bluuebunny/crossref_metadata_2025 huggingface dataset:
The Dipeptide Antibiotic N‐Valyl‐dihydroxyhomoproline: Isolation, Characterization, and Antimicrobial Activities
Authors: Kern Armin , Bovermann Günter , Jung Günther , Wanning Martin , Zähner Hans
Published: July 2007

The dipeptide antibiotic N‐valyl‐dihydroxyhomoproline (Val‐Dhp, 1) was isolated from the culture filtrate of Streptomyces antibioticus ssp. antibioticus Tü 1718 by gel chromatography and HPLC. The purification, chemical, and spectroscopic characterization were hampered by complex equilibria between different forms of the highly hydrophilic antibiotic. The dipeptidic antibiotic crystallizes in thin needles. 1 consists of N‐terminal L‐valine coupled to a new dihydroxyimino acid related to L‐hydroxyproline. The results of 1H NMR, 13C NMR, mass (GC‐MS, FD) spectra and the comparison with synthetic L‐valyl‐L‐hydroxyproline are consistent with the proposed structure 2‐[1‐(2‐amino‐3‐methyl‐1‐oxobutyl)‐4‐hydroxy‐2‐pyrrolidinyl]‐2‐hydroxyetha‐noic acid. N‐Valyl‐dihydroxyhomoproline is active against Escherichia coli K 12, Corynebacterium spec., and Serratia marcescens.
Reactions of Acenaphthylene‐1,2‐quinone Monoxime with Some Phosphorus Ylides. ‐ Synthesis of Acenaphtho [1,2‐x]‐Fused Compounds
Authors: Papageorgiou Georgios , Nicolaides Demetrios , Stephanidou‐Stephanatou Julia
Published: July 2007

By applying a Wittig reaction on the monoxime 1 with phosphorus ylide 2 the oximes 3(I,II) are isolated whereas with ylide 5 the pyridine derivative 8 is obtained. Reaction of 1 with the bis‐salt 9 in the presence of lithium ethoxide gives through a Wittig and a “Wittig‐type” reaction the fluoranthene 11. Hydrogenation of compound 3(I) to oxime 12 and thermal cyclization of the latter leads to the formation of the polycyclic compound 15.
Synthese und Eigenschaften von 1‐Thia‐2‐cyclooctin
Authors: Stavridou Evaggelia , Schuhmacher Hans , Meier Herbert
Published: July 2007

Aus 6‐Bromhexansäure (1) wird über das Keton 9 mit der Selenadiazol‐Methode die Titelverbindung 14 hergestellt. 14 besitzt eine gespannte und polarisierte Dreifachbindung, was sich in einer ungewöhnlich hohen Reaktivität bemerkbar macht. Außer der Addition von Wasser und Ethanol zu 9 bzw. 29 werden die Cycloadditionen mit Tetraphenylcyclopentadienon zu 16, mit Diazomethan zu 32 und 33 und mit Schwefelkohlenstoff zu 35 und 36 besprochen. 35 und 36 bilden mit TCNQ die tiefschwarzen Komplexe 37, 38. Als Nebenprodukte werden bei der thermischen Selenadiazol‐Fragmentierung die 1,4‐Diselenine 21, 22, die Selenophene 23–25 und die 1,3‐Diselenole 27, 28 erhalten.
Heteroyohimban‐Analoga aus 3‐Acetyl‐7,12‐dihydro‐2‐methyl‐6H‐indolo‐[2,3‐a]chinolozinium‐chlorid
Authors: Teuber Hans‐Joachim , Quintanilla‐Licea Ramiro
Published: July 2007

In dem aus Tryptamin‐hydrochlorid und Acetylacetaldehyd‐dimethylacetal gebildeten 3‐Acetyl‐7,12‐dihydro‐2‐methyl‐6H‐indolo[2,3‐a]chinolizinium‐chlorid (1a) und seinem Acetal 1b wird die Methyl‐Seitenkette durch Umsetzung mit Carbonyl‐Verbindungen kondensiert. Benzaldehyd und Furfural führen ausgehend von 1b zu den Stilbazolen 4a–d, nach Hydrierung von Ring C zu den Tetrahydropyridinen 5a–c. Mit Hydrat‐bildenden Carbonyl‐Verbindungen wie Chloral, Mesoxalsäure‐diethylester und Ninhydrin bleibt die Wasser‐Abspaltung aus (6–8, 10, 12), und es kommt ausgehend von 1a unter Beteiligung der Acetyl‐Seitenkette zur Schließung des Heteroyohimban‐ähnlichen Ringes E (9, 11, 13).
Pheromone Synthesis, CXIII. Synthesis of the Enantiomers of (3Z,6Z)‐cis‐9,10‐Epoxy‐1,3,6‐henicosatriene and (3Z,6Z)‐cis‐9,10‐Epoxy‐1,3,6‐icosatriene, the New Pheromone Components of Hyphantria cunea
Authors: Mori Kenji , Takeuchi Tadashi
Published: July 2007

The synthesis of (9S,10R)‐epoxytrienes 1 and 2 as well as their antipodes was achieved employing the asymmetric Sharpless epoxidation as the key step.
Synthesis of Tertiary Alcohol Carbamates
Authors: Nikiforov Alexej , Jirovetz Leopold , Buchbauer Gerhard
Published: July 2007

n‐Butyllithium has been used to prepare a large number of carbamates of some lower tertiary alcohols, especially of tertiary terpene alcohols, like linalool (5), 1‐terpineol (6), cedrol (9), and patchoulol (8) via the corresponding alkoxides. The reaction time in each case was less than an hour, and the isolated yields of most of the carbamates were higher than 85%. The carbamates of synthetic (±)‐ and genuine (‐)‐patchoulol (8) were investigated by GC with chiral phases in order to determine their optical purity and degree of racemization. The racemization of (‐)‐patchoulol after derivatization is less than 3 percent.
A New Route to Pyrazolo[3,4‐e]‐1,2,4‐triazines
Authors: Sadek Kamal Usef , Abouhadid Khalid , Elghandour Ahmed Hafez Hussein
Published: July 2007

A new method leading to pyrazolo[3,4‐e]‐1,2,4‐triazines 5, 8, and 9 by reaction of acyl cyanides with the 3‐substituted 4‐phenylhydrazono‐5‐pyrazolamines 1a–d is reported.
[3.3.3]Propelladiendicarbonitrile
Authors: Quast Helmut , Röschert Horst , Peters Eva‐Maria , Peters Karl , Schnering Hans Georg Von
Published: July 2007

Das 3,7‐Diketon 5 reagiert mit 4‐Chlorthiophenol in Gegenwart von Titan(IV)‐chlorid/Triethylamin zu gleichen Mengen der Bis(vinylsulfide) C2/C5‐6 (65% Ausb.), die unter Trifluoressigsäure‐Katalyse zu einem (3:2)‐Gemisch äquilibriert werden. Oxidation von C2/C5‐6 mit Natriumperborat‐tetrahydrat in Essigsäure ergibt fast quantitativ die Bis(vinylsulfone) C2/C5‐7. Diese liefern mit Kaliumcyanid auf Aluminiumoxid in siedendem 2‐Methyl‐2‐butanol ein Gemisch der α,β‐ungesättigten Dinitrile 1b, 11, 13 und 14, die chromatographisch getrennt werden So werden auch die Zwischenstufen 8 und 10 sowie Folgeprodukte von 1b und 11, nämlich die Trinitrile 9 und 12, isoliert. das Dinitril 1b wird mit N‐Bromsuccinimed zu einem Gemisch von endo‐15, exo‐15, endo,endo‐16, endo,exo‐16 und 17 bromiert, das größtenteils chromatographisch getrennt wird. Das endo‐Bromdinitril endo‐15 reagiert mit Kaliummethanolat in Methanol zum exo‐Methoxydinitril 18. Die Konfiguration der Dinitrile endo‐15, endo,endo‐16 und 18 wird durch NOE‐Differenz‐Spektren und Röntgenstrukturanalyse bewiesen.
Über die Dimerisierung von N‐(Arylmethylen)dehydroalaninestern
Authors: Wulff Günter , Böhnke Helmut , Steigel Alois , Klinken Heinz Theo , Lindner Hans Joerg
Published: July 2007

N‐(Arylmethylen)dehydroalaninester sind hochreaktive Verbindungen. Sie dimerisieren unter [4+2]‐Cycloaddition (Diels‐Alder‐Reaktion) zu rac‐3,4,5,6‐Tetrahydropyridin‐Derivaten 2, die unter geeigneten Bedingungen isoliert werden können. In Lösung tautomerisieren die Dimeren 2 zu Enaminen 3, die schnell intramolekular zum Bicyclus 4 reagieren. Diese 3,6‐Diazabicyclo‐[3.2.1]oct‐2‐en‐Derivate 4 werden diastereoselektiv gebildet. Ihre Struktur wurde durch Röntgenstrukturanalyse geklärt. Die bicyclischen Diaminodicarbonsäureester 4 stellen die stabilen Endprodukte der gesamten Reaktionsfolge dar.
Kinetische Racematspaltungen ausgehend von rac‐Alkoholen oder rac‐Carbonsäurehalogeniden unter Mitwirkung optisch aktiver Induktorbasen
Authors: Weidert Peter J. , Geyer Ekkehard , Horner Leopold
Published: July 2007

Bei der Umsetzung eines Moläquivalents achiraler Carbonsäurehalogenide mit zwei Moläquivalenten rac‐Alkoholen entstehen unter Mitwirkung von einem Moläquivalent einer optisch aktiven Induktorbase (tertiäres Amin) partiell optisch aktive Ester sowie partiell optisch aktive Alkohole in zum Teil hoher optischer Reinheit (60 – 70%). Der im Ester gebundene Anteil an Alkohol sowie der nicht umgesetzte Alkohol haben entgegengesetzte Konfiguration. Der Induktionsgrad ist ähnlich hoch, wenn man zwei Moläquivalente eines rac‐Carbonsäurehalogenids mit je einem Moläquivalent eines achiralen Alkohols und einer Induktorbase umsetzt. Der Carbonsäureanteil im Ester und die freie Säure haben entgegengesetzte Konfiguration. Die optischen Induktionen werden beeinflußt a) durch die Art der mit den Reaktionszentren verknüpften Liganden, b) durch die relativen Mengen der Reaktionspartner, c) durch das Lösungsmittel und d) durch die Temperatur.
Potential H1‐Antihistaminic Drugs: Synthesis of 4‐[(2,3‐Dihydro‐2‐oxo‐1H‐benzimidazol‐1‐yl)alkoxycarbonyl]‐1‐(diphenylmethyl)piperazines by Selective Monoalkoxycarbonylation of α,ω‐Dichloroalkanes by Phase‐Transfer Catalysis
Authors: Gómez‐Parra Vicente , Jiménez Mercedes , Sánchez Félix , Torres TomáS
Published: July 2007

The synthesis of a series of new 4‐[(2,3‐Dihydro‐2‐oxo‐1H‐benzimidazol‐1‐yl)alkoxycarbonyl]‐1‐(diphenylmethyl)piperazines 2 by phase‐transfer catalysed monoalkoxycarbonylation of α,ω‐dichloroalkanes is described. Compounds 2 are related to oxatomide1) (1) and are potential histamine‐H1 antagonists. A study on the regioselective preparation of substituted 1,3‐dihydro‐1‐isopropenyl‐2H‐benzimidazol‐2‐ones (5) was also carried out.
Photochemical Reactions of 1‐Alkyl‐4,6‐diaryl‐2(1H)‐pyrimidinones in the Presence of Amines
Authors: Nishio Takehiko , Kato Michiyo , Kashima Choji
Published: July 2007

Irradiation of 1‐alkyl‐4,6‐diaryl‐2(1H)‐pyrimidinones 1 in the presence of aliphatic amines gave the CC‐bonded 1:1 adducts and/or the reduced dihydropyrimidinones, while irradiation of 1 in the presence of aromatic amines gave the 1:1 adducts exclusively. The photoadditions of amines to 1 can be explained by a sequential electron/proton transfer mechanism.
Chirale Ferrocenylalkylamine aus dem natürlichen „Chiral‐Pool”︁
Authors: Siglmüller Franz , Herrmann Rudolf , Ugi Ivar
Published: July 2007

Ausgehend von den chiralen Terpenen α‐ und β‐Pinen sowie Campher werden enantiomerenreine α‐Ferrocenylalkylamine ohne Enantiomerentrennungen dargestellt. Die verschiedenen Umlagerungen der als Zwischenprodukte auftretenden α‐Ferrocenylalkylcarbokationen werden untersucht und für die Synthese und Konfigurationszuordnungen ausgenutzt.
Synthesis and Stereochemistry of the Dibromides of Exocyclic α,β‐Unsaturated Ketones
Authors: Tóth Gábor , Janke Frank , Lévai Albert
Published: July 2007

The dibromides 7–12 have been synthesized by addition of bromine to exocyclic α,β‐unsaturated ketones 1–6. The relative configurations and the stereochemistry of the products have been determined by NMR methods. Bromination of 3‐benzylideneflavanone (3) and its thio analogue 5 proved to be highly stereoselective.
Regioselektive Benzylierungen an Hydroxyalkyl‐3‐morpholinonen
Authors: Danklmaier Johann , Hönig Helmut
Published: July 2007

Hydroxyalkylmorpholinone vom Typ 2 können je nach Reaktionsbedingungen am Amidstickstoff, an der Hydroxyl‐Gruppe oder am Carbonylsauerstoff benzyliert werden. Beim Versuch der Benzylierung mittels Trichloracetimidsäure‐benzylester (15) kommt es teilweise zu einer bis jetzt nicht beschriebenen „Umimidatisierung”︁. Alle Produkte werden durch NMR‐Spektroskopie eindeutig identifiziert.
Pheromone Synthesis, CXVI Conversion of the Enantiomers of Sulcatol to the Enantiomers of cis‐Pityol, a Volatile Compound from the Elm Bark Beetle Pteleobius vittatus
Authors: Mori Kenji , Puapoomchareon Prapai
Published: July 2007

Pure cis‐(2R,5R)‐pityol (1) was synthesized from ethyl (R)‐3‐hydroxybutanoate (3) via cyclization of (R)‐sulcatol (2) with tert‐butyl hydroperoxide in the presence of a vanadium catalyst. In the same manner, cis‐(2S,5S)‐pityol (1) was synthesized from (S)‐3 via (S)‐2.
Reactions of Pyrano[3,4‐b]indol‐3‐ones with Dienophiles: Consecutive [4 + 2] Cycloaddition/Cycloreversion/1,2 Elimination
Authors: Pindur Ulf , Erfanian‐Abdoust Houshang
Published: July 2007

Methylpyrano[3,4‐b]indol‐3‐ones 1 react with selected dienophiles (as acetylene equivalents) in a consecutive Diels‐Alder/cycloreversion/1,2 elimination reaction sequence to furnish the 1‐methyl‐ and 1,4‐dimethylcarbazoles 4.
Total Synthesis of the Azoxy Antibiotic Jietacin A
Authors: Giencke Wolfgang , Ort Oswald , Stark Herbert
Published: July 2007

The total synthesis of the azoxy antibiotic jietacin A (1) has been accomplished starting from cyclooctanone via a protected 14‐methyl‐8‐oxopentadecylamine.
3a,8b‐Dihydro‐7‐methoxy‐8b‐(trifluoromethyl)‐2H‐indeno[1,2‐b]furan‐2,4(3H)‐dione
Authors: Ukerun Sylvester Ohwevwo
Published: July 2007

3‐(Methoxycarbonyl)‐4‐(3‐methoxyphenyl)‐4‐(trifluoromethyl)‐4‐butanolide (4) was synthesised from 3‐methoxyphenyl trifluoromethyl ketone (1). Hydrolysis of the lactone ester 4, followed by treatment with polyphosphoric acid, led to an intermediate lactone acid 3, which on heating with PCl5 gave the indeno‐[1,2‐b]furandione 5.
Reaktionen der Methylencyclopropane, XI Asymmetrische Nickel(0)‐katalysierte [3 + 2]‐Cycloadditionen von Methylencyclopropanen mit chiralen Acrylsäure‐Derivaten
Authors: Binger Paul , Brinkmann Axel , Roefke Petra , Schäfer Bernd
Published: July 2007

Bei der Nickel(0)‐katalysierten Codimerisierung von Methylencyclopropan (1a) oder 2,2‐Dimethylmethylencyclopropan (1b) mit den chiralen Acrylsäure‐Derivaten 2a–2f werden die 3‐Methylencyclopentancarbonsäureester bzw. ‐amide (3a–3f, 4a–4c) in guten Ausbeuten gewonnen, wobei, in Abhängigkeit von den sterischen Gegebenheiten der chiralen Hilfsstoffe, Diastereomerenüberschüsse bis zu 98% de erzielt werden. Einige Verbesserungen in der Darstellung der optisch reinen Hilfsgruppen werden ebenfalls beschrieben.
Oxidation of Organic Diselenides with Hydrogen Peroxide to Alkane‐ and Areneseleninic Acids and Selenium‐Containing Heterocycles
Authors: Kloc Krystian , Mlochowski Jacek , Syper Ludwik
Published: July 2007

A convenient way is reported for the oxidation of organic diselenides 1, 3 to organoseleninic acids 2, 4 which were isolated and identified as pure compounds. Some ortho‐substituted phenyl diselenides 3d–f underwent oxidative cyclization, and the selenium‐containing heterocyclic compounds 5 were obtained.
Synthese von bis(trifluormethyl)substituierten Pyrethroiden
Authors: Mack Helmut , Hanack Michael
Published: July 2007

Es wird über eine Methode zur Darstellung von 1,1‐bis(trifluor‐methyl)substituierten Pyrethroiden berichtet. Dazu werden 1,1‐bis(trifluormethyl)substituierte Olefine 9 auf einfache Weise durch Reaktion der Aldehyde 17 mit 2,2‐Dichlorhexafluorpropan (16) und Triphenylphosphan dargestellt und mit (Ethoxycarbonylmethylen)dimethylsulfuran (10) in die 2,2‐Bis(trifluormethyl)cyclo‐propancarbonsäureester (5a, g, h, i) übergeführt. Ausgehend von 4,4,4‐Trifluor‐3‐(trifluormethyl)‐2‐butenal‐diethylacetal (9c) wird durch Umsetzung mit dem Sulfuran 10 der 3‐Formyl‐2,2‐bis(trifluormethyl)cyclopropancarbonsäure‐ethylester (Hexafluorcaronaldehydsäure‐ethylester) (5c) erhalten. 5c stellt eine wichtige Zwischenstufe zur Darstellung der bis(trifluormethyl)substituierten Pyrethroidester 5d–f dar. Die Hydrolyse der Esterfunktion in den Pyrethroidestern 5a, h liefert die Carbonsäuren 6a, b, die über die Säurechloride 38 und Umsetzung mit α‐Cyan‐3‐phenoxy‐benzylalkohol (39) in die entsprechenden Pyrethroidester 7a, b übergeführt werden. 1‐(4‐Chlorphenyl)‐3,3,3‐trifluor‐2‐(trifluor‐methyl)‐1‐propen (9g) reagiert mit Aceton‐cyanhydrin zum Nitril 47. Nach Überführung in die Carbonsäure 48 und das Säurechlorid 49 wird dieses mit α‐Cyan‐3‐phenoxybenzylalkohol (39) zum Hexafluorfenvalerat (8) umgesetzt.
Synthese von (trifluormethyl)substituierten Pyrethroiden
Authors: Nägele Ulli M. , Hanack Michael
Published: July 2007

1,1,1‐Trifluoraceton (2) reagiert mit den Phosphoryliden 1 zu den (trifluormethyl)substituierten Olefinen 3a–d, wobei überwiegend die E‐Isomeren entstehen. 3‐(Trifluormethyl)‐2‐butennitril (3a) wird mit (Ethoxycarbonylmethylen)dimethylsulfuran (4a) zu 3‐Cyan‐2‐methyl‐2‐(trifluormethyl)cyclopropancarbonsäure‐ethylester (5a) umgesetzt, wobei vier Diastereomere entstehen. 5a läßt sich mit Tri‐n‐hexylsilan zum 3‐Formyl‐2‐methyl‐2‐(trifluormethyl)cyclopropancarbonsäure‐ethylester (Trifluorcaronaldehydsäure‐ethylester) (6) reduzieren. Aus dem Aldehyd 6 werden die mono(trifluormethyl)substituierten Pyrethroidester 7a, 7b und 7c gewonnen. 7a wird in das Pyrethroid 7f übergeführt.
Marine Bakterien, I. Synthese von Pentabrompseudilin, einem cytotoxischen Phenylpyrrol aus Alteromonas luteo‐violaceus
Authors: Laatsch Hartmut , Pudleiner Heinz
Published: July 2007

Eine neue Synthese für 2,3,4‐Tribrom‐5‐(3,5‐dibrom‐2‐hydroxyphenyl)pyrrol (1a, Pentabrompseudilin), einem antibakteriell, enzyminhibitorisch und cytotoxisch wirksamen Inhaltsstoff aus dem marinen Bakterium Alteromonas luteo‐violaceus, wird beschrieben. Für die Untersuchung von Struktur‐Wirkungs‐Beziehungen werden zahlreiche weitere 2‐Phenylpyrrole in einer Reaktionsfolge hergestellt, deren Schlüsselschritte die Grignard‐Reaktion von 2‐(1,3‐Dioxan‐2‐yl)ethylmagnesiumbromid (9d) mit Benzoylchloriden zu γ‐Phenyl‐γ‐ketoaldehyden 24 und deren Paal‐Knorr‐Cyclisierung sind.
Stereoselective Synthesis of Alcohols, XXXII. Synthesis of the Prelog‐Djerassi Aldehyde and of a C‐1/C‐9 Segment of 6‐Deoxyerythronolide
Authors: Hoffmann Reinhard W. , Ladner Wolfgang , Ditrich Klaus
Published: July 2007

Stereoselective (>95%) chain extension of the Masamune aldehyde 1 to the lactone 9 was achieved using the chiral pentenylboronate 8 as reagent. The lactone 9 was converted into the Prelog‐Djerassi aldehyde 2. Its subsequent reaction with the chiral pentenylboronate 8 resulted in the desired lactone 19. This reaction was, however, complicated by partial epimerisation of the aldehyde 2.
Radical Additions in Aqueous Medium: Direct Synthesis of 5‐Allyl‐Substituted γ‐Lactones from Allylic Bromides/Zinc and Methyl γ‐Oxocarboxylates
Authors: Kunz Thomas , Reißig Hans‐Ulrich
Published: July 2007

Following a procedure published by Luche, 5‐allyl‐substituted γ‐lactones 2a–2d are prepared in good yield from methyl γ‐oxocarboxylates 1a–1c and allyl bromides/zinc dust in aqueous medium. The diastereoselectivity of this allylation reaction is compared to that of Lewis acid promoted additions of allyltrimethylsilane to chiral aldehydes.
Conformation of Antamanide
Authors: Kessler Horst , Bats Jan Willem , Lautz Jörg , Müller Arndt
Published: July 2007

The conformation of the cyclic decapeptide antamanide (1) in CDCl3 solution was determined by means of NMR‐spectroscopic methods. Distances obtained from 40 negative NOE values at 500 MHz at low temperature were used as constraints in calculations with the GROMOS molecular dynamics program package to elucidate the most stable backbone conformation in solution. It turned out that there is a fast conformational equilibrium between up to four conformations which differ in a flip about φ and ψ around the two amide bonds Ala4–Phe5 and Phe9–Phe10. Side chain conformations were determined using homo‐ and heteronuclear coupling constants. Carbon relaxation times provide information about the internal flexibility of 1. Three new antamanide derivatives in which Pro3, Pro7, or Pro8 have been substituted by γ‐thiaproline (Thz) were synthesized and crystallized from acetone/water. The X‐ray analyses of these Thz derivatives demonstrate that in the presence of water antamanide adopts a preferred structure which includes four water molecules for building up a compact hydrogen‐bonded structure, which differs from the conformation in chloroform sulution.
Zur Synthese und Dimroth‐Umlagerung von 4‐(Dialkylamino)‐2H‐1,3,5‐oxadiazin‐2‐thionen
Authors: Spitzner Roland , Andersch Jörg , Schroth Werner
Published: July 2007

Concerning the Synthesis and the Dimroth Rearrangement of 4‐(Dialkylamino)‐2H‐1,3,5‐oxadiazine‐2‐thiones

The title compounds 3 are readily obtained by reaction of N,N‐dialkylchloroformamidines 2 with potassium thiocyanate. The amidines 2 can be prepared profitably from isocyanide dichlorides 1 with the aid of N‐(trimethylsilyl)dialkylamines. The thiones 3 behave very sensitively towards acids and are rearranged completely to 4‐(dialkylamino)‐2H‐1,3,5‐thiadiazin‐2‐ones 4 by treatment with acetic acid.
Synthesis of (‐)‐Biopterin
Authors: Mori Kenji , Kikuchi Haruhiko
Published: July 2007

The synthesis of (‐)‐biopterin (1) was accomplished by employing (1S,2S)‐1‐(2‐furyl)‐2‐(trityloxy)‐1‐propanol (6), derived from ethyl (S)‐lactate, as building block for the side chain.
Eigenschaften und Reaktionen substituierter 1,2‐Thiazetidin‐1,1‐dioxide: 2‐und/oder 4‐silylierte 1,2‐Thiazetidin‐1,1‐dioxide
Authors: Müller Martin , Meyle Eberhard , Otto Hans‐Hartwig , Paulus Erich F. , Plagge Herbert
Published: July 2007

Durch Silylierung unter verschiedenen Bedingungen und in Abhängigkeit von den molaren Verhältnissen der Reaktanden können aus 1,2‐Thiazetidin‐1,1‐dioxid (β‐Sultam, 1) alle denkbaren an N‐ und C‐4 silylierten Produkte 2–11 erhalten werden. Die 2,3‐disubstituierten β‐Sultame 16 und 19 werden an C‐4 silyliert, wobei Disilylierung bevorzugt ist. Von 2d wird die Struktur durch eine Röntgenstrukturuntersuchung bei −130°C geklärt. Die Stabilität und einige spektroskopische Eigenschaften werden diskutiert.
Carboxy‐ and Cyano‐Hydroxylation of Alkenes. Synthesis of 3‐Hydroxy‐4‐amino Acids and Butyrolactones via the Isoxazoline Route
Authors: Halling Karen , Thomsen Ib , Torssell Kurt B. G.
Published: July 2007

Dichloro‐ and dibromoformaldoximes are useful 1,3‐dipolar cycloaddition reagents. They are conveniently preparated in situ, in high yields by dihalogenation of glyoxalic acid aldoxime with N‐bromo‐ and N‐chlorosuccinimide or tert‐butyl hypochlorite. Dehydrohalogenation with potassium hydrogen carbonate in the presence of alkenes gives 3‐halo‐isoxazolines in a one‐pot reaction. Reduction with iron pentacarbonyl gives β‐hydroxynitriles. Methoxylation and catalytic reduction give β‐hydroxy esters. Allyl alcohols and allylamines are transformed with halonitrile oxides into butyrolactones (DL‐angelica lactone) and DL‐3‐hydroxy‐4‐amino acids (carnitine, 4‐amino‐3‐hydroxybutyric acid), respectively. The lactonization is best effected by heating the γ‐silyloxy ester in acetic acid with potassium hydrogen sulfate as catalyst. A synthesis of N‐Boc‐dihydromuscimol is described.
Neuartige Umlagerungen in der Pregnanseitenkette
Authors: Annen Klaus , Hofmeister Helmut , Laurent Henry , Hoyer Georg‐Alexander
Published: July 2007

17‐Acetoxy‐21‐(acetylthio)‐4‐pregnen‐3,20‐dion (3) reagiert mit einem großen Überschuß an Natriumazid in Methanol zu einem Gemisch der Umlagerungsprodukte Etiansäure‐methylester 11 und Spirodithiolanon 12. Der Reaktionsablauf wird in Abhängigkeit von Reaktionstemperatur und Lösungsmittel untersucht. Um weitere Einblicke in einen möglichen Umlagerungsmechanismus zu gewinnen, werden die Verbindungen 4–10, die 6α‐Methyl‐ und die D‐Homoverbindungen 13b und 13d als Modellsubstanzen synthetisiert und den Umlagerungsbedingungen unterworfen.
Strukturanalyse von Steroid‐17‐spiro‐dithiolanonen
Authors: Hoyer Georg‐Alexander , Annen Klaus , Cleve Gerhard , Herrmann Christoph , Hofmeister Helmut , Laurent Henry , Sheldrick William S.
Published: July 2007

Mit IR‐, CD‐, 1H‐NMR‐ und Massen‐Spektrometrie sowie Röntgenstrukturanalyse wurden die Strukturen von sieben Androstan‐17‐spiro‐3′‐(1′,2′‐dithiolan)‐4′‐onen bestimmt. Alle Verbindungen besitzen (17R)‐Konfiguration (17β‐CO, 17α‐S). Gleiche Stereochemie (17aR) kommt auch einer entsprechenden D‐Homoverbindung zu.
A Novel Example of a 7‐exo‐trig Heterocyclization
Authors: Martían Nazario , Quinteiro Margarita , Seoane Carlos , Soto José L.
Published: July 2007

We report that the open‐chain hydrazide 12, resulting from Knoevenagel condensation of cyanoacetohydrazide (10) with 3‐benzylidene‐2,4‐pentanedione (11), undergoes a 7‐exo‐trig heterocyclization, leading to the 1,3‐diazepinone 14.
Total Synthesis of [3aS‐(3aα,9aα,9bβ)]‐3a,4,5,9,9a,9b‐Hexahydro‐3a,6‐dimethyl‐1H‐benz[e]indene‐3,7(2H,8H)‐dione and Derivatives, Building Blocks for the Synthesis of Glucocorticoids
Authors: Daniewski Andrzej Robert , Piotrowska Emilia , Wojciechowska Wanda
Published: July 2007

The 1H‐benz[e]indenes 17–21, building blocks for the synthesis of steroids, were synthesized by coupling the silyl enol ethers 5 or 6 with ethylene acetals 7,8 of α,β‐unsaturated ketones, followed by cyclization under basic or acidic conditions.
Die Konfiguration der 1,2‐Diketon‐hydrazon‐oxime
Authors: Gnichtel Horst , Töpper Bernhard
Published: July 2007

Die Konfiguration der 1,2‐Diketon‐(Z)‐hydrazon‐(E)‐oxime 3a–c wurde durch Ringschluß mit Formaldehyd zu den 1,2,4‐Triazin‐4‐oxiden 5a–c und den tautomeren 4‐Hydroxy‐1,2,4‐triazinen 6a–c sowie durch Beckmann‐Reaktion zu 1,2,4‐Triazolen 8a–c bewiesen. Aus dem Benzil‐(Z)‐hydrazon‐(Z)‐oxim 4a wird ein 1,2,5,6‐Oxatriazepin‐Derivat 9a erhalten.
Naturstoffe aus Arzneipflanzen, XXV Isolierung und Strukturaufklärung neuer Inhaltsstoffe aus dem sodaalkalischen Extrakt von Picrorhiza kurrooa
Authors: Weinges Klaus , Schick Hartmut , Neuberger Karl , Ziegler Hans Jürgen , Lichtenthäler Jochen , Irngartinger Hermann
Published: July 2007

Aus dem sodaalkalischen Extrakt von Picrorhiza kurrooa wurden zehn Verbindungen als Acetate kristallin isoliert. Während das Pentaacetyl‐6′‐cinnamoylcatalpol, Hexaacetyl‐6‐vanilloylcatalpol und Hexaacetylcatalpol direkt mit authentischen Proben identifiziert werden konnten, wurden die Strukturen der Verbindungen 1–6 und 8 durch Röntgenstrukturanalyse bzw. spektroskopisch ermittelt. Die acetylierten Cucurbitacin‐glucoside 3–5 weisen gegenüber den natürlichen Cucurbitacinen eine verkürzte Seitenkette auf. Da sie im Neutralextrakt chromatographisch nicht nachgewiesen werden konnten, müssen 3–5 erst bei Extraktion bzw. Aufarbeitung entstehen und Artefakte darstellen. Als einziges acetyliertes C30‐Cucurbitacin‐glucosid konnte (20R)‐3β,16α,20,25‐Tetrahydroxy‐2β‐(β‐D‐tetraacetylglucopyranosyloxy)‐10α‐cucurbit‐5‐en‐22‐on (8a) kristallin erhalten werden.
Synthesis of Polymerizable Hexose Derivatives
Authors: Koßmehl Gerhard , Volkheimer Jürgen
Published: July 2007

Polymerizable esters of methacrylic and acrylic acid with di‐O‐isopropylidenehexoses as alcohol components have been synthesized.
Reaction of Some Cyclic Dienamines of Carbothioic Acid Anilides with Malononitrile
Authors: Bogdanowicz‐Szwed Krystyna , Rys Barbara
Published: July 2007

Morpholino enamines 1,2, and 3 of 2‐(cyclopentylidene)‐1‐cyclopentanone, 2‐(1‐cyclohexenyl)‐1‐cyclohexanone, and 2‐(cycloheptylidene)‐1‐cycloheptanone, respectively, react with aryl isothiocyanates to yield 1‐cycloalkene‐1‐carbothioic acid anilides 4, 5, and 6, respectively. Compounds 4 and 5 react with malononitrile to give the hexahydroisoquinolines 9 and the cyclopenta[c]pyridine 11, respectively.
Facile Reductive Cleavage of Oximes with a Low‐Valent Titanium Reagent
Authors: Balicki Roman , Kaczmarek Lukasz , Malinowski Marek
Published: July 2007

The application of the TiCl4/SnCl2 reagent system in the reductive deoximation of various ketoximes and aldoximes under mild conditions is reported. The corresponding carbonyl compounds were formed in high yields.
Enantiomerically Pure Building Blocks from Sugars, 10 2,3‐Dihydropyranones with Contiguous Chiral Centers: Practical Routes for Their Aquisition and Evaluation of their Reaction Potential
Authors: Lichtenthaler Frieder W. , Nishiyama Shigeru , Weimer Thomas
Published: July 2007

A practical, large‐scale adaptable four‐step procedure has been developed for the conversion of D‐glucose into pyranoid enediolone esters with (R,R)‐configuration in contiguous chiral centers, involving hydrolysis of the readily accessible bis‐acetonide of α‐D‐ribo‐hexos‐3‐ulose (12) and base‐mediated acylation. The sequence provides the acetyl (3), benzoyl (4) and pivaloyl (6) dihydropyranones in overall yields well exceeding 40%, whilst the maltose‐derived glucosyloxy‐substituted analogue 11 is accessible even more efficiently (69%) by low‐temperature benzoylation followed by DMSO/acetic anhydride treatment. – With the tribenzoate 4 as a model simply feasible addition reactions of preparative interest were evaluated, resulting in a unique transfer of chirality from one side of the pyranoid ring to the other upon treatment with methanol/K2CO3 (4 → 23), in C‐branching (4 → 18) or C‐extension (4 → 19), and in an unusual photoaddition of acetone to an O,O‐isopropylidene‐dihydropyrane (4 → 24). Particular attention is given to rationalization of the mechanisms underlying these additions and the regio‐ and diastereoselectivities attainable.
Epoxytetrahydroedulan, a New Terpenoid from the Hairpencils of Euploea (Lep.: Danainae) Butterflies
Authors: Francke Wittko , Schulz Stefan , Sinnwell Volker , König Wilfried A. , Roisin Yves
Published: July 2007

The main component among the volatiles from hairpencils of male danaid butterflies of the genus Euploea was found to be 9,10‐epoxytetrahydroedulan: (1R,2S,4S,7R, 10S)‐1,6,6,10‐tetramethyl‐3,11‐dioxatricyclo[5.4.0.02,4]undecane (12). Identification and synthesis of the compound are described. Another edulan derivative, (1R,3S,6R)‐1,3,7,7‐tetramethyl‐2‐oxabicyclo[4.4.0]dec‐9‐en‐8‐one (13) could be identified from the hairpencils of Danaus plexippus males.
Synthese von 1,4‐Di‐O‐acetyl‐2,3‐didesoxy‐α/β‐D‐pentofuranose und ‐pentopyranose
Authors: Diekmann Elke , Friedrich Klaus , Lehmann Jochen
Published: July 2007

Synthesis of 1,4‐Di‐O‐acetyl‐2,3‐dideoxy‐α/β‐D‐pentofuranose and ‐pentopyranose

Starting from D‐mannitol, the diacetates 8 and 9 of 2,3‐dideoxy‐D‐pentofuranose and ‐pentopyranose are synthesized. The 1H‐NMR and 13C‐NMR spectra of the compounds are given.
Condensed Purines, I Synthesis of 6,7‐Dihydro‐1,3‐dimethylpyrimido[2,1‐f]purine‐2,4,8(1H,3H,9H)‐triones
Authors: Kalcheva Veneta , Stoyanova Diana , Simova Svetlana
Published: July 2007

The title compounds 2a–d and 4a–d are the sole products of the reaction between 8‐aminotheophylline (1) or 8‐(benzylamino)theophylline (3) and methyl acrylate, crotonate, methacrylate, and cinnamate in the presence of basic catalysts (Triton B or KOH). The structures of the compounds were determined by elemental analysis, spectral data, chemical transformations, and synthesis.
Studies with Alkylheteroaromatic π‐Deficient Compounds: Novel Synthesis of Thieno[3,4‐d]pyridazines and Phthalazines
Authors: Elnagdi Mohamed Hilmy , Negm Abdalla Mohamed , Erian Ayman Wahba
Published: July 2007

Ethyl 1‐aryl‐5‐cyano‐1,6‐dihydro‐4‐methyl‐6‐oxo‐3‐pyridazinecarboxylates 1 react with elemental sulphur in ethanolic basic solutions to yield thieno[3.4‐d]pyridazines 2. Compounds 2 readily react with electron‐deficient olefins to yield phthalazines.
Synthetic microbial chemistry, XXIII. Synthesis of optically active virginiae butanolides A, B, C, and D and other autoregulators from streptomycetes
Authors: Mori Kenji , Chiba Naoki
Published: July 2007

Optically active A‐factor (1), the factor from Streptomyces viridochromogenes (2), the factors from S. bikiniensis and S. cyaneofuscatus (3–5), and virginiae butanolides A (6), B (7), C (8), and D (9) were synthesized starting from (S)‐(−)‐paraconic acid (10). The absolute configurations of virginiae butanolides A and C were deduced to be (2S,3R,1′R).
Constituents of holothuroidea, I. Isolation and structures of three triterpenoid aglycones, cucumechinol A, B, and C, from the sea cucumber Cucumaria echinata
Authors: Miyamoto Tomofumi , Togawa Kenichi , Higuchi Ryuichi , Komori Tetsuya
Published: July 2007

Three new holostane2)‐type triterpenoid aglycones named cucumechinol A (1), B (2), and C (3) were isolated from the acidic hydrolysate of the crude glycoside mixture prepared from the whole sea cucumber Cucumaria echinata. The structures were identified on the basis of spectral evidence as 3β‐hydroxyholost‐9(11)‐ene‐16,23‐dione (1), 3β‐hydroxyholost‐9(11)‐en‐23‐one (2), and 3β‐hydroxyholost‐8(9)‐ene‐16,23‐dione (3), respectively.
Biologically active glycosides from asteroidea, XX. Glycosphingolipids from the starfish Asterina pectinifera,1. Isolation and characterization of acanthacerebroside B and structure elucidation of related, nearly homogeneous cerebrosides
Authors: Higuchi Ryuichi , Natori Takenori , Komori Tetsuya
Published: July 2007

A ceramide monohexoside, acanthacerebroside B1b,2a), was purified from the water‐insoluble lipid fraction of the chloroform/methanol extract of the starfish Asterina pectinifera Müller et Troschel using reversed‐phase HPLC. A new method for identification of components of the ceramide by means of HPLC was developed. The separation and structure elucidation of related, nearly homogeneous cerebrosides which behaved as homogeneous compounds is also described.
Biologically active glycosides from asteroidea, XXI. Structure of pectinioside C: Determination of the stereochemistry of the C‐17 side chain of the steroidal aglycone
Authors: Honda Masanori , Igarashi Takashi , Komori Tetsuya
Published: July 2007

The 3,6‐di‐O‐acetyl derivative 3 of the desulfated aglycone of pectinioside C, (20S,24S)‐24‐ethylthoransterol A (2), and its 24R and 24RS stereoisomers 4 and 27 have been synthesized stereoselectively from the pregnane derivative 3,6‐di‐O‐acetyl‐asterone (5). Herewith, the stereochemistry at the C‐17 side chain of 2 and of pectinioside C (1) has been determined. (20S,24S)‐3β‐Acetoxy‐24‐ethyl‐20‐hydroxycholest‐5‐en‐23‐one (18), its 24R and 24RS stereoisomers 21 and 24, respectively, and some steroids with (20S)‐20‐hydroxy‐24ζ‐methyl‐26‐homo‐25ζ‐cholestane side chain have also been synthesized.
Desmethyl(trifluormethyl)actinomycine
Authors: Giencke Astrid , Lackner Helmut
Published: July 2007

Demethyl(trifluoromethyl)actinomycins

The synthesis of new 4‐(trifluoromethyl)benzoic acid derivatives 2–10 and their coupling with amino acids and peptides 12, 13, 15 is described. They serve as precursors for the synthesis of the hitherto unknown demethyl(trifluoromethyl)actinocin dimethyl esters 11, demethyl‐trifluoromethyl‐actino‐cinyl peptides 14, 16, 18 and the demethyl‐trifluoromethyl‐actinomycins 17. Although spacially comparable with the methyl residues, the 4‐ and 6‐trifluoromethyl groups have unexpected strong influences on the antibiotic and cytostatic properties of the actinomycins. The CH3/CF3 exchange makes it possible to bring NMR‐analytically useful hetero nuclei into the centre of the actinomycin/DNA complex (Figure 1).
Semisynthetische Myxovirescine: Austausch des α‐Hydroxycarbonsäure‐Segments und Modifikation der Ringgröße
Authors: Borgschulte Katrin , Trowitzsch‐Kienast Wolfram , Höfle Gerhard
Published: July 2007

Semisynthetic Myxovirescins: Exchange of the α‐Hydroxycarboxylic Acid Segment and Modification of the Ring Size

Partial degradation reactions of the macrocyclic lactam‐lacton antibiotic myxovirescin A1 (1) yield the key building blocks 2 and 26. From these myxovirescin analoga are reconstituted with various alkyl groups at position C‐2 with R and S configuration. Furthermore a ring‐contracted (24) and a ring‐enlarged (29) macrocycle are synthesized. The growth of E. coli is best inhibited by the natural myxovirescin A1 with a (2S) propyl substitution whilst 24 and 29 do not inhibit the growth of E. coli at all.
Hydrazinüberbrückte Annulene, 7. Synthese von 6H‐9b,9c‐Diazacyclopenta[cd]phenalen‐5,7‐dicarbonsäure‐diethylester
Authors: Flitsch Wilhelm , Lewinski Ulrike , Temme Robert , Wibbeling Birgit
Published: July 2007

Hydrazino‐Bridged Annulenes, 7. — Synthesis of Diethyl 6H‐9b,9c‐Diazacyclopenta[cd]phenalene‐5,7‐dicarboxylate

The 1,4‐dihydropyridine 4 has been obtained from 1‐amino‐pyrrole and diethyl 2,6‐dioxo‐3,5‐heptanedicarboxylate. Subsequent Vilsmeier reaction led to the aldehyde 7 which could be transformed into the tricyclic aldehyde 8b in a repeated Vilsmeier reaction. Final cyclization was achieved with sodium ethanolate yielding the extremly unstable diazacyclo‐penta[cd]phenalene derivative 9.
Pyrrolo[1,2‐b]cinnolin‐6,8‐dicarbonsäure‐diethylester: Produkt einer anomalen Vilsmeier‐Reaktion
Authors: Flitsch Wilhelm , Lauterwein Jürgen , Leimkühler Manfred , Leaver Derek , Lewinski Ulrike , Mattes Rainer , Temme Robert , Wibbeling Birgit
Published: July 2007

Diethyl Pyrrolo[1,2‐b]cinnoline‐6,8‐dicarboxylate, a Product of an Anomalous Vilsmeier Reaction

A byproduct of the Vilsmeier reaction of 1 has been shown by X‐ray structure determination to be the pyrrolo[1,2‐b]cinnoline 3. Informations concerning the mechanism of formation of 3 have been obtained from labeling experiments and an unequivocal assignment of NMR spectra.
Synthesis of N,N′‐bis(phenylsulfonyl)‐1,2‐bis(4‐pyridyl)ethylenediamines
Authors: Braña Miguel F. , Castellano José M. , Yunta María J. R.
Published: July 2007

Reaction of (4‐pyridylmethyl)amine (3) with benzenesulfonyl chlorides 2a—i affords the corresponding N‐(4‐pyridylmethyl)benzenesulfonamides 4a—i which are converted into the N‐oxides 5 by treatment with hydrogen peroxide and acetic acid. Treatment of compounds 4 with their N‐oxides 5 in acetic anhydride results in dimerization to give the corresponding N,N′‐bis(phenylsulfonyl)‐1,2‐bis(4‐pyridyl)ethylenediamines 6a–d, f. The mixed ethylenediamines 6e, g are similarly synthesized from differently substituted sulfonamides and N‐oxides.
Reactions of 1‐acetyl‐3‐(dicyanomethylene)‐1,3‐dihydro‐2H‐indol‐2‐one with amines
Authors: Younes Mansour I.
Published: July 2007

Reaction of the title compound 1 with aliphatic, aromatic or heterocyclic amines leads to quinoline and indole derivatives 3 and 4, respectively.
Synthese enantiomerenreiner γ‐Keto‐δ‐aminosäuren, zentrale Bausteine vieler Enzyminhibitoren
Authors: Radunz Hans‐Eckart , Reißig Hans‐Ulrich , Schneider Günther , Riethmüller Angelika
Published: July 2007

Synthesis of Enantiomerically Pure γ‐Keto‐δ‐amino Acids, Central Building Blocks of Enzyme Inhibitors

An enantioselective and efficient synthesis of γ‐keto‐δ‐amino acids as building blocks for certain enzyme inhibitors is presented. These compounds are also attractive for syntheses of homostatine derivatives.
Diels‐Alder reactions of 1‐phenylpyrano[3,4‐b]indol‐3‐ones with alkynes: New functionalized carbazoles
Authors: Pindur Ulf , Erfanian‐Abdoust Houshang
Published: July 2007

3‐Indolylalkanoic acids 2 react with benzoic acid anhydride under catalysis of Et2O ‐ ZnCl2 and mild conditions to furnish the 1‐phenyl‐substituted pyrano[3,4‐b]indol‐3‐ones 1c, 1d, and 3a, 3b. Products 1c, 1d, and 3b may be converted into the novel functionalized carbazoles 4 and 5 by reaction with acceptor‐substituted alkynes.
Synthese neuer 8‐Azapurine
Authors: Ried Walter , Guryn Roman , Laoutidis Joannis
Published: July 2007

Synthesis of New 8‐Azapurines

The ethyl 5‐amino‐1H‐1,2,3‐triazole‐4‐carboxylates 1 react with orthoformate and hydrazine or substituted phenethylamine to yield the 8‐azapurines 3, 5, and 8, respectively.
Pheromone, 76. Synthese der Enantiomeren von 10‐Methyldodecylacetat und 12‐Methyltetradecylacetat, chiralen Pheromonkomponenten von Adoxophyes‐Arten (Lepidoptera: Tortricidae)
Authors: Bestmann Hans Jürgen , Frighetto Rosa T. S. , Frighetto Nelson , Vostrowsky Otto
Published: July 2007

Pheromones, 76. Synthesis of the Enantiomers of 10‐Methyldodecyl Acetate and 12‐Methyltetradecyl Acetate, Chiral Pheromone Components of Adoxophyes Species (Lepidoptera: Tortricidae)

From enantiomeric (R)‐(−)‐ and (S)‐(+)‐2‐methylbutyl bromide (3), available by resolution of (R)‐(−)‐phenylglycinol amides of rac‐2‐methylbutanoic acid, and from enantiomeric 6‐methyloctyl bromide (7) the corresponding phosphonium salts were obtained. Wittig olefination yielded the optically active methyl‐branched olefinic THP ethers 12 and 13, hydrolysis, catalytic hydrogenation, and acetylation gave rise to the formation of the chiral title compounds (R)‐(−)‐ and (S)‐(+)‐10‐methyldodecyl acetate (1) and (R)‐(−)‐ and (S)‐(+)‐12‐methyltetradecyl acetate (2).
The synthetic utility and mechanisms of the hydrogen iodide isomerization and the oxo reaction in the modification of chlorophyll derivatives
Authors: Hynninen Paavo H.
Published: July 2007

Hydrogen iodide in glacial acetic acid has served as a versatile reagent in modifications of chlorophyll and its closely related derivatives, e.g. pheophorbides and 3‐vinylchlorins, to 3‐ethyl‐porphyrins (HI isomerization) or to 31‐oxoporphyrins (oxo reaction). Nevertheless, the mechamisms of these important reactions have remained obscure. In this paper, the reaction conditions used by H. Fischer for the HI isomerization and the oxo reaction are first thoroughly examined. Secondly, a carbocation rearrangement mechanism is suggested for the HI isomerization. Thirdly, the oxo reaction is rationalized by means of a reaction between a chlorin 31‐carbocation and water nucleophile and subsequent dehydrogenation by triplet oxygen. Finally, some related unsolved problems of chlorophyll chemistry are briefly discussed.
4,5‐dihydroisoxazoles, IX. Reactions of 3‐aryl‐4,5‐dihydro‐4‐methylene‐5‐morpholinoisoxazoles with 2,4‐diaryl‐5(4H)‐oxazolones: A new synthesis of tetrahydro‐6‐oxo‐3‐pyridinecarbaldehydes
Authors: Erba Emanuela , Pocar Donato
Published: July 2007

The 5(4H)‐oxazolones 1a–e react with 5‐morpholinoisoxazoles 2a–b to afford the 4‐[(4‐isoxazolyl)methyl]‐5(4H)‐oxazolones 3a–g. Compounds 3 are hydrogenated with Pd/C in dioxane to yield the corresponding 1,4,5,6‐tetrahydro‐6‐oxo‐3‐pyridinecarbaldehydes 6a–d.
Stereoselektive Totalsynthese von rac‐Yohimb‐15‐enon
Authors: Rosenmund Peter , Brandt Bernhard , Flecker Peter , Hoffmann Eberhard
Published: July 2007

Stereoselective Synthesis of rac‐Yohimb‐15‐enone

The Robinson annulation of an octahydroindolo[2,3‐α]quinolizin‐2‐one is a general concept for the synthesis of yohimbine alkaloids. Using the phenylsulfonyl group for activation, a diastereoselective synthesis of rac‐yohimben‐17‐one 21 has been developed. A new synthesis of aromatic amines 23 and 24 has been discovered.
Synthesen von Galactose‐Cluster‐haltigen Steroid‐Derivaten
Authors: Peter Martin G. , Boldt Peter C. , Niederstein Yvonne , Peter‐Katalinić Jasna
Published: July 2007

Synthesis of Galactose‐Cluster‐Containing Steroid Derivatives

The synthesis of galactose clusters that are linked to a steroid moiety by a peptide‐like spacer unit is described. The galactose cluster is obtained by Koenigs‐Knorr glycosylation of TRIS‐Gly‐Fmoc (2b) under Helferich conditions. Peptide and ester bonds are formed after activation of carboxylic acids as diphenylthiophene dioxide (TDO) esters. 6a is synthesized in a convergent way by coupling of (Ac4Gal)3‐TRIS‐Gly (3e) with cholesteryl TDO succinate (5b). Coupling of (Ac4Gal)3‐TRIS‐Gly hydrogen succinate (3f) with Gly‐O‐Chol (5d) by means of EEDQ yields 6d. Reaction of (Ac4Gal)3‐TRIS‐Gly‐SUCC‐O‐TDO (3g) with 25‐hydroxycholesterol leads in a linear sequence to the oxysterol derivative 6f. Selective cleavage of the acetyl groups from galactose units yields the known compound 6b and the new derivatives 6e and 6g.
The synthesis and analysis of the conformation in solution of the dolastatin 3 diastereomer cyclo[‐L‐Pro‐L‐Leu‐D‐(Gln)Thz‐(Gly)Thz‐L‐Val‐]
Authors: Bredenkamp Martin W. , Holzapfel Cedric W. , van Zyl Wynand J.
Published: July 2007

The cyclic peptide cyclo[‐L‐Pro‐L‐Leu‐D‐(Gln)Thz‐(Gly)Thz‐L‐Val‐] (1a), which is a diastereomer of the antineoplastic agent dolastatin 3 (1b), and contains the unusual thiazole amino acids, was synthesized. All the peptide bonds of the cyclic peptide 1a are trans in solution, and the compound is conformationally homogeneous, as deduced by CD spectroscopy and comprehensive NMR spectroscopy. The conformation was refined by SYBYL molecular force‐field calculations. The saddle‐like conformation contains three intramolecular, but no transannular hydrogen bonds.
Heterocyclische Siebenring‐Verbindungen, XXXVI. Synthese und Eigenschaften des 1,4‐Benzoxazepins und einiger monosubstituierter Derivate
Authors: Hofmann Hans , Fischer Herbert
Published: July 2007

Heterocyclic Seven‐Membered Ring Compounds, XXXVI. — Synthesis and Properties of 1,4‐Benzoxazepine and of Some Monosubstituted Derivatives

O‐Alkylation of salicylamide with bromoacetaldehyde diethyl acetal and subsequent thermal ring closure yields the lactam 2, which is converted into the imide chloride 3. Pd(0)‐catalyzed dehalogenation of compound 3 with tributyltin hydride leads to the desired 1,4‐benzoxazepine (4), a thermally very unstable compound which prefers polymerization to valence isomerization. O‐Alkylation of the lactam 2 and S‐alkylation of the thiolactam 8 yield the 5‐substituted 1,4‐benzoxazepines 6 and 9, resp., which are thermally considerably more stable than the parent compound 4. Thus, they are capable of the expected thermal isomerization to the corresponding hydroxyisoquinolines 10 and 11, resp. The photoisomerization of the 1,4‐benzoxazepines 4, 6, and 9 leads to the thermally very unstable dihydroazetes 12, 13, and 14, of which only the methylthio compound 14 could be isolated as crystalline compound.
Orthoamide, XLVI. Beiträge zur Chemie von Bis(dialkylamino)malononitrilen
Authors: Kantlehner Willi , Greiner Ulrich
Published: July 2007

Ortho Amides, XLVI. — Contributions to the Chemistry of Bis(dialkylamino)malononitriles

The reaction of chloroformamidinium chlorides 2 with sodium cyanide in the two‐phase system ether/water affords bis(di‐alkylamino)malononitriles 3 with good yields. From 3a and morpholine or aniline the guanidines 5 and 6 can be obtained, respectively. Alcohol‐free sodium ethoxide transforms 3a into the urea acetal 10b, whereas in the reaction of 3a with alkoxides in alcohol ortho carbamic esters 11a, b are produced. The malonic esters and acetoacetic esters 12 react with 3a in the presence of two equivalents of sodium hydride to give the ketene aminals 13. The reactions of 3a with malononitrile furnishes the guanidinium salt 14, which is cyclized by hydrogen chloride to the pyridinetricarbonitrile 15. In the presence of sodium hydride, 3a and malononitrile or cyanoacetic esters 17 form the ketene aminal 16 and the 1,2,3‐tricyanopropenides 18a–c, respectively. The analogous salts 20 and 21 result from the reaction of 3a with the barbituric acid derivatives 19a, and b, respectively. Hydrogen chloride reacts in ether with 3a to afford the piperazinetetracarbonitrile 22. Reaction of carboxylic acid chloride yields the cyanoformamidinium salt 28a; byproducts are acyl cyanides 29 and dimeric acyl cyanides 30. Triethyloxonium tetrafluoroborate transforms 3a into the salt 28b. Bromine and iodine react with 3a to produce the salts 28c, d and 28e, f, respectively, depending on the stoichiometric ratios of the starting materials. The thiocyanate 28g is prepared from sulfur and 3a.
Heterocyclische β‐Enaminoester, 53. Neue 5,8‐Dihydropyrido‐ und 4H‐Pyrano[2,3‐d]pyrimidine
Authors: Wamhoff Heinrich , Paasch Joachim
Published: July 2007

Heterocyclic β‐Enamino Esters, 53. — Novel 5,8‐Dihydropyrido‐ and 5H‐Pyrano[2,3‐d]pyrimidines

The 1,4‐dihydropyridine enamino esters 1a and 4 react with phenyl isocyanate to afford the ureas 2 and 5, resp., which are cyclized to yield the 5,8‐dihydropyrido[2,3‐d]pyrimidines 3 and 6, resp., while the 1,4‐dihydropyridine bisenamino ester 7a gives accordingly, via bisurea 8, the pyrido[2,3‐d:6,5‐d′]dipyrimidine 10. The 2‐amino‐4H‐pyran‐3‐carboxylate 11 is smoothly phosphorylated to form 12. Treatment of 12 with phenyl isocyanate results in a ring closure to the 4H‐pyrano[2,3‐d]pyrimidine 14. Similarly and according to this principle, the 5,8‐dihydropyrido[2,3‐d]pyrimidine 16 is smoothly formed upon treatment of the iminophosphorane 15 with phenyl isocyanate, while the 2,6‐diamino‐1,4‐dihydropyridine 7b after phosphorylation affords the mono‐iminophosphorane 17, which undergoes cyclization with isocyanate to the 5,8‐dihydropyrido[2,3‐d]pyrimidine 18. With isopropylsulfamoyl chloride 1b and 7a form the mono‐ and bissulfamides 20 and 21, resp., which could not be cyclized further.
Amphiphilic carbohydrate‐based mesogens, VI. Synthesis of a series of alkyl 1‐thio‐D‐glucopyranosides and their regioselective reductions to 1‐alkylthio‐1‐deoxy‐D‐glucitols
Authors: Dahlhoff Wilhelm V.
Published: July 2007

Alkyl 1‐thio‐α,β‐D‐glucopyranosides (hexyl to decyl, 1a–e) are prepared by reaction of penta‐O‐acetyl‐β‐D‐glucopyranose with the respective thiols in the presence of diethyl ether — trifluoroborane, followed by deacetylation. 1a–e are converted into their tetra‐O‐diethylboryl derivatives 2a–e and reduced with ethyldiboranes(6) in the presence of the catalyst 9‐methylsulfonyloxy‐9‐borabicyclo[3.3.1]nonane (9‐BBN‐mesylate, MSBBN) to give the mesogenic 1‐alkylthio‐1‐deoxy‐D‐glucitols 3a–e after deboronation.