bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ein Porphyrinogen mit 1,8‐Diphenylanthracen‐Brücke
Authors: Marx Thomas , Breitmaier Eberhard 
Published: July 2007

A Porphyrinogen with 1,8‐Diphenylanthracene BridgeThe title compound 3 was prepared in good yield by cyclization of 1,8‐Bis(4‐formylphenyl)anthracene (2) with the 2,2′ – Dipyrrylmethane 1.
Photochemical Reactions of Caffeine with Aliphatic Aldehydes
Authors: Erndt Aleksander , Fiedorowicz Maciej , Kostuch Andrzej , Para Andrzej 
Published: July 2007

AbstractPhotochemical reactions of caffeine with several aliphatic aldehydes are performed. In the reactions with ethanal, propanal and butanal stable 8‐acyl‐8,9‐dihydrocaffeines 2 and 3 together with unreduced 8‐acylcaffeines 4 and 8‐(α‐hydroxyalkyl)caffeines 6 are produced. Under similar conditions, the reactions of 2‐methylpropanal, 2‐methylbutanal and 2,2‐dimethylbutanal resulted in the formation of the corresponding 8‐alkylcaffeines 7.
Vier neue Pregnanglycoside aus Gongronema latifolium (Asclepiadaceae)
Authors: Schneider Christiane , Rotscheidt Klaus , Breitmaier Eberhard 
Published: July 2007

Four New Pregnane Glycosides from Gongronema latifolium (Asclepiadaceae)Four so far unknown pregnane biosides have been isolated from the chloroform extract of the leaves of Gongronema latifolium Benth. et Hook. (Asclepiadaceae). From one‐ and twodimensional NMR experiments (NOE difference spectroscopy, ROESY, H,H‐COSY, C,H‐COSY, HMBC) their structures have been established as 3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1a), 3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐oleandropyranosyl]‐17β‐marsdenin (1b), 12‐O‐acetyl‐3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1c) and 11‐O‐acetyl‐3‐O‐[6‐deoxy‐3‐O‐methyl‐β‐D‐allopyranosyl‐(1→4)‐β‐D‐canaropyranosyl]‐17β‐marsdenin (1d).
Novel Porphyrinoids, 13. – Synthesis and Electrophilic Substitution of New Partially β‐Unsubstituted [18]Porphyrins
Authors: Franck Burchard , Krautstrunk Gerhard 
Published: July 2007

AbstractThree porphyrins2, 3, and4, related to Hans Fischer's octaethylporphyrin1, but with unsubstituted pyrrole β‐positions were synthesized via the biladiene pathway. The ring‐closing reaction to form the porphyrin reveals a conformational control, calledhelical effect. These new porphyrins made possible an investigation of the regioselectivity of electrophilic aromatic substitutions at the porphyrin perimeter.
Novel Porphyrinoids, 14. – Biomimetic Syntheses of Doubly N,N′‐Bridged [18]Porphyrinogens
Authors: Franck Burchard , Timmermann Ralf , Sirges Wolfram 
Published: July 2007

AbstractSix N,N′‐alkylene‐bridged bispyrroles 9a–9e and one N,N′‐oxaalkylene‐bridged bispyrrole 16 with a reactive group at C‐1 of each pyrrole unit were synthesized in 53–78% yields. Acid‐catalyzed “biomimetic” condensations of the bispyrroles with N,N′‐C3 to N,N′‐C5 bridges yielded N,N′:N″,N‴doubly bridged porphyrinogens 14, 15, 17, 18, which are novel heterocyclic systems. By exchanging one CH2 group for oxygen in the N,N′‐alkylene chain of 9e to reduce the Prelog strain, the condensation yield was significantly increased. The N,N′‐C1‐and the N,N′‐C2‐bridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in one case cyclized to give a N,N′‐C1‐bridged dipyrrylmethane 12 instead.
Dithio‐ und Thionester, 59. Zur Reaktion von aliphatischen Dithiosäure‐dianionen mit Schwefelkohlenstoff
Authors: Hartke Klaus , Rettberg Norbert , Dutta Dinah , Gerber Hans‐Dieter 
Published: July 2007

Dithio and Thiono Esters, 59. – Reactions of Aliphatic Dithio Acid Dianions with Carbon DisulfideDianions 2 of dithioacids 1 and carbon disulfide yield in a kinetically controlled reaction at – 78°C S‐adducts (e.g. 3, 13) or in a thermodynamically controlled reaction at room temperatur C‐adducts [the tetrahthiomalonic acid trianions 10 or the 2,2‐dimethyltetrathiomalonic acid dianion 15]. Acidification of 10 and subsequent reactions give rise to the tetrathiomalonic acids 18 and its derivatives 19 with 2,6,9,10‐tetrathiaadamantane structure. Deprotonation of 10a leads to the tetrathiomalonic acid tetraanion (20) which may be alkylated to yield the tetrakis(alkylthio)allenes 21. By condensation of the dithioacid dianions 2, the tetrathiomalonic acid trianions 10 and the tetrathiomalonic acid tetraanion (20) with 2,3‐dichloro‐1,4‐naphthoquinone (32) a number of naphtho[2,3‐d]‐1,3‐dithiole‐4,9‐diones [e.g. 33, 35, 37] are obtained.
Enzymes in Organic Synthesis, 15. – Synthesis of Methyl (S)‐(−)‐2,3‐O‐Isopropylideneglycerate by Enantioselective Enzyme‐catalyzed Hydrolysis of Methyl (±)‐2,3‐O‐Isopropylideneglycerate
Authors: Schick Hans , Schrötter Eberhard , Szymanowski Matthias , Knoll Alexander 
Published: July 2007

AbstractIn contrast to porcine pancreatic lipase (PPL), the serine proteases aP 41 and thermitase are suited as catalysts for the enantioselective ester hydrolysis of methyl (π)‐2,3‐O‐isopropyl‐ideneglycerate (rac‐1). These enzymes allow the preparation of methyl (S)‐(−)‐2,3‐O‐isopropylideneglycerate (1) with an enantiomeric excess of 84–87% in a yield of 19–27% related to the starting racemate.
Reductive Transformations of 6H‐1,2‐Oxazines with Hydride Reagents: Formation of Aziridines and 3‐Hydroxyalkylated 1,2‐oxazines
Authors: Zimmer Reinhold , Homann Kai , Reißig Hans‐Ulrich 
Published: July 2007

Abstract6H‐1,2‐Oxazines 1 and 3 are converted into aziridines 2 and 4, respectively, by reduction with LiAlH4. Reduction of 1,2‐oxazine 5 lacking the 6‐alkoxy substituent leads to phenyl ketone 6, 6‐Alkoxy‐substituted 1,2‐oxazine‐3‐carboxylates 7, 9, and 11 are reduced with NaBH4 to give the corresponding 3‐hydroxymethylated compounds 8, 10, and 12 in good yields.
Total Synthesis of Thymosin β4 by Fragment Condensation
Authors: Kapurniotu Afroditi , Link Peter , Voelter W. 
Published: July 2007

AbstractThe total synthesis of thymosin β4 by means of classical methods using three protected fragments is described. For their syntheses the Z/tBu strategy and temporary phenyl ester protection of the C‐terminal carboxyl were used. Various coupling procedures were applied in order to optimize the yields of the synthesis. The BOP/HOBt method proved to be very efficient for the coupling of larger fragments. The fragment condensation for the synthesis of protected thymosin β4 was performed by two different strategies. The deprotected thymosin β4 was purified by prep. HPLC on a RP‐18 column. Applying the first synthetic strategy the 43‐peptide was obtained in 12% overall yield for the final steps of the synthesis, including two fragment condensations, two hydrogenations, deprotection, and purification. The second synthetic strategy afforded thymosin β4 in 4% overall yield (based on the final synthetic steps: two fragment condensations, two hydrogenations, deprotection, and purification). The purified products of both synthetic pathways were shown to be identical with the natural thymosin β4, isolated from calf thymus tissue, according to HPLC, capillary zone electrophoresis, SDS‐PAGE, ion‐spray mass spectrometry, and amino acid analysis.
1,3‐Dipolar Cycloaddition of Benzonitrile Oxide to Substituted 4,5‐Dihydro‐3‐methylene‐2(3H)‐furanones
Authors: Štverková Slávka , Žák Zdirad , Jonas Jaroslav 
Published: July 2007

AbstractBenzonitrile oxide cycloadds to the CC bond of substituted 4,5‐dihydro‐3‐methylene‐2(3H)‐furanones 1a–1g. Thus, (E)‐1a and (E)‐1b are converted into the corresponding isoxazolinespirodihydrofuranones (4RS,5RS)‐2a and (4RS,5RS)‐2b, and (E)‐1c is converted into a mixture of isomers (4RS,5RS)‐2c and (4RS,5RS)‐3c. The reactions of (E)‐1d–1g yield mixtures of the corresponding diastereomeric isoxazolinespirodihydrofuranones (4RS,5RS,8RS)‐2d and (4RS,5RS,8SR)‐2d, (4RS,5RS)‐3e and (4RS,5SR)‐3e, (4RS,5RS)‐3f and (4RS,5SR)‐3f, (4RS,5RS)‐3g and (4RS,5SR)‐3g. The addition of benzonitrile oxide to (Z)‐1a gives (4RS,5SR)‐2a and 4a. In the cycloaddition with (E)‐1a the p‐tolylsulfonyloxy group in the intermediate (4RS,5RS)‐2a is partially replaced by chlorine to give (4RS,5RS)‐2h. – The structures of (4RS,5RS)‐2h, (4RS,5RS)‐3e, (4RS,5SR)‐3e, and 4a are determined by X‐ray analysis. The 1H‐ and 13C‐NMR spectra of the products are discussed and the reaction course is rationalized on the basis of HOMO‐LUMO energy gaps.
Glycosyl Imidates, 63. – Synthesis of the Sulfated Steroidal Glycosides Forbeside E3 and E1
Authors: Jiang Zi‐Hua , Han Xiao‐Bing , Schmidt Richard R. 
Published: July 2007

AbstractReaction of 6α‐hydroxy‐substituted steroids 7 and 8 with the 2‐O‐benzyl‐protected quinovosyl donors 4a, b afforded α,β‐mixtures of the glycosides 9a, b; with O‐acetyl‐protected donor 4c, due to neighboring group participation, exclusively β‐glycoside 9cβ was obtained. Similarly, reaction of donor 4c with 3β‐O‐silyl‐protected 6α‐hydroxy‐steroid 12 furnished β‐connected 6O‐quinovosyl derivative 14 in high yield. 3‐O‐Desilylation of 14 with TBAF and ensuing 3‐O‐sulfation with pyridine/sulfur trioxide complex yielded pyridinium sulfate derivative 17, which turned out to be rather unstable. Treatment of 17 with sodium methoxide in methanol gave in high yield forbeside E 3 (1) the physical data of which were in good agreement with literature reports. Diastereoselective reduction of the keto group in 18 with NaBH4 led preferentially to 19 which was deacetylated to afford forbeside E 1 (2).
Basenhydrierte Phosphonsäure‐Derivate von Pyrimidinnucleosiden, Nebenprodukte bei der Desoxygenierung von 2′‐O‐Phenoxythiocarbonyl‐Vorstufen
Authors: Morr Michael , Ernst Ludger 
Published: July 2007

Base‐Hydrogenated Phosphonic Acid Derivatives of Pyrimidine Nucleosides, Side Products in the Deoxygenation of 2′‐O‐Phenoxythiocarbonyl PrecursorsPersilylation of N4‐anisoyl‐1‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphorylmethyl‐2‐O‐phenoxythiocarbonyl‐β‐D‐ribofuranosyl)cytosine (1) with iodotrimethylsilane followed by a Barton‐McCombie reaction with Bu3SnH/azobis(isobutyronitrile) and hydrolysis with Et3NH+ buffer furnishes, in a side reaction, the N4‐anisoyl‐O5′‐benzoyl‐3′‐deoxy‐3′‐phosphonomethyl‐3,4,5,6‐tetrahydro‐cytosine lactones 4a and 4b, which are epimers at C‐4 and can be separated by chromatography. Two‐step hydrolysis of 4a and/or 4b yields an epimeric mixture of 1‐(3‐deoxy‐3‐phosphonomethyl‐β‐D‐ribofuranosyl)‐3,4,5,6‐tetrahydro‐uracil (6a/6b). A possible mechanism of the formation of 4a/4b from 1 via persilylated 2,2′‐anhydro‐N4‐anisoyl‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphoryl‐β‐D‐arabinofuranosyl)cytosine (9) as well as the reactivity of 9 and the behaviour of methyl 5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphoryl‐2‐O‐phenoxythiocarbonyl‐β‐D‐erythro‐pentofuranoside (17) under the same reaction conditions are discussed. The structures of all new compounds are confirmed by their 1H‐, 13C‐, 31P‐NMR and FAB mass spectra.
Synthesis and Reductive Elimination Reactions of Aryl Thioglycosides
Authors: Fürstner Alois 
Published: July 2007

AbstractTreatment of the sugar hemiacetals 1, 5, 7, 10, 12 and 14 with ArSSAr (Ar = phenyl, 2‐pyridyl, 2‐benzothiazolyl) and trialkylphosphanes affords in an SN2 process the corresponding aryl thioglycosides 3, 6, 8, 9, 11, 13, 15 and 16 in good to excellent yields. The reaction can be performed in a variety of solvents of greatly different polarity and avoids the use of free thiols and Lewis acid catalysts. The promoting phosphane has to carry at least two alkyl groups, with R3P (R = short, unbranched alkyl group) being best suited in terms of yield and reaction rate. In contrast, triphenylphosphane and phosphites are inactive. The reaction is compatible with a variety of functional groups and distinguishes between the anomeric center and other free hydroxyl groups in the substrates. Thus, thioglycosides from partially protected or unprotected sugars can be readily obtained. Treatment of phenyl thioglycosides 13a and 3a with potassium‐graphite laminate (C8K) in THF affords the corresponding pyranoid or furanoid glycals 17 and 18 by reductive elimination.
Conversion of Fatty Acids and Derivatives, IV. Conversion of Fatty Acid Methyl Esters into Dialkylated Succinic Esters by Oxidative Coupling of their Enolates
Authors: Quermann Rolf , Maletz Reinhard , Schäfer Hans J. 
Published: July 2007

AbstractThe enolates of fatty acid methyl esters 1a–g are dimerized in good yields (56 to 73%) by means of oxidative coupling with copper(II) bromide to dialkylated succinic esters 2a–g. The configuration of meso‐2a was established by independent synthesis. On treatment with ozone the unsaturated dimer 2c is converted to the tetracarboxyl compound 6. Epoxidation of 2g leads to the corresponding bisepoxy diester 7.
Antibiotika aus Gleitenden Bakterien, LV – Myxochromid A: Ein hochungesättigtes Lipopeptidlacton aus Myxococcus virescens
Authors: Trowitzsch‐Kienast Wolfram , Gerth Klaus , Wray Victor , Reichenbach Hans , Höfle Gerhard 
Published: July 2007

Antibiotics From Gliding Bacteria, LV. – Myxochromide A: A Highly Unsaturated Lipopetide from Myxococcus virescensThe isolation and structure elucidation of a new family of pigments, the myxochromides, are described. Myxochromide A was determined as a hexapeptide lactone out of: L‐Methyl‐Thr, D‐ or L‐Ala, L‐Leu, L‐Pro, D‐ or L‐Ala and L‐Glu, respectively. Its lactone formation was observed between the γ‐carboxyl of Glu and the OH group of the Me‐Thr residue. The chromophore, a heptaenoic acid, was found to bind as an amide to the N‐atom of the Thr moiety. Myxococcus flavescens produces the same pigments with myxochromide B as the main compounds.
Aromatic and Azaaromatic Diselenides, Benzisoselenazolones and Related Compounds as Immunomodulators Active in Humans: Synthesis and Properties
Authors: Młochowski Jacek , Kloc Krystian , Syper Ludwik , Inglot Anna D. , Piasecki Egbert 
Published: July 2007

AbstractConvenient syntheses of aryl diselenides 2, 1,2‐benzisoselenazol‐3(2H)‐ones 4 and their 1‐oxides 7 are reported. Reductive conversions of these compounds to bis(2‐carbamoyl)‐phenyl diselenides 5 and oxidative cyclization of 5 to 1,2‐benzisoselenazol‐3(2H)‐one 1‐oxides 7 as the methods for the synthesis of these compounds are reported. Their ability to induce cytokines, such as TNF and IFN‐γ, in human peripheral blood leucocyte cultures is described.
Epoxidierung von Kohlenstoff‐Kohlenstoff‐Doppelbindungen in Terpenen durch Linolsäurehydroperoxide
Authors: Meyer Werner , Spiteller Gerhard 
Published: July 2007

Epoxidation of Carbon‐Carbon Double Bonds in Terpenes by Linoleic Acid HydroperoxidesEpoxidation of CC double bonds in terpenes is achieved by reaction with linoleic acid hydroperoxides (LOOH) exemplified with caryophyllene (3), methyl farnesoate (5) and squalene (8). Linoleic acid (9S)‐hydroperoxide was obtained by reaction of linoleic acid (1) with lipoxygenase present in tomato homogenisate. When 18O2‐labeled (9S)‐LOOH (2) was used 18O was found in the terpene epoxide. While 3 is converted under physiological conditions regioselectively in high yiled into its 4,5‐epoxide 4, the yield of epoxidized products from long‐chain molecules, e.g. squalene (8), decreases strongly and no regioselectivity was observed.
Regioselektive Reaktionen an der 17‐Oxogruppe von Androsta‐1,4‐dien‐3,17‐dion nach in‐situ‐Schutz mit Titantetrakis(dimethylamid)
Authors: Müller Andreas , Beckert Rainer , Schönecker Bruno , Weiß Dieter 
Published: July 2007

Regioselective Reactions at the 17‐Oxo Group of Androsta‐1,4‐dine‐3,17‐dione after in situ Protection with Titaniumtetrakis(dimethylamide)After in situ protection of androsta‐1,4‐diene‐3,17‐dione (1) with titaniumtetrakis(dimethylamide) (10) at −20°C to −30°C, the lithium enolates of methyl methoxyacetate (2a) and ethyl acetate (2b) react regio‐ and stereoselectively at the 17‐position to give the 17‐hydroxy‐17α‐pregnanes 12 and 6. Dehydration of 12 and 6 furnishes the 17(20)‐olefins 13 and 14, intermediates for the synthesis of corticoids and gestagens. The reaction of 1 with 10 and 2a at −60°C gives byproducts of a dienone‐benzene rearrangement of the A‐ring. The reactions of 1 with 2a and 2b without titaniumtetrakis‐(dimethylamide) (10) proceed regioselectively at the 3‐position or nonregioselectively at the 3‐ and 17‐positions, respectively.
Aminosäuren, 16. Darstellung von N‐Acyl‐2,3‐didehydro‐2‐aminocarbonsäureestern
Authors: Effenberger Franz , Kühlwein Jürgen , Drauz Karlheinz 
Published: July 2007

Amino Acids, 16. – Synthesis of N‐Acyl‐2,3‐didehydro‐2‐amino Acid Esters[2]N‐Acyl‐2,3‐didehydro‐2‐amino acid esters 3, 5, 7–12, with a great variety of N‐substituents, are obtained in good yields by the perrhenate‐catalyzed decomposition of methyl 2‐azido carboxylates 1 in organic solvents in the presence of the corresponding acyl chlorides 2. By using methyl 2‐azidoisovalerate (1a), the conditions (catalyst, solvent, temperature) for the reaction to give 3a were optimized. The reactivity of acyl chlorides can be strongly enhanced with equimolar amounts of dimethyl formamide, which allows a lowering of the decomposition temperature for this reaction. Under these mild reaction conditions also the unstable N‐acyldehydroalanine derivative 5f can be obtained in good yield.
Etheranaloge der Thio‐ und Dithiophospholipide mit CSP‐Bindung
Authors: Markowska Anna , Młotkowska Barbara , Olejnik Jadwiga , Sażała Małgorzata 
Published: July 2007

Ether Analogues of Thio‐ and Dithiophospholipids with C–S–P BondThe efficient synthesis of 1‐O‐hexadecyl‐2‐O‐methyl‐3‐thioglycero‐3‐phosphocholine (5a) and 1‐S‐hexadecyl‐2‐O‐methyl‐1,3‐dithioglycero‐3‐phosphocholine (5b) based on phosphorylation of 1‐O‐hexadecyl‐2‐O‐methyl‐3‐thioglycerol (3a) and 1‐S‐hexadecyl‐2‐O‐methyl‐1,3‐dithioglycerol (3b) with 2‐chloro‐2‐oxo‐1,3,2‐dioxaphospholane (6) followed by ring opening of the resulting intermediates 4a and 4b is described.
The Synthesis of the Principal Dihydroisocoumarins of Ononis natrix
Authors: Rama Nasim H. , Saeed Aamer , Bird Clive W. 
Published: July 2007

Abstract(±)‐6,8‐Dihydroxy‐3‐undecyl‐3,4‐dihydroisocoumarin (7) and its 6‐O‐methyl and 6,8‐di‐O‐methyl derivatives 6 and 5, isolated as the (−)‐enantiomers from the plant Ononis natrix by other authors, were synthesized starting with (3,5‐dimethoxyphenyl)acetic acid via (±)‐1‐(3,5‐dimethoxyphenyl)tridecan‐2‐yl acetate (2) and its corresponding 2‐formyl and 2‐carboxy derivatives 3 and 4, respectively.
Synthesis of Enantiomerically Pure Tetrahydro‐2‐methylharman
Authors: Shiqi Peng , Min Guo , Winterfeldt Ekkehard 
Published: July 2007

AbstractL‐Tryptophan methyl ester reacts with acetaldehyde in a Pictet‐Spengler condensation to give a 2.5:1 mixture of the stereoisomers (1S,3S)‐2 and (1R,3S)‐2. These were converted by ammonolysis into the corresponding amides (1S,3S)‐3 or (1R,3S)‐3. On methylation of (1S,3S)‐3 or (1R,3S)‐3 the corresponding 2‐methylcarbolineamide (1S,3S)‐4 or (1R,3S)‐4 were obtained. Dehydration of (1S,3S)‐4 or (1R,3S)‐4 affords 2‐methylcarbolinenitrile (1S,3S)‐5 or (1R,3S)‐5. After reduction with NaBH4 (1S,3S)‐5 or (1R,3S)‐5 was decyanated and the title compound (1S)‐6 or (1R)‐6 was obtained. With NOE experiments their stereochemistry were determined and their optical purities were confirmed by measurements using a chiral shift reagent.
Eine einfache, selektive Synthese von (Z)‐tert‐Butylketen‐O,N‐acetalen durch Phenol/Azol‐Austauschreaktion
Authors: Reuther Wolfgang , Ruland Alfred , Gangkofner Stefan , Baus Ulf 
Published: July 2007

A Facile and Selective Synthesis of (Z)‐tert‐Butylketene O,N‐AcetalsMelting the ketene O,O‐acetals 1 with azoles in the presence of a catalytic amount of a proton acid yields the ketene O,N‐acetals 2. The products of this phenol‐azol substitution reaction are obtained as their (E/Z)‐mixtures with the (Z)‐isomers highly predominating. The (E)‐isomers are easily converted into the (Z)‐isomers by a proton acid catalysed isomerisation reaction.
Klassische Synthese eines selektiven Peptid‐Substrates für die Messung der Proteinkinase C
Authors: Spencker Torsten , Goppelt‐Struebe Margarete , Keese Wolfgang , Resch Klaus , Rimpler Manfred 
Published: July 2007

Conventional Synthesis of a Selective Peptide Substrate for Measurements of Protein Kinase CProtein kinase C (PKC), a family of serin/threonin kinases, plays a key role in signal transduction. We have prepared the PKC‐selective peptide substrate H‐Phe‐Lys‐Lys‐Ser‐Phe‐Lys‐Leu‐NH2 (7) by classical solution synthesis. 7 allows PKC‐measurements in crude extracts or permeabilized cells. The protection of the N‐terminal amino acid and the side chains by Boc resp. tert‐butyl groups enables a one‐step liberation of the desired heptapeptide amide 7.
Secondary Metabolites by Chemical Screening, 22. Gabosines, New Carba‐sugars From Streptomyces
Authors: Bach Gabriela , Breiding‐Mack Sabine , Grabley Susanne , Hammann Peter , Hütter Klaus , Thiericke Ralf , Uhr Hermann , Wink Joachim , Zeeck Axel 
Published: July 2007

AbstractChemical screening of different Streptomycetes strains resulted in the detection, isolation, and structure elucidation of a number of novel carba‐sugars. The constitution of these secondary metabolites, named gabosines A to K (1 to 11), was deduced from spectroscopic data as well as chemical transformation reactions. The gabosines exhibit a basic C7 skeleton and can be characterized as hydroxylated branched cyclohexanone derivatives, which show structural similarities to carbohydrates deriving from secondary metabolism. The configuration fo the gabosines (absolute stereochemistry for 1, 4, 5, and 6; relative configuration for the remaining metabolites) was determined by derivatization with chiral acids (Helmchen's method), NMR spectral analysis, as well as by a comparison of optical rotation values with those of the already known gabosines B (2) and C (3). The new term “ketocarbasugars” is used to characterize a typical ketone containing subgroup of carba‐sugars originating from microbial sources. The well available natural gabosines can be used as suitable chiral building blocks.
Chemistry of the Ginkgolides, V. On the Preparation of the Ginkgolide Skeleton
Authors: Weinges Klaus , Rümmler Matthias , Schick Hartmut , Schilling Gerhard 
Published: July 2007

Abstract3,14‐Didehydro‐10‐hydroxyginkgolideOn the nomenclature: The skeleton of the ginkgolides A, B, C, M and J with the natural configuration is called “ginkgolide” since the systematic IUPAC nomenclature is too complicated. According to our nomenclature ginkgolide “A” is 3,10‐dihydroxyginkgolide, ginkgolide “B” is 1,3,10‐trihydroxyginkgolide etc. The numbering of the C atoms (formula 1) and the indexing of the H atoms (formula 2) are those proposed by Nakanishi[2].
(1) was prepared by reaction of 3,10‐dihydroxyginkgolide (3) (ginkgolide “A”) by reaction with phosphoryl chloride in pyridine. Catalytic hydrogenation of 1 leads to 10‐hydroxy‐14‐epiginkgolide (2a), which was epimerized with 4‐(dimethylamino)pyridine (DMAP) in acetonitrile to give 10‐hydroxyginkgolide (3a). 14‐Epiginkgolide (2d) and ginkgolide (3d) were obtained from 2a and 3a via the 10‐O‐phenylthiocarbonyl derivatives 2c and 3c by means of a free‐radical reduction with tri‐n‐butyltin hydride/α,α′‐azobis(isobutyronitrile) (AIBN). By heating the 14‐epiginkgolides 2a and 2b and the ginkgolides 3a and 3b in acetonitrile with DMAP an equilibrium on the side of the ginkgolides was established. The constitution and configuration of the compounds were proven by their 1H‐ and 13C‐NMR spectra.
Synthesis of 6‐Deoxy and 3,6‐Dideoxy Derivatives from Unprotected Glycosides Employing the Mitsunobu Reaction
Authors: Dancy Isabelle , Laupichler Lothar , Rollin Patrick , Thiem Joachim 
Published: July 2007

AbstractStarting with unprotected hexopyranoside derivatives, an efficient synthesis of 6‐deoxy‐ and 3,6‐dideoxyhexopyranosides was achieved in two consecutive steps involving a highly regioselective Mitsunobu reaction and subsequent desulfurization.