bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herstellung von (R,R)‐ oder (S,S)‐2‐Amino‐3‐hydroxycarbonsäuren (allo‐Threonin‐Analoge) durch Acylierung/Reduktion von 2‐t‐Butyl‐3‐methyl‐4‐oxoimidazolidin‐1‐carbonsäure‐t‐butylester (Boc‐BMI)
Authors: Blank Stefan , Seebach Dieter 
Published: July 2007

Preparation of (R,R)‐ or (S,S)‐2‐Amino‐3‐hydroxycarboxylic Acids (allo‐Threonine Analogs) by Acylation/Reduction of t‐Butyl 2‐t‐Butyl‐3‐methyl‐4‐oxoimidazolidine‐1‐carboxylate (Boc‐BMI)While there are numerous methods of preparing threonine analogs by aldol additions of chiral glycine derivatives to aldehydes, only few general routes leading to the epimers with C,C‐bond formation are presently available. This paper describes the acylation of the title compound 1 with acyl chlorides (→ trans products 2–9), the subsequent reduction with LiBHEt3 in THF (→ hydroxyalkylated BMI derivatives 10–14), and acidic hydrolysis to the free allo‐threonines 18–22. The first two steps are totally stereoselective (by NMR analysis), and the overall yields from BocBMI are in the order of 30–60%. Only allo‐threonines without branching in the γ‐position are accessible by this method. In one case we have also applied this sequence of steps to prepare an α‐branched allo‐threonine derivative 26. – The 5‐acyl‐BocBMI derivatives 2–9 are remarkably stable to epimerization at the center between the two carbonyl groups. Possible reasons for this are discussed and are partially supported by an X‐ray crystal structure analysis of the phenacetyl derivative 6.
Synthesis of 11‐Membered Enediyne Ketones by the Intramolecular Nicholas Reaction
Authors: Maier Martin E. , Brandstetter Tilmann 
Published: July 2007

AbstractAn efficient route to 11‐membered enediyne ketones 13 and 22 was developed. This route is based on an intramolecular Nicholas reaction of 11 and 20, respectively. In the course of the preparation of the cyclization substrates 11 and 20, it was important to use the acetylenic alcohols 6 and 15 as building blocks for the construction of the cis‐enediynes 8 and 17, respectively, instead of the corresponding ketones which were converted into unstable acyclic enediynes. Some transformations of enediyne ketone 22 were also studied. For example, 22 could be transformed into the 2‐formyl compound 26 via the silyl enol ether 24. In addition, 24 was used for the preparation of the 2‐amino ketone 29.
Chemie der Ginkgolide, VI. Herstellung von 1,10‐Dihydroxy‐ und 1,7,10‐Trihydroxyginkgolid aus 1,3,7,10‐Tetrahydroxyginkgolid
Authors: Weinges Klaus , Rümmler Matthias , Schick Hartmut 
Published: July 2007

Chemistry of the Ginkgolides, VI. – Preparation of 1,10‐Dihydroxy‐ and 1,7,10‐Trihydroxyginkgolide from 1,3,7,10‐Tetrahydroxyginkgolide1,3,7,10‐Tetrahydroxyginkgolide (“ginkgolide C”, 1) which can be isolated in large quantities from the terpene fraction of Ginkgo leaves, can be converted into 1‐(tert‐butyldiphenylsilyloxy)‐3,7,10‐trihydroxyginkgolide (2) in 95% yield. 2 was converted via straightforward reactions into 1,7,10‐trihydroxyginkgolide (“ginkgolide M”, 9) and into the until now unknown 1,10‐dihydroxyginkgolide (15). 15 can also be obtained from 1,3,10‐trihydroxyginkgolide (“ginkgolide B”, 10). The intermediate products 14‐epiginkgolides 8 and 14 were epimerized to the ginkgolides with natural configuration at C‐14 by reaction with 4‐(dimethylamino)pyridine in acetonitrile. The title compounds are of interest for their possible activity as antagonists of the platelet activating factor (PAF).
De‐novo Synthesis of Enantiomerically Pure Deoxy‐ and Aminodeoxyfuranosides
Authors: Gräf Silke , Braum Manfred 
Published: July 2007

Abstract(R)‐3‐Hydroxy‐4‐pentenoic acid (2), readily available by an aldol addition of doubly deprotonated (R)‐2‐hydroxy‐1,2,2‐triphenylethyl acetate (1) to acrolein, functions as a key intermediate for the synthesis of enantiomerically pure deoxy‐and aminodeoxyfuranosides 8–13. Iodolactonization of the acid 2 enables the generation of the second stereogenic center and provides the furanone skeleton of 6a which is submitted to reduction and various functional‐group manipulations. Whereas the halogen atom of 7a is easily replaced by lithium azide in an SN2‐type reaction to deliver 10a, a free‐radical substitution pathway is suitable for the conversion of 7b into the glycoside 8a. The latter compound serves as an intermediate in a formal synthesis of 3′‐azido‐2′,3′‐dideoxythymidine (AZT). On the other hand, the triflate 7c is converted into the diazide 12 by a twofold nucleophilic substitution. The novel aminodeoxy‐furanosides 11 and 13 are available in enantiomerically pure from upon catalytic hydrogenation of the azides 10 and 12.
Proton Acid‐induced Rearrangements of α‐Alkynylestradiol Methyl Ethers
Authors: Pindur Ulf , Schall Thomas 
Published: July 2007

AbstractWhen subjected to proton catalysis, the α‐alkynylestradiol methyl ethers 1a and 1b furnish the Rupe or Meyer‐Schuster rearrangement products 2, 4, and 5a. In the presence of sulfuric acid, α‐ethynylestradiol 3‐methyl ether (1a) is converted into the D‐homosteroid 3a. The use of deuterated acids gives rise to the formation of the corresponding deuterated steroids 2b, 2c, 3b, and 5b. Some mechanistic implications of these results are also discussed.
Steroidal Cyclobutanones, IV. Heterocyclic Spiroannulation of 5α‐Cholestan‐3‐one. Stereospecific Beckmann Rearrangement of Steroidal 3‐Spirocyclobutanone Oximes
Authors: Blaszczyk Krzysztof , Paryzek Zdzislaw 
Published: July 2007

AbstractDiastereomeric 5α‐cholestane‐3,3′‐spiro‐2′,2′‐dichlorocyclobutanones 1 and 2 served as starting materials for the synthesis of related heterocyclic spirane derivatives. Thus, diastereomeric 5α‐cholestane‐3,3′‐spiropyrrolidin‐5′‐one (10, 11), ‐3′‐spiro‐γ‐lactone (12, 16), and ‐3′‐spirotetrahydrofuran (14, 18) are described. The spirocyclobutanone oximes (E)‐4 and (Z)‐5 and their O‐acetyl and O‐benzoyl derivatives 6, 7 and 8, 9 are also prepared. It has been shown that the Beckmann rearrangement of the spirocyclobutanone oximes 4 and 5 proceeds stereospecifically with exclusive anti migration. The stereochemistry of the spiro compounds is assigned on the basis of the 1H‐ and 13C‐NMR spectral data.
(1→4)‐β‐D‐Galaktosyltransferase läßt sich durch photolabile Liganden im Akzeptor‐Bindebereich spezifisch kovalent modifizieren
Authors: Lehmann Jochen , Petry Stefan 
Published: July 2007

The Acceptor Binding Area of (1→4)‐β‐D‐Galactosyltransferase Can Be Covalently Modified by Photoaffinity Labelling in the Presence of Photolabile LigandsThree spacer‐modified oligosaccharides (SMOs) 2, 3, and 4, consisting of two nonreducing GlcNAc end groups, O‐linked by an acyclic 10‐membered spacer carrying azi groups in positions 2, 3, or 5, proved to be acceptor substrates for (1→4)‐β‐D‐Galactosyltransferase (Gal‐T) and models of the natural biantennary core heptasaccharide of N‐glycoproteins. Photoaffinity labelling with each compound takes place with different efficiencies. This is an indication of regioselective chemical modification of the enzyme's extended binding area, because the reactive carbene in each case is placed in a different chemical surrounding. A radioactive SMO was used to prove the irreversible chemical modification of the acceptor binding site.
Total Synthesis of rac‐Silandrin, an Antihepatotoxic Flavanolignan
Authors: Antus Sándor , Baitz‐Gács Eszter , Gottsegen Agnes , Kovács Tibor , Szunyog József , Tóth Tamás S. , Wagner Hildebert 
Published: July 2007

AbstractThe first synthesis of racemic silandrin (rac‐1), which shows significant antihepatotoxic activity, has been accomplished via the key intermediate 9 prepared from the readily available starting materials caffeic acid ethyl ester (4) and coniferyl alcohol (5).
Reactions of 7‐(Methoxyimino)‐4‐methyl‐2H‐chromene‐2,8(7H)‐dione with Phosphorus Ylides. Synthesis of 2‐Substituted 6‐Methyl‐8H‐benzopyrano[7,8‐d]oxazol‐8‐ones
Authors: Bezergiannidou‐Balouctsi Catherine , Litians Konstantions E. , Malamidou‐Xenikaki Elizabeth , Nicolaides Demetrios N. 
Published: July 2007

Abstract7‐(Methoxyimino)‐4‐methyl‐2H‐chromene‐2,8(7H)‐dione (3) reacts with phosphonium salts 1a–c, 8a, b under phasetransfer catalysis conditions to afford the title 2‐substituted 6‐methylbenzopyranooxazol‐8‐ones 5a–c, 10a, b, respectively, along with compound 6, instead of the expected Wittig reaction products. However, the reaction of 3 with the stable phosphorus ylides 11a–c in addition to the corresponding benzopyranooxazoles 12a–c and compound 6 affords in the last case compound 16 as well according to a sequence involving an initial Wittig reaction between 11c and 3.
Pheromone Synthesis, CLVII. Synthesis of the Enantiomers of syn‐4‐Methyl‐5‐nonanol to Determine the Absolute Configuration of the Naturally Occurring (4S,5S) Isomer Isolated as the Male‐produced Pheromone Compound of Rhynchophorus vulneratus and Metamasius hemipterus
Authors: Mori Kenji , Kiyota Hiromasa , Malosse Christian , Rochat Didier 
Published: July 2007

AbstractThe enantioselective synthesis of both (4R,5R)‐ and (4S,5S)‐4‐methyl‐5‐nonanol (1) was achieved by starting from an optically active epoxide 5. A GC comparison on a chiral stationary phase of the synthetic enantiomers of 1 with the naturally occurring 1 was executed, and (4S,5S)‐1 was shown to be identical with the natural 1 isolated as the male‐produced pheromone compound of the weevils Rhynchophorus vulneratus and Metamasius hemipterus.
Studies on Heterocyclic Enaminonitriles, XIV. Preparation of Dihydrothiophenium‐1‐bis(ethoxycarbonyl)methylides and Their Recyclization with a Base
Authors: Yamagata Kenji , Takaki Mikiko , Ohkubo Kimiko , Yamazaki Motoyoshi 
Published: July 2007

AbstractThe reaction of 4,5‐dihydro‐2‐morpholino‐(2‐pyrrolidino and 2‐piperidino)‐3‐thiophenecarbonitriles 1–3 with bis‐(ethoxycarbonyl)carbenoid afforded stable dihydrothiophenium‐1‐bis(ethoxycarbonyl)methylides 4–6. The recyclization of compounds 4–6 with bases gave the corresponding diethyl 2,2(3H)‐thiophenedicarboxylates 7 and ethyl 2‐thiophenecarboxylates 7a′, 8, 9. The starting compounds 1–3 were synthesized by the reaction of 2‐amino‐4,5‐dihydro‐3‐thiophenecarbonitriles with morpholine, pyrrolidine, and piperidine.
Homochirale 2,4‐disubstituierte 1,3‐Dioxane aus (S)‐(−)‐Äpfelsäure: Stereoselektive Synthese und Untersuchung der NMDA‐Rezeptoraffinität aller vier Stereoisomerer
Authors: Wünsch Bernhard , Diekmann Heike , Höfner Georg 
Published: July 2007

Homochiral 2,4‐Disubstiuted 1,3‐Dioxanes from (S)‐(−)‐Malic Acid: Stereoselective Synthesis and Investigation of the NMDA Receptor Affinity of All Four StereoisomersStarting from a single enantiomerically pure compound, (S)‐(−)‐malic acid, all four stereoisomeric 4‐dimethylaminomethyl‐2‐phenyl‐1,3‐dioxanes (S,S)‐15 (S,R)‐16, and (R,S)‐16 are prepared: Transacetalisation of benzaldehyde dimethyl acetal (6b) with (S)‐(−)‐methyl 2,4‐dihydroxybutyrate (7a), which is obtained by chemoselective BH3 reduction of (S)‐(−)‐malic acid monoester 8b, yields the diastereomeric 1,3‐dioxane derivatives (S,S)‐10 and (R,S)‐11 in a 85:15 ratio. LDA deprotonation of (S,S)‐10 followed by protonation leads to C‐4 epimerisation [(S,S)‐10:(S,R)‐11 = 30:70]. The thermodynamically controlled 88:12 equilibrium of (R,R)‐10 and (S,R)‐11 is reached by treatment of (S,R)‐11 with acid. Aminolysis with dimethylamine and subsequent LiAlH4 reduction transform the four stereoisomeric esters (S,S)‐10, (R,R)‐10, (S,R)‐11 and (R,S)‐11 to give the amines (S,S)‐15, (R,R)‐15, (S,R)‐16 and (R,S)‐16, respectively. In the 3H‐(+)‐MK 801 displacement experiment (S,S)‐15, (R,R)‐15, (S,R)‐16 and (R,S)‐16 show a very little affinity to the phencyclidine binding site in the cation channel associated with the NMDA receptor.
Synthesis of the Hydroxyamino Sugar of Calicheamicins
Authors: Rainer Hildegard , Scharf Hans‐Dieter 
Published: July 2007

AbstractMethyl 6‐deoxy‐2,3‐O‐isopropylidene‐4‐O‐mesyl‐α‐D‐galactopyranoside (6) was prepared from D‐galactose in six steps. 6 was subjected to a nucleophilic displacement reaction with sodium azide as the nucleophile to yield methyl 4‐azido‐4,6‐dideoxy‐2,3‐O‐isopropylidene‐α‐D‐glucopyranoside (7) in 75% yield. Reduction of the azido group with NaBH4 afforded the amino sugar 8 (81%) which was adsorbed on silica gel and subsequently oxidized with ozone to methyl 4,6‐dideoxy‐2,3‐O‐isopropylidene‐4‐nitro‐α‐D‐glucopyranoside (10, 80%). This crystalline and stable compound 10 was reduced with Zn/NH4Cl to yield the desired methyl 4,6‐dideoxy‐4‐hydroxy‐amino‐2,3‐O‐isopropylidene‐α‐D‐glucopyranoside (11, 85%), which is unstable to air and therefore has to be transferred to its N,O‐diacetate derivate 12. No chromatographic purification was necessary.
Aminosäuren, 17 – Eine neue Synthese von Didehydrodipeptiden und Didehydrotripeptiden
Authors: Effenberger Franz , Kühlwein Jürgen , Hopf Martin , Stelzer Uwe 
Published: July 2007

Amino Acids, 17. – A New Synthesis of Didehydro Dipeptides and Didehydro TripeptidesEsters of N‐phthaloyl‐protected (R)‐ or (S)‐didehydro dipeptides 5–7 were obtained in good yields by the perrhenate‐catalyzed decomposition of 2‐azidocarboxylates 1 with N‐phthaloyl‐protected (R)‐ or (S)‐amino acid chlorides 2 in presence of at least equimolar amounts of N‐methyl‐2‐pyridone (4) as acylation catalyst. Esters of didehydro tripeptides 16 were obtained in a comparable procedure from the optically active amino acid chlorides 2 and 2‐(2‐azidoacyl)amino acid esters 15, which were prepared from 2‐azidocarboxylic acids 12 or the corresponding chlorides 13 with 2‐amino acid ester hydrochlorides (S)‐14. – As an example, the unprotected (S)‐alanly‐didehydrovalin 20 was prepared from the didehydro dipeptide 18a without any racemization by hydrolysis of the benzyl ester and subsequent hydrogenolytic removal of the N‐phthaloyl group.
Indolalkaloide, II. – Synthese von 4‐Amino‐tetrahydrocarbazol‐1‐on‐Derivaten
Authors: Patir Süleyman , Götz Peter H. 
Published: July 2007

Indole Alkaloids, II. – Synthesis of 4‐Amino‐tetrahydrocarbazol‐1‐one DerivativesTreatment of 1,2,3,4‐tetrahydrocarbazol‐1‐one with 1,2‐ethanedithiol gave the tetrahydrocarbazole 2 which was oxidized with DDQ to compound 3. It was converted into the imine 6 by treatment with n‐butylamine and ZnCl2. The imine was directly reduced with NaBH4 to give the amine 7, which was acetylated with benzoyl chloride to yield amide 8. Treatment of 8 with mercury(II) oxide and Et2O·BF3 gave 9.
F‐Säure‐haltige Phospholipidmoleküle in Zuckerrohrzellen
Authors: Scheinkönig Josef , Spiteller Gerhard 
Published: July 2007

F Acid‐Containing Phospholipids in Sugar Cane CellsHeterotrophic suspension cultures of sugar cane (Saccharum spec.) cells contain the F acids 1b–f. These acids are bound preferably to phosphatidylethanolamine 3 and phosphatidylcholine 4. Structures of F acid‐containing phospholipid molecular species 3b–d, 4b and 4c were established by enzymatic positional hydrolysis and GC/MS analysis of the respective (trimethylsilyl)diacylglycerol derivatives 5.
Neue Synthesen mit 1,3‐ambident‐nucleophilen Phosphor‐Yliden, VII. Heterocyclische Triphenylphosphonium‐chloride, Triphenylphosphonio‐olate, acyclische Triphenylphosphonio‐thiolate und ihre Wittig‐Derivate
Authors: Capuano Lilly , Drescher Stefan , Huch Volker 
Published: July 2007

Syntheses with 1,3‐Ambident‐Nucleophilic Phosphorus Ylides, VII. – Heterocyclic Triphenylphosphonium Chlorides, Triphenylphosphonio‐Olates, Acyclic Triphenylphosphonio‐Thiolates and Their Wittig DerivativesUnder mild conditions, benzoylmethylenetriphenylphosphorane (1b) reacts readily with oxalyl chloride to give the unstable 4‐(4,5‐dihydro‐4,5‐dioxo‐2‐phenyl‐3‐furyl)triphenylphosphonium chloride (3b). This undergoes rapid hydrolysis to afford the triphenylphosphonium chloride 4 of benzoylpyruvic acid. Thermolysis of 3b or 4 results in the formation of 2‐(triphenylphosphoranyliden)indan‐1,3‐dione (10), the structure of which was established by X‐ray diffraction analysis. – With phenylmalonyl chloride, the title compounds 1a, b, d react by formation of the triphenylphosphonio‐olates 7 of pyridine‐, pyran‐ and thiopyran‐dione, respectively. – The (thioaroylmethylene)triphenylphosphoranes 1e, f react with benzonitrile imine 12 to give the red hydrazonotriphenylphosphoniothiolates 16, the structures of which have been elucidated by an X‐ray diffraction analysis. Under rigorous conditions, compounds 16 undergo an intramolecular Wittig‐type reaction leading to pyrazoles 14.
Synthesis of enantiomerically pure indoloquinolizine derivatives
Authors: Shiqi Peng , Li Zhang , Mengshen Cai , Winterfeldt Ekkehard 
Published: July 2007

AbstractL‐Tryptophan methyl ester reacts with 1,1,3,3‐tetramethoxypropane to give methyl carbolinecarboxylate 2 as a 1:2 mixture of the (1R,3S) and (1S,3S) stereoisomers. Conversion to the corresponding amides (1R,3S)‐3 and (1S,3S)‐3 was accomplished by treatment of 2 with ammonia. Benzylation of (1R,3S)‐3 or (1S,3S)‐3 afforded the corresponding 2‐benzylcarbolineamide (1R,3S)‐4 or (1S,3S)‐4. Dehydration of the amide group in (1R,3S)‐4 or (1S,3S)‐4 yielded the corresponding 2‐benzylcarbolinenitrile (1R,3S)‐5 or (1S,3S)‐5, which was treated with NaBH4 to reductively remove the cyano group. Hydrogenation removed the benzyl‐protectin group of 6 resulting in (1R)‐7 or (1S)‐7, which is then alkylated with methyl vinyl ketone to give the Michael adduct (1R)‐8 or (1S)‐8. Subsequent Aldol reaction and dehydration afforded the enantiomerically pure indoloquinolizine derivatives (12bR)‐9 or (12bS)‐9, which was shown to be enantiomerically pure by recording their 1H‐NMR spectra in the presence of a chiral shift reagent.
Synthese von Manzamin C, Infractin und 6‐Hydroxyinfractin
Authors: Nowak Wolfgang , Gerlach Hans 
Published: July 2007

Synthesis of Manzamine C, Infractine and 6‐HydroxyinfractineManzamine C (1), a β‐carboline alkaloid with antitumor activity isolated from the marine sponge Haliclona sp. was synthesized. The dilithium derivative of 5‐hexynoic acid (6) was alkylated with 7 to give after esterification the methyl 10‐hydroxy‐5‐decynoate (8). The tosylate of 8 was converted into the azide 9 which could be selectively hydrogenated with Lindlar palladium catalyst to give the amino ester 10. Saponification of 10 and acylation with (Boc)2O yielded 11, which was converted with pentafluorophenol into 12. Removal of the Boc group in 12 gave an amino ester as intermediate, which cyclized immediately under high dilution conditions to give the lactam 13 in high yield. Reduction of 13 with LiAlH4 produced the macrocyclic amine 4. The β‐carboline part of 1 was prepared by condensation of N‐benzyltryptamine 14 with the formylacetic acid equivalent 15 to give 16. Dehydrogenation of 16 with Pd‐on‐carbon catalyst led to the orthoester 17, which could be converted into the methyl ester 5 in high overall yield. The 4‐(dimethylamino)pyridine‐catalyzed substitution of the methyl ester function in 5 by the amine 4 gave the amide 29. The analogous reaction of 5 with pyrrolidine or with azacyclotridecane yielded 30 and 31. Reduction of these three amides with LiAlH4 produced 1, 2 and 3. The spectroscopic properties of 1 were identical with those of natural manzamine C. – Condensation of 14 or N‐benzyl‐5‐(benzyloxy)tryptamine (19) with aldehyde 18 yielded the products 20 and 21, which could be dehydrogenated to furnish 22 and 23. From these the methyl esters 24 and 25 with properties identical to those of the known β‐carboline alkaloids infractine and 6‐hydroxyinfractine could be obtained.
Free‐radical Cyclization of Petroselinic Acid
Authors: Metzger Jürgen O. , Mahler Ralf 
Published: July 2007

AbstractPetroselinic acid was cyclized via methyl 2‐iodopetroselinate (1) with tributyltin hydride to give methyl trans‐ and cis‐2‐dodecyl‐1‐cyclopentanecarboxylate (2). The atom‐transfer method with hexabutylditin resulted in the formation of bicyclic γ‐lactones 4 and methyl trans‐2‐(1′‐iodododecyl)‐1‐cyclopentanecarboxylate (trans‐5). The same products were obtained with the new initiator system SnCl2/AgOAc. This method showed, if compared with the other methods, the shortest reaction time, the highest yield and stereoselectivity combined with a very simple workup procedure and the use of less toxic chemicals.
Syntheses and Cardiovascular Activity of Stereoisomers and Derivatives of Eburnane Alkaloids
Authors: Czibula László , Nemes András , Visky György , Farkas Mária , Szombathelyi Zsolt , Kárpáti Egon , Sohár Pál , Kessel Martin , Kreidl János 
Published: July 2007

AbstractThe synthesis of all the possible isomers of the eburnameninevincamine type alkaloids 1b, 2a, 3a and derivatives 4, 8, 9, 10 is described. Structures were determined by 1H‐ and 13C‐NMR spectroscopy including special techniques such as DR, DEPT, DNOE, and 2D‐HSC. In contrast to the known cerebrovascular effects of cis‐(3S,16S) compounds, trans‐(3S,16R) derivatives show a significant peripheral vasodilator effect.
Herkunft des Kohlenstoff‐Grundskeletts von F‐Säuren
Authors: Scheinkönig Josef , Spiteller Gerhard 
Published: July 2007

Origin of the Basic Carbon Chain of F AcidsFeeding experiments with sodium [2‐13C]acetate on suspension cultures of Saccharum spec. show that the basic carbon chain of F acids 1 is derived from acetate units via the fatty acid pathway. Incorporation of 13C label was confirmed by GC/MS analysis of the corresponding tetrahydrofuran derivatives 2.
Unexpected Formation of 3,6‐Anhydrofuranoses by Acid Treatment of Methyl 2,3‐Di‐O‐acyl‐D‐glycopyranosides
Authors: Ziegler Thomas , Vollmer Martin , Oberhoffner Sven , Eckhardt Elisabeth 
Published: July 2007

AbstractTreatment of methyl 2,3‐di‐O‐acyl‐D‐glycopyranosides 1 of glucose and mannose with catalytic amounts of trifluoromethanesulfonic acid afforded the corresponding bis(5‐O‐acyl‐3,6‐anhydro‐D‐glycofuranose) 1,2′:2,1′‐dianhydrides 6 in 12–58% yield the structure of which was confirmed for the α‐D‐glucose derivative 6a by an X‐ray analysis. In addition, in the presence of methyl pyruvate (2a) or methyl 2‐acetoxy‐acrylate (2b) various amounts of diastereomeric 3,6‐anhydro‐5‐O‐benzoyl‐1,2‐O‐(1‐methoxycarbonyl)ethylidene‐α‐D‐glucofuranoses 5 and acylated methyl α‐D‐glucopyranosides 3 and 4, respectively, were formed.
Darstellung von (3‐Amino‐1‐alkenyl)phosphonsäuren aus allylischen α‐ und γ‐Hydroxyphosphonaten. Sigmatrope Umlagerung von (1‐Azido‐2‐alkenyl)phosphonsäureestern
Authors: Öhler Elisabeth , Kotzinger Silvia 
Published: July 2007

Synthesis of (3‐Amino‐1‐alkenyl)phosphonic Acids from Allylic α‐ and γ‐Hydroxyphosphonates. – Sigmatropic Rearrangement of Dialkyl (1‐Azido‐2‐alkenyl)phosphonates(3‐Azido‐1‐alkenyl)phosphonates 8 with R1 = H are prepared regioselectively by reaction of secondary (1‐hydroxy‐2‐alkenyl)phosphonates 3 with TPP/DEAD/HN3 and subsequent thermal 1,3‐rearrangement of the allylic α‐azidophosphonates 5 primarily formed. (3‐Azido‐1‐alkenyl)phosphonates 8 with R1 ≠ H are conveniently obtained from the regioisomeric tertiary 3‐hydroxy derivatives 4, which can be prepared either by allylic rearrangement of the corresponding α‐hydroxyphosphonates 3, or by NaBH4 reduction of the (3‐oxo‐1‐alkenyl) derivatives 7. The synthetic utility of the azido compounds 8 is demonstrated by their conversion into the (3‐amino‐1‐alkenyl)phosphonic acids 11 and the N,O‐protected derivatives 12 and 13, and to the saturated γ‐aminophosphonates 14.
Alkaloide aus Veratrum patulum, I. Isolierung und Strukturaufklärung neuer Steroidalkaloidglycoside
Authors: Irsch Eva‐Maria , Pachaly Peter , Breitmaier Eberhard , Sin Kwan‐Seog 
Published: July 2007

Alkaloids from Veratrum patulum, I. – Isolation and Structure Elucidation of New Steroid Alkaloid GlycosidesHerrn Professor Dr. F. Zymalkowski zum 80. Geburtstag gewidmet.
Beside the known veratrosine (1), two new steroid alkaloid glucosides, 23‐O‐β‐D‐glucopyranosyl‐20‐isoveratramine (2) and (22S,23R,25S)‐23‐O‐β‐D‐glucopyranosyl‐5,11,13‐veratratrienine‐3β,23‐diol (3), were isolated from the roots of Veratrum patulum Loes. fil. (Liliaceae) and characterized by spectroscopic methods.