypropyl C‐glycosides 9 and 11 by epoxidation of the allylic group. Further modified allyl C‐glycosides are prepared from the C‐3‐hydroxylated N‐acetylneuraminic acid, which are available as pure α‐ and β‐C‐glycosides 19 and 21 after deprotection. At C‐3 modified compounds are also synthesized which have allyl and azido residues at C‐3. All compounds are interesting as potential inhibitors of sialidases, CMP sialate syntheses, and viral infection.
Preparation of nitrobenzaldehydes and nitrophenyl ketones by electrophilic amination of nitrobenzyl aryl sulfones
Authors: Wulf Jens‐Peter , Sienkiewicz Krzysztof , Mąkosza Mieczyslaw , Schmitz Ernst
Published: July 2007

Nitrobenzyl Aryl Sulfones 1a–g react with 3,3‐pentamethylene‐oxaziridine (2) with incorporation of an NH group into the benzylic position, followed by cleavage to nitrobenzaldehydes 4a–d and nitrophenyl ketones 4e–g, respectively.
Chiral anchor groups for oxoanions: Asymmetric synthesis of tetrasubstituted bicyclic guanidines
Authors: Schmidtchen Franz P. , Oswald Heike , Schummer Anita
Published: July 2007

The asymmetric synthesis of a tetrasubstituted bicyclic guanidine 1 is described. This salt may serve as an oxoanionbinding modul in open‐chain artificial receptors. The synthetic key step involves asymmetric alkylation of a Schöllkopf bislactim ether 8a/b to produce after protection/deprotection steps a chiral open‐chain triamine 13 which can be cyclized by thiophosgene as a C1‐building block to yield the target structure 1. The diastereoselectivity (%de) and enantioselectivity (%ee) of the synthetic pathway exceed 94%.
En Route to Thromboxane Compounds from Carbohydrates, II. Halolactonization of 4‐c‐Branched Alkyl Hex‐2‐enopyranosides
Authors: Pelyvás István F. , Lindhorst Thisbe K. , Batta Gyula , Thiem Joachim
Published: July 2007

Bromolactonization of alkyl 4‐C‐(aminocarbonylmethyl)hex‐2‐enopyranosides 1a and 4a in nonaqueous medium results in an unexpected α‐bromination in the C‐4 side chain.
Zur stereoselektiven Synthese von 2‐O‐Benzyl‐1‐O‐hexadecyl‐sn‐glycerol
Authors: Bauer Friederike , Rueß Klaus‐Peter , Liefländer Manfred
Published: July 2007

Stereoselective Synthesis of 2‐O‐Benzyl‐1‐O‐hexadecyl‐sn‐glycerol

Due to the versatility of 2‐O‐benzyl‐1‐O‐hexadecyl‐sn‐glycerol (7) as building block for various alkyl ether lipids and alkyl ether lyso‐lipids, 7 was prepared from D‐mannit following two different strategies. The final product 7 was obtained either via the intermediate 1,2‐O‐isopropylidene‐sn‐glycerol (1) or via 3,4‐O‐isopropylidene‐D‐mannit (8) in an overall yield of 6% or 11%, respectively.
5‐Alkyliden‐4,5‐dihydro‐1H‐tetrazole mit Vinyl‐ oder Phenyl‐Substituenten
Authors: Quast Helmut , Hergenröther Thomas
Published: July 2007

5‐Alkylidene‐4,5‐dihydro‐1H‐tetrazoles Substituted by Vinyl or Phenyl Groups.

The nitriles 7e–k and 10 are methylated by methyl triflate to afford the N‐methylnitrilium triflates 8e–k and 11 which are allowed to react with methyl azide to produce the tetrazolium triflates 9 · F3CSO3 and 12 · F3CSO3. The crystalline hexafluorophosphates 9 · PF6 and 12 · PF6 are obtained after anion exchange with ammonium hexafluorophosphate. Deprotonation of the tetrazolium cations 9c–g,j,k and 16 furnishes the corresponding alkylidenedihydrotetrazoles 3 and 17 as yellow, distillable oils or sublimable, low melting solids which are extremely sensitive towards moisture and oxygen. The parent compound 3c isomerizes readily to the amino‐1,2,3‐triazol 15. The rearrangement is initiated by traces of moisture inducing formation of methyl azide which acts as a catalyst. Similarily, 17 is cleaved into the amide 19 and phenyl azide which adds to unchanged 17 in a 1,3‐dipolar cycloaddition reaction yielding 18. Nuclear Overhauser experiments demonstrate that, of the two splittings 5J of 3d, the larger one stems from the long‐range coupling between the protons at the same side of the double bond, suggesting a contribution from a through‐space interaction to that coupling. The α‐carbon atoms of 3 and 17 resonate at higher field than those of 2‐alkylidenetetrahydroimidazoles 20 having the same substitution pattern, and even benzylpotassium (21). Furthermore, the down‐field shifts, caused by α‐deprotonation of the cations are smallest in the tetrazole series and hence indicative of extraordinary high electron densities at the α‐carbon atoms of 3 and 17 which may be interpreted in terms of contributions by dipolar resonance structures.
Reaktionen der Trialkylsilyl‐trifluormethansulfonate, XII. Aldol‐Additionsreaktionen mit 2,6‐Bis(trimethylsiloxy)thiophen‐Synthese bicyclischer γ‐Lactone
Authors: Rzehak Werner , Simchen Gerhard
Published: July 2007

Reactions of Trialkylsilyl Trifluoromethanesulfonates, XII. — Aldol‐Type Reactions with 2,6‐Bis(trimethylsiloxy)thiophene Synthesis of Bicyclic γ‐Lactones

In the presence of trimethylsilyl triflate (2) aromatic aldehydes 4 react with 2,6‐bis(trimethylsiloxy)thiophene (3) to yield the 3,4‐disubstituted thiosuccinic anhydrides 5. By hydrolysis of the products 5 in the presence of lead acetate the diaryl‐substituted cis‐bislactones 8 are obtained. Dialkyl‐substituted cis‐bislactones 10 are formed in a aldol addition of aliphatic aldehydes 9 to 3 catalysed by zinc chloride and subsequent hydrolysis of the intermediates. The synthesis of 3,4‐bis(dialkoxyalkyl)thiosuccinic anhydrides 7 is achieved by the reaction of 3 with carboxylic acid orthoesters 6 catalysed by 2.
Inhibitors of Phenylalanine Ammonia‐Lyase: 2‐Aminoindan‐2‐phosphonic Acid and Related Compounds
Authors: Zoń Jerzy , Amrhein Nikolaus
Published: July 2007

2‐Aminoindan‐2‐phosphonic acid (3) was synthesized for the first time both directly from 2‐indanone (7) as well as by alkylation of ethyl diethoxyphosphorylacetate with 1,2‐bis(bromomethyl)benzene (9) via 10–12, respectively. 2‐Hydroxyindan‐2‐phosphonic acid (5) was obtained also from 7 via its diisopropyl ester 8. Compound 3 was found to be a potent inhibitor of the plant enzyme phenylalanine ammonia‐lyase (EC 4.3.1.5) both in vitro and in vivo. Of the related 2‐aminoindan‐2‐carboxylic acid (4), compound 5, and 1‐aminocyclopentylphosphonic acid (6), only 4 inhibited the enzyme but was far less inhibitory than 3.
Enaminbildung aus 2‐Phenyl‐1,3‐indandionen und 1‐Phenylethylamin
Authors: Braun Manfred , Hanuschik Andreas , Steigel Alois , Nagy Edgar
Published: July 2007

Enamine Formation from 2‐Phenyl‐1,3‐indandiones and 1‐Phenylethylamine

The acid‐catalyzed condensation of 4‐methoxy‐2‐phenyl‐1,3‐indandione (3b) and (R)‐1‐phenylethylamine yields the regioisomeric enamines 4b and 5 in a ratio of 75:25. The structure 4b is assigned to the major isomer by 1H‐NMR spectroscopy and X‐ray structure analysis.
Imidazo[1,2‐a]pyrimidine 2′‐Deoxyribo‐ and 2′,3′‐Dideoxyribonucleosides: Glycosylation of the Nucleobase Anion
Authors: Seela Frank , Gumbiowski Rainer
Published: July 2007

The synthesis of the imidazo[1,2‐a]pyrimidine 2′‐deoxyribonucleosides 2a and 3a related to 2′‐deoxyguanosine or 2′‐deoxyinosine is described. Glycosylation of the nucleobase anion of 5 with 2′‐deoxy‐3,5‐bis‐O‐(4‐methylbenzoyl)‐α‐D‐erythro‐pentofuranosyl chloride (6) yielded stereoselectively the N‐1 β‐D‐deoxyribofuranoside 7. Under the same conditions the 2′,3′‐dideoxyrihalogenoses 11 and 14 were employed to afford anomeric mixtures of glycosylation products (12, 13 and 15, 16). The glycosylation products obtained from the 2′‐deoxyribo‐ and 2′,3′‐dideoxyribo halides were then converted into the final nucleosides (2a, b and 3a, b). The inhibitory activity of the imidazo[1,2‐a]pyrimidine 2′,3′‐dideoxynucleoside 5′‐triphosphates 28a and 28b against HIV reverse transcriptase was tested.
Synthesis of 4‐Epoxy‐4‐c‐methyleneglycosylceramides, Potential Glycosyltransferase Inhibitors
Authors: Plewe Michael , Sandhoff Konrad , Schmidt Richard R.
Published: July 2007

D‐Glucose was transformed into the 4‐deoxy‐4‐C‐methylene derivative 1. Dihydroxylation of 1 and then selective O‐tosylation afforded 4‐C‐(tosyloxymethyl)glucoside 3. Subsequent hydrogenolytic O‐debenzylation, selective O‐acetylation, treatment with a base, selective removal of the anomeric O‐acetyl group, and then treatment with trichloroacetonitrile in the presence of a base furnished 4‐epoxy‐4‐C‐methyleneglucosyl donor 7 (α,β mixture). Reaction of 7 with 3‐O‐acyl‐protected azidosphingosines 8a–c in the presence of Et2O.BF3 gave β‐glycosides 9a–c. Compounds 9a–c were transformed into the corresponding glucosylceramide derivatives 10a–c by treatment with triphenylphosphane/water and acyl anhydrides. Satisfactory removal of the O‐benzoyl protective group was difficult; however, O‐acetyl and O‐isobutyryl protective groups could be removed by methanolysis, thus affording from 10b, c the target molecules 11 and 12 with varying alkyl‐chain length. The epoxide 16 with galacto configuration, readily obtained from 1, on treatment with p‐toluenesulfonic acid furnished 4‐C‐(tosyloxymethyl)galactoside 18; this was transformed, as outlined for 3, into the target molecules 25b, c having galacto configuration in the sugar moiety.
6‐Siloxy‐Substituted 5,6‐Dihydro‐4H‐1,2‐oxazines as Key Building Blocks for Natural Products
Authors: Zimmer Reinhold , Collas Markus , Roth Michael , Reißig Hans‐Ulrich
Published: July 2007

Methyl (E)‐5‐bromo‐4‐oxo‐2‐pentenoate (6) and the corresponding oxime 5 were prepared in high yields by starting from methyl levulinate (3). The novel nitrosoalkene 8, generated in situ from oxime 5, smoothly added to silyl enol ether 7 to give 1,2‐oxazine 9 and nitrone 10 as byproduct. Methods are described transforming intermediate 9 into unsaturated diketo ester 11, or oximes 13, 15, and 18, which may serve as precursors of pyrenophorin. Reductive ring cleavage of 1,2‐oxazine 9 with Raney nickel efficiently afforded the saturated diketo ester 19. Its intramolecular aldol reaction gave cyclopentenone derivative 20, which is a known precursor of (Z)‐jasmone. Cycloaddition of methyl α‐nitrosoacrylate to silyl enol ether 22 provided 1,2‐oxazine 23. This compound was directly converted into the ant‐trail pheromone 24 by hexacarbonylmolybdenum‐promoted ring contraction.
Photochemische Studien, 62. Untersuchungen zur Photostabilität von Halometason und Prednicarbat in kristallinem Zustand sowie Kristallstruktur von Halometason
Authors: Reisch Johannes , Henkel Gerald , Ekiz‐Gücer Nurten , Nolte Gerald
Published: July 2007

Photochemical Studies, 62. — Investigation on the Photostability of Halometasone and Prednicarbate in the Crystal State and Crystal Structure of Halometasone

UV irradiation of halometasone (1) in the crystal state yields three photoproducts: 2‐chloro‐6α,‐9‐difluoro‐11β, 17α‐dihydroxy‐16α‐methyl‐3‐oxoandrosta‐1,4‐diene‐17β‐carbaldehyde (3), 2‐chloro‐6α,9‐difluoro‐11β‐hydroxy‐16α‐methylandrosta‐1,4‐diene‐3,17‐dione (4 and the dimerization product 2ξ‐chloro‐2ξ‐(2‐chloro‐6α,9‐difluoro‐11β,2→‐trihydroxy‐16α‐methyl‐3,20‐dioxopregna‐1,4‐dien‐21‐yl)‐6α,9‐difluoro‐11β,17, 21‐trihydroxy‐16α‐methylpregna‐4‐ene‐3,20‐dione (5). The structure of 5 is determined by the molecular packing of 1 in the crystal, as shown by an X‐ray analysis of 1. Two photo‐products are formed after irradiation of prednicarbate (2): 11β, 17‐dihydroxy‐21‐propionyloxypregna‐1,4‐diene‐3,20‐dione (6) and 17‐(ethoxycarbonyloxy)‐11β,21‐dihydroxypregna‐1,4‐diene‐3,20‐dione (7).
Synthesis of Furocoumarin‐Type Potential Intercalative Alkylating and Oxidizing Agents of DNA Through Dimethyldioxirane Epoxidation of Imperatorin and Its Derivatives
Authors: Abou‐Elzahab Mohamed M. , Adam Waldemar , Saha‐Möller Chantu R.
Published: July 2007

Epoxidation of imperatorin (1a) by dimethyldioxirane (DMD) affords the natural product prangenin (2a) in excellent yield. Similarly, alloimperatorin (1b) and its methyl and acetate derivatives 1b–d are epoxidized with DMD to give the corresponding epoxides 2b–d in quantitative yields. Furthermore, the reaction of the imperatorin allylic hydroperoxide 1e with DMD, and for comparison with m‐chloroperbenzoic acid (CPBA), yields the diastereomeric epoxy hydroperoxides (R*,S*)‐ and (R*,R*)‐2e in low but of opposite diastereoselectivity. Thus, for DMD the (R*,S*)/(R*,R*‐2e ratio is 56:44 and for CPBA 40:60.
Bausteine von Oligosacchariden, CII. Synthese von modifizierten Derivaten der 2‐Acetamido‐2‐desoxy‐D‐galactose zur Untersuchung der Substratspezifität der Core‐1‐β3‐Gal‐Transferase und der Core‐3‐β3‐GlcNAc‐Transferase der Biosynthese von O‐Glycoproteinen
Authors: Paulsen Hans , Rutz Volker , Brockhausen Inka
Published: July 2007

Building Units of Oligosaccharides, CII. – Synthesis of Modified Derivatives of 2‐Acetamido‐2‐deoxy‐D‐galactose for the Examination of Substrate Specificities of Core 1‐β3‐Gal‐Transferase and Core 3‐β3‐GlcNAc‐Transferase Involved in the Biosynthesis of O‐Glycoproteins

The 2‐, 3‐, 4‐, and 6‐deoxy derivatives of benzyl 2‐acetamido‐2‐deoxy‐α‐D‐galactopyranoside (7) have been synthesized to test substrate specificities of glycosyltransferases involved in the biosynthesis of O‐glycoproteins. The core 1‐β3‐Gal‐transferase dose not require the 6‐hydroxyl group for activity in contrast to the glycosylation reaction of the core 3‐β3‐GlcNAc‐transferase which requires the 6‐hydroxyl group. Compounds with reactive groups substituting the 6‐hydroxyl group such as the diazirine 45 could be suitable for photolabeling of the former enzyme. A column for affinity chromatography with the 6‐deoxy derivative as the ligand could be useful to separate the two enzymes during purification.
Neuartige Tricyclen aus Bis(arylthio)bicyclo[3.3.0]octadienen und Trimethylsilylcyanid in Gegenwart von Titan(IV)‐chlorid und Methanol
Authors: Quast Helmut , Carlsen Jürgen , Klaubert Christian Alexander , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg
Published: July 2007

Novel Tricyclic Products from Bis(arylthio)bicyclo[3.3.0]octadienes and Trimethylsilyl Cyanide in the Presence of Titanium Tetrachloride and Methanol.

A four‐step sequence converting ketones into α,β‐unsaturated nitriles is put to test with the ketones 7 and 13. The tetramethylcyclohexanone 7 reacts with thiophenol or 4‐chlorothiophenol in the presence of titanium tetrachloride and triethylamine to afford the phenyl vinyl sulphides 8. Treatment of 8 with a reagent, obtained from titanium tetrachloride and methanol, subsequent with trimethylsilyl cyanide produces the α‐phenylthionitriles 9 in moderate yields. Oxidation of 9a with 3‐chloroperbenzoic acid yields the α‐phenylsulphinylnitrile 12 which decomposes at temperatures as low as 100°C to furnish a quantitative yield of the unsaturated nitrile 11. — When the mixture of bifunctional vinyl sulphides C2‐, CS‐14a is allowed to react at −30°C with titanium tetrachloride/methanol and, subsequently, with trimethylsilyl cyanide, a mixture of the bicyclic α‐(phenylthio)nitriles exo‐15 and 16 and of the tricyclic products 17 and 18 is obtained. This mixture is separated by chromatography. At 20−25°C, the otherwise identical procedure furnishes an isomer of 17, viz. the tricyclic piperidine 21a which is derived from a novel heterocyclic system. The gross structures are based on spectroscopic evidence. The configurations of 16, 17, and 21b, and the structure of 18 as well, are established by X‐ray diffraction analyses. The mechanisms of the unexpected cyclization reactions leading to the tricyclic products 17, 18, and 21 are discussed.
Novel Concepts in Directed Biaryl Synthesis, XVI. Synthesis and Structure of Benzonaphthopyrans; Helically Distorted, Bridged Biaryls with Different Steric Hindrance at the Axis
Authors: Bringmann Gerhard , Hartung Thomas , Göbel Lothar , Schupp Olaf , Peters Karl , von Schnering Hans Georg
Published: July 2007

A simple two‐step synthesis of a series of ether‐type bridged biaryls 3, as favorable models for studies of helimerization processes, is described. Starting from the known corresponding lactones 1, a variety of differently substituted representatives 3 is prepared, greatly varying by the degree of steric hindrance and thus molecular distortion. NMR spectroscopy and especially X‐ray diffraction reveal the ethers 3 to be helically distorted, depending on the size of the ortho substituents R.
Wirkstoffe aus Pilzen, I. Isolierung, Synthese und biologische Wirkung von Coniothyriomycin sowie Synthese und Biotestung analoger offenkettiger Imide
Authors: Krohn Karsten , Franke Claudia , Jones Peter G. , Aust Hans‐Jürgen , Draeger Sigfried , Schulz Barbara
Published: July 2007

Biologically Active Metabolites of Fungi, I. — Isolation, Synthesis, and Biological Activity of Coniothyriomycin as well as Bioassay of Analoguos Open‐Chain Imides

The mixed open‐chain imide N‐(3‐chloro‐4‐hydroxyphenyl‐acetyl)fumarate (1), named coniothyriomycin, was isolated as metabolite of the fungus Coniothyrium. The natural product 1 and the analoguos imides 13–15 and 22–24 have been synthesized by base‐catalyzed condensation of the imidates 12a–f with acid chlorides 6a–c or the mixed anhydride 21. The compounds 1 and 13–15 were shown to posess remarkable fungicidal and herbicidal activities in short‐termed tests.
Enzymes in Organic Synthesis, 11. Enantioselective Lactonization of Methyl 3,5‐Dihydroxyalkanoates. — An Access to (3R,5S,6E)‐3‐Hydroxy‐7‐phenyl‐6‐hepten‐5‐olide by Enzyme‐Catalyzed Kinetic Resolution in Organic Solvents
Authors: Henkel Birgitta , Kunath Annamarie , Schick Hans
Published: July 2007

By enzyme‐catalyzed intramolecular transesterification methyl (±)‐(3R*,5S*,6E)‐3,5‐dihydroxy‐7‐phenyl‐6‐heptenoate (rac‐4) can be enantioselectively converted into the δ‐lactone 5. An enantiomeric excess of 80% was obtained by Pancreatin in diethyl ether at ambient temperature. Repetition of the enzyme‐catalyzed lactonization with enantiomerically enriched 3,5‐dihydroxy ester 4/ent‐4 enhanced the e.e. to >99%. Lipases of Pseudomonas and Candida sp. 382 tested in eight organic solvents were less efficient. The absolute configuration of 5, obtained as the major enantiomer in all experiments, has been determined by its conversion into the known (—)‐goniothalamin (6).
Glycosyl Imidates, 55. Synthesis of the Pentasaccharide Moiety of an Asterosaponin
Authors: Bing Han Xiao , Schmidt Richard R.
Published: July 2007

Reaction of 2‐O‐acetyl‐protected O‐galactosyl trichloroacetimidate 3 as glycosyl donor and 2,4‐di‐O‐unprotected xylopyranoside 2 as glycosyl acceptor furnished in the presence of Et2O · BF3 as catalyst regioselectively β‐(1→4)‐connected disaccharide 4 which gave upon subsequent reaction with O‐quinovosyl trichloroacetimidate 5 as donor β‐(1→2)‐connection, thus affording trisaccharide 6. Removal of the 2‐O‐acetyl group from the galactosyl moiety yielded acceptor 7; its glycosylation with donor 5 furnished β‐connected tetrasaccharide 8. This compound was transformed via 1‐O‐desilylation and then treatment with trichloroacetonitrile in the presence of a base into O‐tetraosyl trichloroacetimidate 10 as glycosyl donor. Reaction of 10 with 3‐O‐unprotected 2,4‐di‐O‐acetyl‐ and 2,4‐di‐O‐benzyl‐protected quinovosides 13 and 16 furnished the desired fully O‐protected pentasaccharides 17 and 18, respectively. Hydrogenolytic O‐debenzylation of 18 furnished the O‐unprotected target molecule 19 which was characterized as its O‐acetyl product 20.
Cycloaddition eines sehr reaktiven Cyanovinylcarbens mit Benzol und 3,4‐Dichlorcyclobuten Molekular‐ und Kristallstruktur von 2,3‐Dichlor‐5‐(1‐cyano‐2‐methyl‐1‐propenyl)‐5‐hausancarbonitril und 7‐(1‐Cyano‐2‐methyl‐1‐propenyl)‐7‐norcaradiencarbonitril
Authors: Franck‐Neumann Michel , Miesch Michel , Gries Stefan , Irngartinger Hermann
Published: July 2007

Cycloaddition of a Very Reactive Cyanovinylcarbene with Benzene and 3,4‐Dichlorocyclobutene. Molecular and Crystal Structure of 2,3‐Dichloro‐5‐(1‐cyano‐2‐methyl‐1‐propenyl)‐5‐housanecarbonitrile and 7‐(1‐Cyano‐2‐methyl‐1‐propenyl)‐7‐norcaradienecarbonitrile

The cyanovinylcarbene 2 has been generated by photolysis of 3,3‐dimethyl‐3H‐pyrazole‐4,5‐dicarbonitril (1) and the cycloaddition products with benzene and with 3,4‐dichlorocyclobutene have been isolated. The molecular structures of the cycloaddition products 7‐(1‐cyano‐2‐methyl‐1‐propenyl)‐7‐norcaradienecarbonitrile (3) and 2,3‐dichloro‐5‐(1‐cyano‐2‐methyl‐1‐propenyl)‐5‐housanecarbonitrile (4) were determined by X‐ray analyses. The bridging bond of the bicyclo[2.1.0]pentane group in 4 is shortened to 1.515 Å by the electronic interaction of this group with the cyano substituent. The vinyl substituent has no influence because of perpendicular orientation.
Absolute Configuration and Synthesis of 2‐Hydroxy‐2‐(1‐hydroxyethyl)‐3‐methyl‐γ‐butyrolactone, a Presumed Pheromone of Ithomiine Butterflies
Authors: Schulz Stefan
Published: July 2007

2‐Hydroxy‐2‐(1‐hydroxyethyl)‐3‐methyl‐γ‐butyrolactone (1) is a constituent of scent glands of male ithomiine butterflies. All diastereomers and the respective (3R)‐enantiomers were synthesized by starting from rac‐ or (3S)‐3‐methyl‐γ‐butyrolactone 3. Their relative configurations were determined by difference NOE‐NMR spectroscopy or by X‐ray diffraction analysis. The absolute configuration of the natural product was determined by gas chromatography on a chiral stationary phase of the respective dioxolane derivatives. The natural lactone could be shown to be the (1′S,2S,3R)‐enantiomer [(1′S,2S,3R)‐1a, ithomiolide A]. In addition, the corresponding ketone, (2S,3R)‐2‐acetyl‐2‐hydroxy‐3‐methyl‐γ‐butyrolactone [(2S,3R)‐5a, ithomiolide B], could be identified as a new natural product from Prittwitzia hymaenea.
Photochemical Reactions of 1‐Aryl‐2(1H)‐pyrimidinones in Alcohol
Authors: Nishio Takehiko
Published: July 2007

Irradiation of the 2(1H)‐pyrimidinones 1 in alcohols such as 2‐propanol and ethanol afforded the 1‐(alkoxycarbonylamino)‐3‐(arylimino)‐1‐propenes 4a–c, h and 2‐(alkoxycarbonylamino)‐4‐(arylimino)‐2‐pentenes 4d–g. These photoproducts are formed by trapping the isocyanate intermediates 2, generated initially by the Norrish‐type I cleavage of the ArN—CO bond of the 2(1H)‐pyrimidinones, with the alcohol.
α‐Amidoalkylation of Ambident Nucleophiles by Means of N‐Benzoylbenzaldimine
Authors: Dobrev Alexander , Benin Vladimir , Nechev Lubomir
Published: July 2007

tert‐Butyl esters 1a–c and N,N‐disubstituted amides 1d–h of carboxylic acids as well as N‐substituted pyrrolidinones 1i, j and 3‐morpholinone 1k are α‐amidoalkylated with N‐benzoylbenzylideneamine (2). The stereochemical course of the reaction is discussed.
A New Dinitroethylating Agent — N,N,N‐Trimethyl‐2,2‐bis‐(aci‐nitro)ethanaminium Hydroxide (Inner Salt)
Authors: Piotrowska Hanna , Wejroch Krystyna
Published: July 2007

2,2‐Dinitroethylation of some C‐H acidic compounds with N,N,N‐trimethyl‐2,2‐bis(aci‐nitro)ethanaminium hydroxide (inner salt) (1) is investigated and the products and byproducts are characterized.
Synthesis and Use of α‐Diazo Oxime Ethers in the Synthesis of Ethylene Diketone Bis(O‐methyloxime) Derivatives
Authors: Shatzmiller Shimon , Bercovici Sorin
Published: July 2007

Reaction of the lithium salts of oxime ethers 4a–c with methanesulfonyl azide gives the α‐diazo oxime ethers 5a–c. These novel compounds are stable up to 90°C, however, they decompose thermally in refluxing CCl4 and with PdCl2 catalysis to yield the ethylene diketone bis(O‐methoxyloxime) derivatives 6a–c in yields of 85–91%. The preparation and characteristic spectral features of 5a–c are described.
Reaktionen von 1,3‐Dipolen mit Heterocyclen, 8. Synthese von 1,8a‐Dihydro[1,2,4]triazolo[4,3‐a]pyridinen und Benzologen
Authors: Grubert Lutz , Jugelt Werner , Breß Hans Joachim , Köppel Hubert , Strietzel Ute , Dombrowski Anke
Published: July 2007

Reactions of 1,3‐Dipoles with Heterocycles, 8. — Synthesis of 1,8a‐Dihydro[1,2,4]triazolo[4,3‐a]pyridines and Benzologues

The C,N double bond of pyridine, quinoline and isoquinoline as heterodipolarophile react with diarylnitrilimines 2, generated in situ by dehydrohalogenation of N‐phenylbenzhydrazonoyl chlorides 1, in a cycloaddition with complete regioselectivity. A facile route to hitherto unreported 1,3‐diaryl‐1,8a‐dihydro[1,2,4]triazolo[4,3‐a]pyridines 3, 1,3‐diaryl‐3,3a‐dihydro[1,2,4]triazolo[4,3‐a]quinolines 4, and 1,3‐diaryl‐1,10b‐dihydro[1,2,4]triazolo[3,4‐a]isoquinolines 5 has been developed. In a similar way, cycloadditions are carried out with C‐ethoxy‐carbonyl‐ and C‐acetyl‐N‐phenylnitrilimines. The ring cleavage of 3 in acidic medium yields the corresponding [(arylhydrazono)methyl]pyridinium chlorides 7. The conversion of the open‐chain products back to 3 has been carried out in pyridine containing triethylamine. Anodic oxidation of 3–5 in aprotic medium affords the [1,2,4]triazolohetarenium perchlorates 9–11. The yields in such reactions are either similar or better than with chemical oxidants. The thermally initiated cycloreversion of 3 and 5 is discussed, judging from the facts that the thermolysis afford 2:1 cycloadducts.