bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of [13C]‐ and [2H]betulin for biological transformations
Authors: Tietze Lutz F. , Heinzen Horacio , Moyna Patrick , Rischer Matthias , Neunaber Horst
Published: July 2007

Selective acetylation of 1 at C‐28 afforded the monoacetate 2, which was oxidized to the 3‐oxo compound 8. H,D exchange at C‐2 in 8 followed by reduction with LiAlH4 led to [2‐2H]‐betulin (5). Reduction of 8 with NaBD4 or LiAlD4 yielded [3‐2H]betulin (6) besides different amounts of the respective 3α‐hydroxy compound 7. For the introduction of a CD2 or 13CH2 unit at C‐29 betulin diacetate 4 was ozonolyzed to give the known compound 10, which was treated either with CD2Br2, Zn, and TiCl4 in THF to yield the [29‐2H2] compound 11 or with [13C]methyltriphenylphosphonium iodide and potassium tert‐butoxide to afford the [29‐13C]‐labeled compound 11. Solvolysis of 11 and 13 with methanol and potassium carbonate afforded the desired compounds [29‐2H2]betulin (12) and [29‐13C]betulin (14).
Totalsynthese von Thymosin β4, 1. Klassische Synthese des Fragments [11–19] von Thymosin β4
Authors: Kapurniotu Afroditi , Voelter Wolfgang
Published: July 2007

Total Synthesis of Thymosin β4, 1. – Conventional Synthesis of the Fragment [11–19] of Thymosin β4

As part of the total synthesis of thymosin β4 two synthetic pathways for the synthesis of the thymosin β4 fragment [11–19] are described. The side‐chain functions are protected by tert‐butyl and the α‐amino residues by Z groups. As temporary protection of the carboxyl function the phenyl ester is successfully used.
Preparation of (R)‐ and (S)‐2‐alkyl‐2‐amino‐3‐(methylamino)propanoic and other 2,3‐diaminoalkanoic acid derivatives from a chiral imidazoline
Authors: Pfammatter Elmar , Seebach Dieter
Published: July 2007

t‐Butyl 2‐t‐butyl ‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate (Boc‐BMI, 1) is deoxygenated (→3), reductively carboxylated (→10, 11), converted to an imidazolinedicarboxylate 31 and subjected to a 1,2‐carbonyl‐group transposition (→34), The new chiral building blocks thus obtained are used to synthesize derivatives of (i) 1,2‐ethylenediamines (type4–11), of diaminopropanols (8, 16– 18) via the lithiated carbamate F, (ii) of 2‐alkyl‐2,3‐diaminopropanoic acid (20–26, 30) via the enolate H, (iii) of higher 2,3‐diaminoalkanoic acids (see 32, 33) via the Michael acceptor 31, and (iv) of simple α‐(methylamino) acids (type 35) via the enolate of 34. A number of free α,β‐diaminocarboxylic acids with a tertiary stereogenic center in the αposition is prepared (37–39). Some of these diamino acids are cyclized to β‐lactams (41–43) bearing an alkyl and a phenylsulfonylamido group in the 2‐position.
Enantioselektive Terpensynthesen durch Diels‐Alder‐Reaktion von 1‐(1‐Arylalkoxy)‐2‐methyl‐1,3‐butadien mit Isopren
Authors: Zadel Guido , Rieger Rainer , Breitmaier Eberhard
Published: July 2007

Enantioselective Terpene Syntheses by Diels‐Alder Reaction of 1‐(1‐Arylalkoxy)‐2‐methyl‐1,3‐butadiene with Isoprene

The (R)‐ and (S)‐1‐(1‐arylalkoxy)‐2‐methyl‐1,3‐butadienes 6 undergo [4 + 2] cycloadditions with excess isoprene (7) under pressure to yield not only the expected (4S,6R)‐ and (4R,6S)‐trans‐carveol (8) with up to 96% e.e. but also up to 40% of (R)‐ and (S)‐limonene (9) with up to 93% e.e. Asymmetric induction is proposed to arise from a transition state involving definite π stacking of one molecule of isoprenyl ether and two molecules of isoprene.
Ceramides from Urtica dioica roots
Authors: Kraus Rupert , Spiteller Gerhard
Published: July 2007

In methanolic extracts of stinging nettle roots (Urtica dioica) a special class of ceramides was detected. These ceramides contain a double bond in position 8 of the sphingoid base. With the typical amidic linkage the amino group of the sphingoid base (2‐amino‐1,3,4‐trihydroxy‐8‐octadecene) is either connected to an unbranched fatty acid with 20 – 25 carbon atoms or to a 2‐hydroxy fatty acid with the same chain length. Both classes of ceramides were separated from each other by thinlayer chromatoraphy. The members of each class were further separated as trimethylsilyl derivatives by gas chromatography. The structures of the ceramides were determined by mass, NMR and IR spectroscopy combined with hydrolysis experiments.
Tetra‐meso‐methylenporphyrinogene
Authors: Otto Christiane , Breitmaier Eberhard
Published: July 2007

Tetra‐meso‐methyleneporphyrinogens

While usual methods of carbonyl alkenylation such as the Wittig reaction fail when applied to xanthoporphyrinogens 1, methylenation of xanthoporphyrinogens 1 to tetra‐meso‐methyleneporphyrinogens 3 occurs with methyllithium in low to moderate yields.
Solanum alkaloids, 121. Partial Synthesis of the Steroid Alkaloids Teinemine, 22‐Isoteinemine, Etioline, and 25‐Isoetioline
Authors: Quyen Le Thi , Ripperger Helmut , Schreiber Klaus
Published: July 2007

The rare 16α‐hydroxylated steroid alkaloids teinemine [(22S,25S)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol, 8], 22‐isoteinemine [(22R,25S)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol, 10], etioline [(25S)‐22,26‐epiminocholesta‐5,22(N)‐diene‐3β,16α‐diol, 12], and 25‐isoetioline [(25R)‐22,26‐epiminocholesta‐5,22(N)‐diene‐3β,16α‐diol, 21] are synthesized from the abundant spirosolane alkaloids tomatid‐5‐en‐3β‐ol [(25S)‐22βN‐spirosol‐5‐en‐3β‐ol, 1] and solasodine [(25R)‐22αN‐spirosol‐5‐en‐3β‐ol, 15], respectively. The crucial stages of these syntheses are the conversions of 1 or 15 into the N‐protected (22S,25S)‐, (22R,25S)‐, and (22S,25R)‐22,26‐epimino‐3β‐hydroxycholest‐5‐en‐16‐ones 6, 7, and 18 as well as their reductions with sodium/ 2‐propanol to the 16α‐hydroxy compounds teinemine (8), 22‐isoteinemine (10), and (22S,25R)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol (19), respectively. By treatment with sodium methanolate the N‐chloro derivatives 9 and 11 of 8 and 10 afford etioline (12). In an analogous manner, the N‐chloro derivative 20 of 19 is converted into 25‐isoetioline (21).
Selektive enzymatische Schutzgruppenabspaltungen: Der n‐Heptylester als Carboxylschutzgruppe in der Peptidsynthese
Authors: Braun Peter , Waldmann Herbert , Vogt Walter , Kunz Horst
Published: July 2007

Selective Enzymatic Removal of Protecting Groups: n‐Heptyl Esters as Carboxy Protecting Functions in Peptide Synthesis

Amino acid heptyl (Hep) esters are accessible as generally crystalline hydro tosylates 3 from the amino acids by azeotropic esterification with 1‐heptanol in high yields. They can be condensed with Z‐, Boc‐, and Aloc‐protected amino acids to give the dipeptides 7–9 in the presence of 1‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline (EEDQ). From the fully protected dipeptides the N‐terminal protecting groups are cleaved by chemical methods without affecting the Hep esters. On the other hand, the heptyl esters can be hydrolyzed under mild conditions (pH = 7.0, 37°C) and with high yields by means of a lipase from Rhizopus niveus without attacking the N‐terminal urethane groups or the peptide bonds.
1H‐NMR spectra of all diastereomeric nitroalditols with a chain length up to C7, obtained from aldoses by the Fischer‐Sowden reaction
Authors: Köll Peter , Brandenburg Heinz , Seelhorst Willi , Stenns Claudia , Kogelberg Heide
Published: July 2007

The 1H‐NMR spectra of all diastereomeric alditols with a terminal nitro group up to a chain length of seven carbon atoms (31 compounds) have been recorded at 500 MHz in D2O. In most cases, a complete first‐order analysis has been performed. The spectra show systematic correlations with those of the parent alditols. Despite a special situation around the nitromethyl group no severe deviations of preferred conformations in solution from those of the parent alditols have been observed.
Pheromone synthesis, CXXV. Synthesis of the four possible stereoisomers of 3,7‐dimethylnonadecane, the female sex pheromone of Agromyza frontella Rondani
Authors: Mori Kenji , Wu Jiang
Published: July 2007

The synthesis of the four possible stereoisomers of 3,7‐dimethylnonadecane (1) has been achieved by starting from the enantiomers of methyl 3‐hydroxy‐2‐methylpropanoate (2) and (R)‐(+)‐citronellic acid (3).
Synthese langkettiger Benzo‐ und Naphthochinonaldehyde als Substrate für bakterielle Luciferasen
Authors: Jockers Half , Schmid Rolf D. , Rieger Hagen , Krohn Karsten
Published: July 2007

Synthesis of Long‐Chain Benzo‐ and Naphthoquinonealdehydes as Substrates of Bacterial Luciferases

The naphthoquinones 1 and 2 and the benzoquinones 28 and 29 have been alkylated with long‐chain‐functionalized aliphatic carboxylic acids 3–10 using the method of Torssell. The functional groups (COOH, OH, CHCH2) of the coupling products have been transformed into aldehyde groups affording quinoid aliphatic aldehydes with chain lengths ranging from C8 to C15. The quinoid aldehydes with an optimal chain length ranging from C9 to C11, especially the C9 aldehydes 27 and 31, were shown to be effective substrates of the bacterial luciferases from Vibrio harveyi and Photobacterium fischeri.
1,2,4‐Dithiazoliumsalze als Ausgangsstoffe für Pyrimidinderivate mit Oxo‐, Thioxo‐ oder Aminofunktion in 4‐Stellung
Authors: Briel Detlef
Published: July 2007

Synthesis of Pyrimidine Derivatives Having Oxo, Thioxo or Amino Functions at Position 4 from 1,2,4‐Dithiazolium Salts

The (thioaroylamido)acrylonitriles 2, obtained by reaction of 1,2,4‐dithiazolium salts 1 with ethyl cyanacetate, undergo ring transformation reactions by reaction with ammonium acetate, primary and secondary amines and form the pyrimidines 7–9. A possible mechanism for these reactions is discussed.
An unusual synthesis of tetrakis (trifluoromethyl)tetrathiafulvalene
Authors: Müller Harald , Lerf Anton , Fritz Heinz P.
Published: July 2007

Tetrakis(trifluoromethyl)tetrathiafulvalene (5) was formed in a phase‐transfer‐catalyzed unusual one‐step reaction by basic cleavage and subsequent alkylation of 1,3,4,6‐tetrathiapentalene‐2,5‐dione (thiapendione) (1) with 2,3‐dichlorohexafluoro‐2‐butene. As an example of the normal course of this reaction the synthesis of 4,5‐(ethylenedithio)‐1,3‐dithiol‐2‐one (3) is described.
Ein neues Butenolid aus Conyza bonariensis
Authors: Sanz Juan Francisco , Marco Juan Alberto
Published: July 2007

A New Butenolide from Conyza bonariensis

Extraction of aerial parts of Conyza bonariensis and chromatographic separation yielded the new butenolide 1, together with the acetylenic compounds trans‐lachnophyllum lactone (2) and cis‐lachnophyllum methyl ester (3), and the germacrane alcohol 4.
Chemie und Stereochemie der Iridoide, XV. Eine effiziente Synthese enantiomerenreiner (−)‐Specionin‐Analoga aus peracetylierten Iridoidglucosiden Kristall‐ und Molekülstruktur von (−)‐3′‐Methoxyspecionin
Authors: Weinges Klaus , Neuberger Karl , Schick Hartmut , Reifenstahl Uwe , Irngartinger Hermann
Published: July 2007

Chemistry and Stereochemistry of Iridoids XV. – An Efficient Synthesis of Enantiomerically Pure (−)‐Specionin Analogs from Peracetylated Iridoid Glucosides. – Crystal and Molecular Structure of (−)‐3′‐Methoxyspecionin

When peracetylated iridoid glucosides are submitted to hydroxymercuration and reduction with zinc the glucoside bond is cleaved exclusively. The aglycones can be regio‐ and stereoselectively transformed into specionin analogs. An example is the preparation of crystalline (−)‐3′‐methoxyspecionin (3b) from hexaacetyl‐6‐O‐vanilloylcatalpol (1d), which is readily available in larger quantities. The stereochemistry of 3b was determined by X‐ray crystallographic analysis.
Functionally substituted vinyl carbanions, 43. Convenient transformation of hexopyranosides into α‐methylene δ‐lactone derivatives
Authors: Kast Jürgen , Hoch Monika , Schmidt Richard R.
Published: July 2007

Treatment of glycopyranosyl phenyl sulfoxides 2ah, 1, 2bh, 1 with two equivalents of lithium diisopropylamide provides directly the C‐2‐lithiated glycal intermediates 3aAh, 1, 3bAh, 1 which, on reaction with formaldehyde as electrophile, furnish the 2‐hydroxymethyl derivatives 4ah, 1 and 4bh, 1, respectively. These compounds are transformed at elevated temperature and by acid catalysis directly into the α‐methylene‐δ‐lactones 5a, b. Correspondingly, from 2ah, 1 and methyl chloroformate as electrophile the 2‐methoxycarbonyl derivatives 6h and 61, respectively, are obtained. Treatment of 6h, 1 with Raney nickel leads to 2‐methoxycarbonyl‐substituted glycal 7 containing a β‐alkoxyacrylate moiety which again can be directly β‐C‐lithiated as demonstrated by the introduction of deuterium at C‐1.
Zur Darstellung der Anomeren des Hepta‐O‐acetylcellobiosyl‐, ‐lactosyl‐, ‐maltosyl‐ und ‐melibiosylazids
Authors: Pető Csaba , Batta Gyula , Györgydeák Zoltán , Sztaricskai Ferene
Published: July 2007

Synthesis of the Anomers of Hepta‐O‐acetylcellobiosyl, ‐lactosyl, ‐maltosyl, and ‐melibiosyl Azide

Synthesis and characterization by 13C‐NMR spectroscopy of the O‐acetylated 1,2‐cis and 1,2‐trans azides of cellobiose, lactose, maltose, and melibiose have been accomplished. 1,2‐trans Azides 1c, 2b–4b result from the stannic chloride catalyzed reaction of the β‐octa‐O‐acetates 1a–4a with trimethylsilyl azide, whereas the β‐chlorohepta‐O‐acetyldisaccharides 1d, 2c–4c afford, in an SN2 reaction in HMPT with lithium azide, the hitherto inaccessible 1,2‐cis azides 1e, 2d–4d.
Artificial deoxy glycosides of anthracyclines
Authors: Klaffke Werner , Pudlo Peter , Springer Dirk , Thiem Joachim
Published: July 2007

In Lewis acid mediated allylic rearrangement reactions of L‐rhamnal (1) and L‐fucal (2) with daunomycinon (6) 2′‐deoxyhex‐2′‐enopyranosides have been obtained exclusively. Furthermore, glycals 1 and 4 have been treated with the glycosyl acceptors 6, 7, and 9 and N‐iodosuccinimide (NIS) to produce the corresponding α‐configurated 2′‐deoxy‐2′‐iodo glycosides. Among these, 16 represents a bis (glycoside) with both benzylic aglycon positions substituted. In none of the above cases has a substantial amount of β‐glycoside been detected. Attempts to convert ε‐isorhodomycinon (8) into a glycoside on a preparative scale, under Lewis acid conditions have been unsuccessful. However, the α‐glycoside 13 has been obtained by the Helferich method.
Novel photocycloadditions of electron‐deficient nitrones to 2‐methyl‐2‐butene
Authors: Sehgal R. K. , Griffin G. W.
Published: July 2007

In Order to decrease the ground state reactivity and increase their potential for [3+2] cycloadditions, cyano‐ and methoxy‐carbonyl‐substituted nitrones 1a and 1b, respectively, were prepared and irradiated in the presence of electron‐rich alkenes such as 2 to afford the corresponding oxazolidines in which th oxygen atom becomes attached to the least substituted terminus of the olefin and nitrogen attaches to the more highly substituted counterpart. While the oxazolidines 12a and 12b obtained from 1b, via the intermediacy of oxaziridine(s) 15 and subsequent NO bond scission, are isolated and characterized, the oxazolidin(s) 18 formed bny cyclization of 1a are more labile and may undergo ionization to the stabilized oxazolinium ion 19 followed by nucleophilic attack by cyanide ion with accompanying ring opening to afford 6. A sequential diradical mechanism is proposed to rationalize the formation of the observed photoproducts 5 and 6.
Enantiomers of the muscarinic antagonist 1‐cyclohexyl‐1‐(4‐fluorophenyl)‐4‐piperidino‐1‐butanol (p‐fluoro‐hexahydro‐difenidol): Synthesis, absolute configuration, and enantiomeric purity
Authors: Strohmann Carsten , Bauerecker Sigurd , Cammenga Heiko K. , Jones Peter G. , Mutschler Ernst , Lambrecht Günter , Tacke Reinhold
Published: July 2007

The enantiomers of the antimuscarinic agent 1‐cyclohexyl‐1‐(4‐fluorophenyl)‐4‐piperidino‐1‐butanol [(R)‐ and (S)‐p‐fluorohexahydro‐difenidol] [(R)‐ and (S)‐2a] and their methiodides (R)‐3 and (S)‐3 were prepared with high enantiomeric purity. (R)‐2a and (S)‐2a (isolated as hydrochlorides) were obtained by catalytic hydrogenation (Pd/C contact) of the corresponding enantiomers of 1‐cyclohexyl‐1‐(4‐fluorophenyl)‐4‐piperidino‐2‐butyn‐1‐ol [(R)‐ and (S)‐4]. Reaction of (R)‐2a and (S)‐2a with methyl iodide led to (R)‐3 and (S)‐3, respectively. The unsaturated precursors (R)‐ and (S)‐4 (enantiomeric purity ⩾99.80 and ⩾99.94% e.e.; calorimetric analysis) were prepared by resolution of rac‐4 [available from 4‐FC6H4C(O)C6H11 by reaction with LiCCCH2NC5H10] using (R)‐ and (S)‐mandelic acid as resolving agents. The absolute configurations of the (R) and (S) enantiomers of 2a, 3, and 4 were determined by an X‐ray crystal‐structure analysis of (S)‐5, the methiodide of (S)‐4. (R)‐2a and (R)‐3 exhibit a higher affinity for muscarinic M1, M2, M3, and M4 receptors (by up to two orders of magnitude) than their corresponding antipodes (S)‐2a and (S)‐3, the degree of stereoselectivity depending on the receptor subtype involved. (R)‐2a represents a useful tool for muscarinic receptor research (affinity profile: M1 ≈ M3 ≈ M4 > M2).
Synthesis of sphingosine relatives, X. Synthesis of (2S,3R4E)‐1‐O‐(β‐D‐glucopyranosyl)‐N‐[30′‐(linoleoyloxy)triacontanoyl]‐4‐icosasphingenine, a new esterified cerebroside isolated from human and pig epidermis
Authors: Mori Kenji , Matsuda Hiroyuki
Published: July 2007

(2S,3R,4E)‐1‐O‐(β‐D‐Glucopyranosyl)‐N‐[30′‐(linoleoyloxy)triacontanoyl]‐4‐icosasphingenine (1) was synthesized from D‐glucose, L‐serine, 15‐pentadecanolide, and linoleic acid. The high‐field 1H‐NMR spectrum of 1 was identical with that of the esterified cerebroside isolated from human and pig epidermis.
N‐Vinylketenimine
Authors: Capuano Lilly , Braun Claudia , Kühn Frank
Published: July 2007

N‐Vinylketenimines.

The title compounds 5 are generated in situ from N‐vinyl‐iminotriphenylphosphoranes 1 and ketenes 2 in a Wittig‐type reaction. The phosphoranes are useful intermediates for the preparation of numerous heterocycles as illustrated by the formation of 1,3‐oxazines 8, pyridinones 9, pyrimidinones 10 and 1,3‐thiazines 11. Water adds readily to 5 to yield vinylacetamides 7, whereas thermal rearrangement gives rise to the isoquinoline 4 or the spiro system 6, respectively. Under very mild conditions, crystalline precursors (type 3) of the N‐vinylketenimines, which still contain the triphenylphosphonio group, have been isolated. These react like the N‐vinylketenimines generated in situ, giving however less byproducts.
Heterocyclisch [c]‐anellierte Cumarine aus 4‐Azido‐3‐cumarincarbaldehyden
Authors: Steinführer Thorsten , Hantschmann Achim , Pietsch Michael , Weißenfels Manfred
Published: July 2007

Heterocyclic [c]‐Condensed Coumarins from 4‐Azido‐3‐coumarincarbaldehydes

4‐Azido‐3‐coumarincarbaldehydes 2a–d are useful starting materials for syntheses of a variety of 3,4‐disubstituted coumarins as well as heterocyclic [c]‐fused coumarins, e. g. isoxazoles, pyrazoles and 1,5‐diazepines, under mild conditions. In these reactions, 2a–d are – despite of their thermolability — superior to the corresponding 4‐chloro‐3‐coumarincarbaldehydes 1a–d, from which they were prepared. An improved method for the preparation of 1a–d from 4‐hydroxy‐coumarins is described.
Reactions of 4‐Oxoalkanoic Acids, 4. Synthesis of (±)‐6‐Alkyl‐5‐oxa‐1‐azabicyclo[4.3.0]nonan‐9‐ones, (±)‐5‐Alkyl‐4‐oxa‐1‐azabicyclo[3.3.0]octan‐8‐ones, and Substituted 1,6‐Dioxa‐3,8‐diazacyclodecanes by Reaction of Ethyl 4‐Oxoalkanoates with 3‐Aminopropanol and 2‐Aminoethanol
Authors: Wedler Christine , Schick Hans , Scharfenberg‐Pfeiffer Doris , Reck Günter
Published: July 2007

Ethyl 4‐oxoalkanoates 1 react at ambient temperature in dry methanol in the presence of molecular sieve 3 Å in almost quantitative yield with 3‐aminopropanol and 2‐aminoethanol to form the bicyclic lactams rac‐2 and rac‐3, respectively. Surprisingly, the (±)‐5‐alkyl‐4‐oxa‐1‐azabicyclo[3.3.0]octan‐8‐ones rac‐3a–d dimerize in trichloromethane saturated with 2 N HCl to the ten‐membered heterocycles 4a–d. The structures of the substituted 1,6‐dioxa‐3,8‐diazacyclodecanes 4a and 4c have been determined by an X‐ray crystal analysis.
Cycloadditions of Nitrile Oxides to Itaconimides
Authors: Svêtlík Jan , Liptaj Tibor , Hanuš Vladimír
Published: July 2007

New spiro heterocycles, 1‐oxa‐2,7‐diazaspiro[4.4]non‐2‐ene‐6,8‐diones 3a–c and 8a, c were obtained in the reaction of itaconimides 1a–c with nitrile oxides 2 and 7.
Dithio‐ und Thionester, 53. Darstellung N‐geschützter α‐Aminodithiosäureester aus α‐Aminonitrilen und α‐Aminocarbonsäuren
Authors: Kohrt Arne , Hartke Klaus
Published: July 2007

Dithio and Thiono Esters, 53. — Synthesis of N‐Protected α‐Amino Dithioesters from α‐Amino Nitriles and α‐Amino Acids

The α‐amino nitriles 1 and 5 have been transformed into the thiolimido ester hydrochlorides 2 and 6 and sulfhydrolyzed to give the N‐protected α‐amino dithioesters 3 and 7. The α‐amino dithioesters 10 were obtained from 1 via the thioamides 8 and their S‐alkylation products 9. The optically active thioamides 12, prepared from naturally occurring L‐α‐amino acids, were converted into the optically active α‐amino dithioesters 7. The optical purity of the N‐protected dithioalanine esters 14 was determined by an HPLC analysis of the diastereomeric menthyloxycarbonyl derivatives 17.
Reaktionen der Trialkylsilyl‐trifluormethansulfonate, XI. Synthese von Derivaten der α‐Ketocarbonsäuren aus 2‐O‐funktionell substituierten Trimethylsilylketenacetalen
Authors: Simchen Gerhard , Siegl Gerald
Published: July 2007

Reactions of Trialkylsilyl Trifluoromethanesulfonates XI. — Synthesis of α‐Oxocarboxylic Acid Derivatives from 2‐O‐Functionalized Trimethylsilyl Ketene Acetals

The cyclic ketene acetals 3, 5 are prepared from the dioxolanone 2 resp. the oxazolidinediones 4 by silylation with trimethylsilyl triflate (1)/triethylamine. In an aldol addition/Peterson olefination reaction catalysed by 1 the ketene acetals 3, 5 yield the (E/Z)‐benzylidene derivatives 7, 12, 13 in reaction with aromatic aldehydes 6. In a side reaction the α‐(trimethylsilyl)benzylidene derivatives 8 are formed from 3 and 6. Compounds 7 can be hydrolysed to yield α‐ketocarboxylic acids 14. The latter are also obtained via β‐elimination of trimethylsilanol from 2,3‐bis(trimethylsiloxy)carboxylic acid esters 15 with trifluoroacetic acid anhydride/DMAP/pyridine.
Unerwartete Bildung von γ‐Lactamen aus 6H‐1,2,‐Oxazinen unter Lewis‐Säure‐Einwirkung
Authors: Zimmer Reinhold , Reißig Hans‐Ulrich , Lindner Hans Jörg
Published: July 2007

Unexpected Formation of γ‐Lactams from 6H‐1,2‐Oxazines Promoted by Lewis Acids

The reaction of 6H‐1,2‐oxazine 1 with trimethylsilyl cyanide in the presence of titanium tetrachloride provides α,β‐unsaturated γ‐lactam 3. Similarly, Lewis acid‐promoted addition of trimethyl phosphite towards 1 affords a mixture of γ‐lactams 8 and 9. The structure of 9 was established by X‐ray analysis. A plausible mechanism for the formation of these γ‐lactams by Lewis acid‐induced ring contraction is proposed.
threo‐3‐Alkyl‐ and ‐Arylglutamic Acid Derivatives by Michael Additions of Boc‐BMI Li‐Enolates to 2,6‐Di‐t‐butyl‐4‐methoxyphenyl Alkenoates on the Diastereoselectivity of the Coupling of Trigonal Centers Involving Heterocyclic Li‐Enolates
Authors: Suzuki Keisuke , Seebach Dieter
Published: July 2007

The conjugated esters5,6,8,9mentioned in the title are prepared from the corresponding aryl acetate4and aldehydes by aldol condensation (direct enoylation of the hindered phenol with the corresponding unsaturated acid chlorides gave only poor yields). To avoid double‐bond shifts, the 4‐phenyl 2‐butenoate7awas prepared from the saturated one by selenation/elimination (see7b,cin Scheme 1). In contrast to methyl and ethyl crotonates, reacting in poor yields and with low selectivities (→11,12), the hindered aryl enoates combine with the Li‐enolate of1[(S)‐Boc‐BMI, a chiral glycine derivative] to give single products13a–17a(⩾95% ds) in high yields (78–96% of purified samples, Scheme 2). The configuration of the two newly formed stereogenic centers and thus the mode of coupling of the trigonal centers in the Michael addition (DandEin Scheme 4) is derived for the methyl (13a) and benzyl substituted (15a) derivatives by multiple chemical correlation (see19–24in Scheme 3). It is shown that pure (2S,3R)‐glutamic acids22,23can be isolated by hydrolysis of the adducts13a, 15aof conjugate addition. — The results of the aldol, Michael and nitro olefin additions of heterocyclic Li‐enolates are collected and compared (Scheme 5, Table 1). Possible reasons for the high diastereoselectivity and a typical coupling mode of most reactions involvingN‐acylimidazolidinone andN‐acyloxazolidinone Li‐enolatesM,Oare discussed (seeWin Scheme 6).
Antibiotika aus Gleitenden Bakterien, 45. Phenalamide, neue HIV‐1‐Inhibitoren aus Myxococcus stipitatus Mx s40
Authors: Trowitzsch‐Kienast Wolfram , Forche Edgar , Wray Victor , Reichenbach Hans , Jurkiewicz Elke , Hunsmann Gerhard , Höfle Gerhard
Published: July 2007

Antibiotics from Gliding Bacteria, 45. — Phenalamides, New HIV‐1 Inhibitors from Myxococcus stipitatus Mx s40

We report on the isolation and structure elucidation of the phenalamides A1 (1), A2 (2), A3 (3), B (4), and C (5), amides from alaninol and ω‐phenyl‐substituted unsaturated carboxylic acids (a pentaene carboxylic acid in 1 — 4, and a tetraene carboxylic acid chromophore in 5). Compounds 1 — 3 are E/Z isomers with the configuration: 6Z for 1, 4 represents 8‐methyl‐1, and for 5 we determined the 10,11‐double bond in 2 to be epoxidated. C‐16 in 1 has the S configuration, as revealed by ozonisation and isolation of the (2S)‐(+)‐2‐methyl‐4‐phenylbutyric acid. By comparison of their respective CD spectra all the other centers of chirality in 1 should have the same stereochemistry as in the related compound myxalamid B. 1 seems to be identical to stipiamide. First results of enrichment experiments show that the biogenesis of 1 starts with phenylalanine, which after transamination and decarboxylation is connected with propionate and acetate units to generate the highly unsaturated fatty acid. The second amino acid unit alanine terminates the biosynthesis.
Terpenes and Terpene Derivatives, XXIX. Synthesis and Olfactive Properties of (—)‐ and rac‐Silphiperfol‐5‐en‐3‐ol and of Some Tris‐nor Derivatives
Authors: Weyerstahl Peter , Brendel Joachim
Published: July 2007

The new sesquiterpene alcohols silphiperfol‐5‐en‐3‐ol [(—)‐1a] and the corresponding 7‐epi compound (+)‐1b, important constituents of the essential oil of Artemisia laciniata have been synthesized in 13 steps by starting from (R)‐(+)‐pulegone (6) in an overall yield of 8%. The key reaction is the coppercatalyzed 1,4‐Grignard addition of the iodo acetal 34 to the enone (+)‐4 in the presence of TMSCI and TMEDA to give the silyl ether 38. Hydrolysis with spontaneous aldol cyclization and dehydration leads to the silphiperfolenones (+)‐2a, b which are separable by flash chromatography. The reduction with L‐selectride® gives the alcohols (—)‐1a and (+)‐1b which are identical in all physical properties with the isolated natural compound. With LiAlH4 the diastereoisomers 42a, b are formed. Olfactive evaluation of the isomers (—)‐1a and (+)‐1b has shown that the odor of the naturally occurring mixture of 1a, b with the descriptors woody, ambergris, slightly camphoraceous is correctly assigned. (—)‐1a represents the more woody and camphoraceous, (+)‐1b the more animal facette of ambergris. The odor of rac‐1a, b of the diastereoisomers 42a, b and of the ketones (+)‐2a, b is also described as well as that of the tris‐nor‐silphiperfolene derivatives 29–31.
Synthesis of Methyl 2‐O‐Benzyl‐6‐deoxy‐3‐c‐methyl‐α‐D‐mannopyranoside and Methyl α‐D‐Evalopyranoside
Authors: Žagar Cyrill , Scharf Hans‐Dieter
Published: July 2007

Methyl 2‐O‐benzyl‐6‐deoxy‐3‐C‐methyl‐α‐D‐mannopyranoside (2) was synthesized in ten steps by starting from the readily available methyl 2,3‐anhydro‐4,6‐O‐benzylidene‐α‐D‐allo‐pyranoside (3). The key step was the stereoselective cis‐hydroxylation (cat. osmium(VIII) oxide) of methyl 2‐O‐benzyl‐4,6‐O‐benzylidene‐3‐deoxy‐3‐C‐methylene‐α‐D‐arabino‐hexo‐pyranoside (9), producing methyl 2‐O‐benzyl‐4,6‐O‐benzylidene‐3‐C‐hydroxymethyl‐α‐D‐mannopyranoside (11) and its C‐3 epimer in a ratio of 20: 1. Catalytic hydrogenation of 2 gave methyl 6‐deoxy‐3‐C‐methyl‐α‐D‐mannopyranoside (methyl‐α‐D‐evalopyranoside, 1).
Chiral Organometallic Reagents, VII. On the Configurational Stability of α‐Methylbenzyllithium
Authors: Hoffmann Reinhard W. , Rühl Thomas , Chemla Fabrice , Zahneisen Thomas
Published: July 2007

α‐Methylbenzyllithium (6) should possess either central or planar chirality. The rate of enantiomerization of 6 at — 78°C was found to be faster than its addition to the amide 7, the ketone 8, or to the aldehyde 10, according to a test based on kinetic resolution. The benzyllithium compound 6 thus behaves in THF essentially as a prochiral entity.
Bausteine von Oligosacchariden, CIII. Synthese von modifizierten Derivaten des Disaccharides β‐D‐Gal‐(1 → 3)‐α‐D‐GalNAc zur Untersuchung der Substratspezifität der Core‐2‐β6‐GlcNAc‐Transferase und α‐3‐Sialyltransferase der Biosynthese von O‐Glycoproteinen
Authors: Paulsen Hans , Rutz Volker , Brockhausen Inka
Published: July 2007

Building Units of Oligosaccharides, CIII. — Synthesis of Modified Derivatives of the Disaccharide β‐D‐Gal‐(→3)‐α‐D‐GalNAc for the Examination of Substrate Specificities of Core 2‐β6‐GlcNAc‐Transferase and α‐3‐Sialyltransferase Involved in the Biosynthesis of O‐Glycoproteins

Derivatives of benzyl β‐D‐galactopyranosyl‐(1→3)‐2‐acet‐amido‐2‐deoxy‐α‐D‐galactopyranoside have been synthesized. The 6′‐, 4′‐ and 3′‐OH group of the galactose moiety as well as the 6‐ and 4‐OH and the 2‐acetamido group of the 2‐acet‐amido‐2‐deoxy‐D‐galactose moiety have been selectively substituted by the corresponding deoxy function. The compounds are useful in studies of the substrate specificities of the core 2‐β6‐GlcNAc‐transferase and the α3‐sialyltransferase involved in the biosynthesis of O‐glycoproteins.
Westphal Condensation of N‐Aminocycloiminium Salts Synthesis of Fused Pyridazinium Derivatives
Authors: Matia María P. , García‐Navío José L. , Vaquero Juan J. , Alvarez‐Builla Julio
Published: July 2007

A series of α‐alkyl‐N‐aminoazinium and ‐azolium salts 1–15 have been condensed with 1,2‐dicarbonyl compounds to produce new heterocyclic cationic species 17–25 with a quaternary nitrogen atom in the bridgehead position.
Zur Chemie der Mucohalogensäuren, VII. Asymmetrische Synthese von β‐Lactam‐Derivaten durch Keten — Imin‐Cycloaddition unter Verwendung chiraler Mucochlorsäure‐Derivate
Authors: Duczek Wolfram , Jähnisch Klaus , Kunath Annamarie , Reck Günter , Winter Gabriele , Schulz Burkhard
Published: July 2007

Chemistry of Mucohalic Acids, VII. — Asymmetric Synthesis of β‐Lactam Derivatives by the Ketene—Imine Cycloaddition Utilizing Chiral Mucochloric Acid Derivatives

The ketene derivative 5 of the chiral pyrrolinon 4 underwent nonconcerted [2 + 2] cycloadditions with imines leading to cis‐β‐lactams 6a–d with ≫99% diastereomeric excess. rac‐4 was resolved efficiently by crystallisation of diastereoisomeric ammonium salts with brucine. (5S)‐4 provided the β‐lactam (3′S,4′R,5S)‐6a. The absolute configuration of 6a was determined by X‐ray analysis. The synthesis of the minor β‐lactam 7 was achieved independently.
Synthesis of α‐N‐Ketosides of N‐Acetylneuraminic Acid by Using Phase‐Transfer Catalysis
Authors: Rothermel Jörg , Weber Bernd , Faillard Hans
Published: July 2007

α‐N‐Ketosides of N‐acetylneuraminic acid (Neu5Ac) can be synthesized by using azide and thiocyanate salt as aglycone under conditions of phase‐transfer catalysis (PTC). The catalytic hydrogenation of the 2‐α‐azido ketoside 3 leads to the 2‐α‐amino ketoside 4 in good yield. This 2‐α‐amino ketoside 4 can be transformed into the 2‐α‐acetamido ketoside 5 and the 2‐α‐benzoylamido ketoside 6. Zemplén deacetylation and saponification give the corresponding 2‐N‐acyl ketosides 7 and 8, which cannot be hydrolyzed by neuraminidase (Clostridium perfringens). Treatment of the 2‐α‐amino ketoside 4 with p‐nitrobenzaldehyde results in the formation of p‐nitrobenzylideneamine 9. Based on the strict stereoselectivity of the PTC glycosidation reaction with sialic acid derivatives and the exclusive formation of the N‐ketoside 10 in the reaction with potassium thiocyanate, a model of the mechanism of the PTC glycosidation procedure with sialic acid derivatives has been evaluated.
Fused Heterocycles, VII. Synthesis and Stereochemistry of Tetracyclic Benzodiazepines
Authors: Tóth Gábor , Lévai Albert , Szőllősy ÁRon
Published: July 2007

Benzodiazepines 3a–d have been synthesized by the reaction of exocyclic α,β‐unsaturated ketones 1a–d with 1,2‐phenylenediamine in hot ethanol. Acetylation of compounds 3a–d with a mixture of acetic anhydride and anhydrous pyridine affords the N‐acetyl derivatives 4a–d. Structure and stereochemistry of the synthesized compounds have been elucidated by various NMR techniques.
Synthesis of Heterocyclic Propellanes by 1,3‐Dipolar Cycloaddition of 2,6‐Dichlorobenzonitrile Oxide to 2,3‐Fused Indoles. Catalytic Hydrogenation of the Cycloadducts
Authors: Malamidou‐Xenikaki Elizabeth , Coutouli‐Argyropoulou Evdoxia
Published: July 2007

N‐Methylcycloalkano[b]indoles 1a, 1c–d and N‐methylindeno[1,2‐b]indole (1e) react with 2,6‐dichlorobenzonitrile oxide (2) to afford regioselectively propellanes 3. Catalytic hydrogenation of compounds 3 proceeds via the labile β‐hydroxyimines 4, which are further decomposed to the starting indole and 2,6‐dichlorobenzonitrile. In one case the intermediate imine 4e is stable and isolated in pure form.
Asymmetric Syntheses of α‐Aminophosphonic Acids, V. Synthesis of Enantiomerically Pure Diethyl 2‐Pyrrolidinyl‐ and 5‐Oxo‐2‐pyrrolidinylphosphonates
Authors: Groth Ulrich , Richter Lutz , Schöllkopf Ulrich
Published: July 2007

Enantiomerically pure 3‐ and 4‐substituted phosphonic acid derivatives 5 of pyroglutamic acid were prepared by a Michael addition of the lithiated (+)‐camphor derivative 2 to α,β‐unsaturated esters and subsequent hydrolysis. The reduction of the lactams 5 with LiBH4/BF3 · OEt2 afforded substituted phosphonic acid analogues 7 of proline.
Dithio‐ und Thionester, 55. Synthese von N‐geschützten, optisch aktiven α‐Aminothionsäureestern
Authors: Brutsche Andreas , Hartke Klaus
Published: July 2007

Dithio and Thiono Esters, 55. — Synthesis of N‐Protected, Optically Active α‐Amino Thiono Esters

The N‐protected α‐amino amides 1 are O‐alkylated with trialkyloxonium tetrafluoroborates to form the iminium salts 2. Sulfhydrolysis of 2 yields the α‐amino thiono esters 3. This reaction sequence allows the preparation of enantiomerically pure 3.
Pheromone Synthesis, CXLII. A New Synthesis of (3S,4R)‐8‐Nonene‐3,4‐diol, the Key Intermediate for the Synthesis of (+)‐endo‐Brevicomin
Authors: Mori Kenji , Kiyota Hiromasa
Published: July 2007

(3S,4R)‐8‐Nonene‐3,4‐diol (2), the key intermediate for the synthesis of the bark beetle pheromone (+)‐endo‐brevicomin (1), has been synthesized in 46% overall yield (10 steps) based on erythritol (6) by employing lipase‐mediated asymmetric acetylation as one of the steps.
Pheromone Synthesis, CXXXIV. Synthesis of the Four Possible Stereoisomers of 13,17‐Dimethylnonatriacontane, a Kairomone for the Wasp Trichogramma nubilale
Authors: Mori Kenji , Wu Jiang
Published: July 2007

The synthesis of the four possible stereoisomers of 13,17‐dimethylnonatriacontane (1) has been achieved by starting from (R)‐citronellol (4) and the enantiomers of methyl 3‐hydroxy‐2‐methylpropanoate (5).
Kondensierte 1,2‐Dithiole, II. Synthese von Thieno‐1,2‐dithiolen
Authors: Stachel Hans‐Dietrich , Schorp Matthias , Zoukas Thomas
Published: July 2007

Ring‐Fused 1,2‐Dithioles, II. — Synthesis of Thieno‐1,2‐dithioles

A series of thieno‐1,3‐dithiines 5 has been synthesized starting with the β‐thioxoester 4. The dithiines undergo oxidative ring contraction to the corresponding thieno‐1,2‐dithioles 6. Analogously, the dithiolo‐dithiines 8 form the 1,2‐dithiolo‐1,2‐dithioles (1,2,4,5‐tetrathiapentalenes) 14 by ring contraction. — The ester function of 6f is easily removed to give 2, the thioanalog of the antibiotic thiolutine.
Synthesis of Functionalized 1,2,3,4‐Tetrahydro‐β‐carbolines from Enamino Ketones
Authors: Tietze Lutz F. , Wichmann Jürgen
Published: July 2007

Reaction of tryptamine (1) with 2 and 3 gives the enamino ketones 4a and 5, resp., which on treatment with trifluoroacetic acid lead to the 2‐substituted indoles 8 and 9, respectively. Acylation of 4a followed by reaction with trifluoroacetic acid or a Lewis acid affords the 1,2,3,4‐tetrahydro‐β‐carbolines 7b–e in excellent yields. Treatment of 8 with anhydrides like (CF3CO)2O also yields the 1,2,3,4‐tetrahydro‐β‐carboline 7f. The trichloromethylcarbonyl group in 7 can easily be converted into an ester moiety by reaction with an alcohol in the presence of K2CO3.
Synthesis of Some Ribose‐Alkylated 5′‐UMP Derivatives
Authors: Khan Khurshid Alam , Qudrat‐e‐Khuda M. , Fizza Kaniz , Ahmad Viqar Uddin
Published: July 2007

The reaction of 5′‐UMP (1) with methyl, ethyl, n‐propyl, and isopropyl iodide under strongly alkaline conditions gave predominantly ribose‐alkylated derivatives 2–11. The structures of the products have been assigned by using UV spectroscopy, paper electrophoresis, 1H‐NMR spectroscopy and fast‐atom bombardment mass spectrometry in the negative ion mode.
Solanum Alkaloids, 124. Preparation of N‐Hydroxyspirosolane Alkaloids
Authors: Ripperger Helmut
Published: July 2007

The N‐Hydroxyspirosolane alkaloids N‐hydroxysolasodine (1) and N‐hydroxytomatidine (10) as well as the N‐hydroxy‐22,26‐epiminocholestene 7 have been prepared by oxidation of the respective amines 2, 11, and 5 with hydrogen peroxide in the presence of selenium dioxide.
Cytochrom‐P‐450‐Modellreaktionen, 2. Isolierung und Charakterisierung eines Mangan(IV)‐Pentafluoriodosylbenzol‐Porphinato‐Komplexes als Modell der aktiven Spezies im Katalysecyclus von Cytochrom‐P‐450
Authors: Volz Heinrich , Müller Wilhelm
Published: July 2007

Cytochrome P‐450 Model Reactions, 2. — Isolation and Characterization of a Manganese(IV)‐Pentafluoroiodosylbenzene‐Porphinato Complex as a Model of the Active Species of the Catalytic Cycle of Cytochrome P‐450

The isolation at −78°C and characterization of the crystalline reactive manganese(IV)‐porphinato complex Mn(TDCPP)‐(C6F5IOCl)Cl (4) is described. 4 is compared with the manganese(IV)‐porphinato complexes Mn(TDCPP)(C6H5IOCl)2 (2) and Mn(TDCPP)(OCH3)2 (3). The stoichiometric reaction of 4 with triphenylphosphane yields 1.5 equivalents of triphenylphosphane oxide, 1.0 equivalents of Mn(TDCPP)Cl (1), and 1.0 equivalents of pentafluoro‐iodobenzene. 4 epoxidizes stilbene, oxygenates cyclohexane, and oxidizes anthracene to anthraquinone.
Studies on Heterocyclic Enaminonitriles, XII. Reactions of 4,5‐Dihydro‐2‐morpholino‐ (and ‐2‐pyrrolidino)‐3‐furancarbonitriles with Dichlorocarbene
Authors: Yamagata Kenji , Takaki Mikiko , Yamazaki Motoyoshi
Published: July 2007

The reaction of 4,5‐dihydro‐2‐morpholino‐ (and ‐2‐pyrrolidino)‐3‐furancarbonitriles 1a, c, d and 2a, c, d with dichlorocarbene gave 4‐(2,4‐pentadienoyl)morpholines 3a, c, d and 1‐(2,4‐pentadienoyl)pyrrolidines 4a, c, d. Similarly, the reaction of 4,5‐dihydro‐5‐methyl‐2‐morpholino‐ (and ‐2‐pyrrolidino)‐3‐furancarbonitrile 1b and 2b afforded the corresponding 4‐(2‐chloro‐3‐cyano‐2,4‐hexadienoyl)morpholine (3b) and 1‐(2‐chloro‐3‐cyano‐2,4‐hexadienoyl)pyrrolidine (4b). The starting compounds 1a–d and 2a–d were synthesized by the reaction of 2‐amino‐4,5‐dihydro‐3‐furancarbonitriles with morpholine (and pyrrolidine) in the presence of trimethylamine hydrochloride in dioxane.
Chiral Organometallic Reagents, X. On the Kinetic Diastereoselectivity in the Bromine/lithium Exchange in 1,1‐Dibromo‐2‐methylalkane Derivatives
Authors: Hoffmann Reinhard W. , Mikolaiski Wolfgang , Brumm Karen , Brune Ulrike
Published: July 2007

The kinetically controlled diastereoselectivity in the bromine/lithium exchange reaction of the dibromoalkanes 6 and 7 has been found to be moderate (75:25) and (67:33). The thermodynamic ratio of the epimeric organolithium compounds 12a/b and 17a/b, respectively, has been determined to coincide with the kinetic ratios given above.
Synthesis and Properties of Methylthiopyrazolo[3,4‐d]pyrimidine 2′‐Deoxy‐β‐D‐ribonucleosides
Authors: Oertel Frank , Winter Holger , Kazimierczuk Zygmunt , Vilpo J. A. , Richter Peter , Seela Frank
Published: July 2007

The synthesis of the 3‐ and 4‐(methylthio)pyrazolo[3,4‐d]pyrimidine N1‐ and N2‐2′‐deoxy‐β‐D‐ribonucleosides 2b, 15 is described. Anionic glycosylation of 5‐amino‐3‐(methylthio)‐4‐pyrazolecarbonitrile (4) or 4‐(methylthio)pyrazolo[3,4‐d]pyrimidine (12) with 2‐deoxy‐3,5‐di‐O‐(4‐methylbenzoyl)‐α‐D‐erythro‐pentofuranosyl chloride (5) gave the regioisomeric N1‐and N2‐nucleosides 6, 7, 13, and 14. The N1 isomer was the main product in the reaction of 12, and the N2 compound was the preferred product in the glycosylation of 4. Glycosylation in suspension (12) yielded an appreciable amount of the N2 α‐D‐isomer 16. 4‐Aminopyrazolo[3,4‐d]pyrimidine 2′‐deoxyribonucleosides 3a, b with a methylthio group at C‐3 are resistant to deamination by adenosine deaminase and inhibit the proliferation of leukemia cell lines.
Pheromone Synthesis, CXLIII. Synthesis and Absolute Configuration of the Hemiacetal Pheromone of the Spined Citrus Bug Biprorulus bibax
Authors: Mori Kenji , Amaike Masayasu , Oliver James E.
Published: July 2007

(3S,4R,1′E)‐3,4‐Bis(1′‐butenyl) tetrahydro‐2‐furanol (1) was synthesized from 1,3‐butadiene and maleic anhydride by employing the HLADH‐catalyzed enzymatic oxidation of meso‐diol 2 as the key step, and shown to be identical with the pheromone produced by the dorsal abdominal glands of the male spined citrus bug (Biprorulus bibax).
Photochemische Studien, 64. Photostabilität von Glucocorticoiden in kristallinem Zustand
Authors: Reisch Johannes , Iranshahi Lotfollah , Ekiz‐Gücer Nurten
Published: July 2007

Photochemical Studies, 64. — Photostability of Glucocorticoids in the Solid State

Most of the pharmacopoeia require that the glucocorticoids hydrocortisone (1), cortisone (2), hydrocortisone 21‐acetate (3) and cortisone 21‐acetate (4) must be protected from light during storage. The present study shows that UV irradiation of these compounds in the solid state leads to the loss of the side chain at C‐17. Two 17‐ketosteroids, 11β‐hydroxy‐4‐androstene‐3,17‐dione (6) and 4‐androstene‐3,11,17‐trione (7), were obtained as photoproducts (yields 3% and 4%, respectively).
Arene Hydrides, 10 Michael Additions of Anthracene Hydride. Selective Reduction of the ArCC Moiety by Fragmentation of the Michael Adduct
Authors: Sommer Andreas , Stamm Helmut
Published: July 2007

Anthracene hydride (AH−) in THF undergoes Michael addition onto the acrylic acid derivatives 1 and 2. Secondary reactions of the first formed anions 3 and 4 of the Michael adducts depend on the absence (3) or presence (4) of an aryl group in β position. The non‐benzylic 3 or its protonated or deprotonated form can cyclize via ester condensation to yield the “dibenzo‐bicyclo[3.2.2.]nonanones” 10b, c. Deprotonation of the anion 4 by excess AH− usually leads to fragmentation of the CCAr bond formed in the Michael addition. The overall result is a selective C = C reduction of cinnamonic acid derivatives and analogues: PhR′C = C → PhR′CH  CH. This fragmentation is hampered in the Michael addition adduct 4h with dimethyl benzylidenemalonate 2h probably due to the necessity of a pronounced conformational reorganization during the fragmentation step.
Novel Syntheses of 2,3,4,5‐Tetranor‐ and 6‐oxo‐Prostaglandins
Authors: Meese Claus O.
Published: July 2007

Two short synthetic routes to the major metabolites of prostaglandins in man are reported. First, the 2,3,4,5‐tetranorprostaglandins 1 and 2 are readily accessible by one‐carbon homologation of γ‐lactone 8 which involves the use of an ylide reagent, prepared from (1,3‐dithian‐2‐yl)triphenylphosphonium chloride (9), subsequent cyclization of thioketene S,S‐acetal 10 to spirotricyclic 11, and desulfurization to yield the required δ‐lactone 12. Second, 6‐oxoprostaglandins 3 and 4 are conveniently synthesized via α‐acylation of the enolates of γ‐lactones such as 22 followed by deprotection, hydrolysis, and decarboxylation of the resultant 3‐oxocarboxylic acids. Both approaches have been realized with the synthesis of deuterated, racemic analogues of the prostaglandin metabolites.
Reactions of Partially Acylated Aldohexopyranosides, VIII. A New Synthesis of the Tetradeoxydisaccharide in Avermectins
Authors: Rainer Hildegard , Scharf Hans‐Dieter , Runsink Jan
Published: July 2007

Methyl 4‐O‐benzyl‐3‐O‐methyl‐2‐O‐pivaloyl‐α‐L‐rhamnopyranoside (6) was prepared from L‐rhamnose in an improved synthesis in six steps (overall yield: 51%) and was used as the key building block. Acetolysis of 6 gave the glycosyl donor, 1,4‐di‐O‐acetyl‐3‐O‐methyl‐2‐O‐pivaloyl‐α‐L‐rhamnopyranose (7), which was coupled with the acceptor, methyl 3‐O‐methyl‐2‐O‐pivaloyl‐α‐L‐rhamnopyranoside (8), simply prepared by debenzylation of 6. The glycosylation reaction was carried out in the presence of trimethylsilyl triflate and led exclusively to the α‐linked disaccharide, methyl 4‐O‐(4‐O‐acetyl‐3‐O‐methyl‐2‐O‐pivaloyl‐α‐L‐rhamnopyranosyl)‐3‐O‐methyl‐2‐O‐pivaloyl‐α‐L‐rhamnopyranoside (9). Selective removal of the acetate group and irradiation of the 2,2′‐dipivaloates gave directly the tetradeoxydisaccharide, methyl 4‐O‐(α‐L‐oleandrosyl)‐α‐L‐oleandropyranoside (11). Irradiation of compound 8 afforded methyl α‐L‐oleandropyranoside (11). Irradiation of compound 8 afforded methyl α‐L‐oleandropyranoside (12) as the only product in 80% yield.
Asymmetric Induction in the Epoxidation of Alkenyl Glycosides of Tri‐O‐acetyl‐N‐acetyl‐β‐D‐glucosamine
Authors: Peter Martin G. , Boldt Peter‐c. , Petersen Stefan
Published: July 2007

The reaction of alkenyl glycosides 2a–2c with MCPBA gives diasteroisomeric mixtures of epoxides 3 and 4. The asymmetric induction decreases in the order 2a ≫ 2b > 2c. The absolute configuration of epoxyalkyl glycosides is determined by correlation with (R)‐glycerinaldehyde in an independent synthesis of 3a and 3c.
Eine kurze, effektive Synthese von rac‐Deplanchein
Authors: Rosemund Peter , Hosseini‐Merescht M.
Published: July 2007

A Short and Effective Synthesis of rac‐Deplancheine

Tryptamine and dimethyl methoxyallylidenemalonate (1) react to give the divinylogous urethane 2, which yields by reaction with acroleine under acid catalysis the β‐carboline 3a. Reductive decarboxylation gives the target compound deplancheine (4a) in excellent overall yield.
Amphiphilic Carbohydrate‐Based Mesogens, VIII. A Facile Synthetic Route to Mesogenic L‐ribo‐1,2,3,4‐alkanetetrols
Authors: Dahlhoff Wilhelm V.
Published: July 2007

The Wittig olefinations of 2,3‐O‐isopropylidene‐D‐ribofuranose (1) with two equivalents of alkylidenetriphenylphosphorane (alkylidene: hexylidene — undecylidene) followed by hydrogenation catalyzed by palladium on carbon and subsequent deprotection yield (2R,3S,4S‐(“L‐”ribo)‐1,2,3,4‐alkanetetrols 5. These amphiphiles form the smectic A mesophase on melting. However, when 1 is heated with one equivalent of the alkylidenetriphenylphosphoranes for longer periods, (2R,3S,4R)‐(“D‐lyxo”)‐1,2,3,4‐alkanetetrol‐type products 4 predominate.
Wittig Olefination of Unprotected Carbohydrates with a Semistabilized Ylide
Authors: Henk Thomas , Giannis Athanassios , Sandhoff Konrad
Published: July 2007

The Wittig reaction of unprotected sugars 1a–d with benzylidenetriphenylphosphorane leads to open‐chain derivatives 2a–d. Ozonolysis of these derivatives gives the parent compounds.
Steroids, XLV. Neighbouring Group Participation, XII. Decomposition of (Z)‐16‐Amidomethylene‐17β‐hydroxysteroids Mediated by Neighbouring Group Participation
Authors: Vincze Somlai Schneider Dombi Mák Irén Csaba Gyula György Marianna
Published: July 2007

The sodium tetrahydroborate reduction of 16‐<[acetyl(alkyl)‐amino]methylene>‐17‐ketosteroids 1aa, 2aa and 2ba affords (Z)‐16‐ and (E)‐16‐<[acetyl(alkyl)amino]methylene>‐17β‐hydroxysteroids (Z)‐3, (E)‐3, (Z)‐4b, (Z)‐4a, (Z)‐5c and (E)‐5a. The N‐acetyl group of the (Z) isomers (Z)‐3, (Z)‐4b, and (Z)‐5c migrates to the 17β‐hydroxyl in inert solvents, and the products suffer secondary transformation into unsaturated aldehydes 6 and 9a; intermediate 8 has been isolated. The (E) isomers (E)‐3, and (E)‐5a do not change, even not under more drastic conditions.