bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Functionalized 1,2,3,4‐Tetrahydro‐β‐carbolines from Enamino Ketones
Authors: Tietze Lutz F. , Wichmann Jürgen 
Published: July 2007

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

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

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

Cytochrome P‐450 Model Reactions, 2. — Isolation and Characterization of a Manganese(IV)‐Pentafluoroiodosylbenzene‐Porphinato Complex as a Model of the Active Species of the Catalytic Cycle of Cytochrome P‐450The isolation at −78°C and characterization of the crystalline reactive manganese(IV)‐porphinato complex Mn(TDCPP)‐(C6F5IOCl)Cl (4) is described. 4 is compared with the manganese(IV)‐porphinato complexes Mn(TDCPP)(C6H5IOCl)2 (2) and Mn(TDCPP)(OCH3)2 (3). The stoichiometric reaction of 4 with triphenylphosphane yields 1.5 equivalents of triphenylphosphane oxide, 1.0 equivalents of Mn(TDCPP)Cl (1), and 1.0 equivalents of pentafluoro‐iodobenzene. 4 epoxidizes stilbene, oxygenates cyclohexane, and oxidizes anthracene to anthraquinone.
Studies on Heterocyclic Enaminonitriles, XII. Reactions of 4,5‐Dihydro‐2‐morpholino‐ (and ‐2‐pyrrolidino)‐3‐furancarbonitriles with Dichlorocarbene
Authors: Yamagata Kenji , Takaki Mikiko , Yamazaki Motoyoshi 
Published: July 2007

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

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

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

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

Photochemical Studies, 64. — Photostability of Glucocorticoids in the Solid StateMost of the pharmacopoeia require that the glucocorticoids hydrocortisone (1), cortisone (2), hydrocortisone 21‐acetate (3) and cortisone 21‐acetate (4) must be protected from light during storage. The present study shows that UV irradiation of these compounds in the solid state leads to the loss of the side chain at C‐17. Two 17‐ketosteroids, 11β‐hydroxy‐4‐androstene‐3,17‐dione (6) and 4‐androstene‐3,11,17‐trione (7), were obtained as photoproducts (yields 3% and 4%, respectively).
Arene Hydrides, 10 Michael Additions of Anthracene Hydride. Selective Reduction of the ArCC Moiety by Fragmentation of the Michael Adduct
Authors: Sommer Andreas , Stamm Helmut 
Published: July 2007

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

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

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

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

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

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

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

AbstractThe sodium tetrahydroborate reduction of 16‐<[acetyl(alkyl)‐amino]methylene>‐17‐ketosteroids 1aa, 2aa and 2ba affords (Z)‐16‐ and (E)‐16‐<[acetyl(alkyl)amino]methylene>‐17β‐hydroxysteroids (Z)‐3, (E)‐3, (Z)‐4b, (Z)‐4a, (Z)‐5c and (E)‐5a. The N‐acetyl group of the (Z) isomers (Z)‐3, (Z)‐4b, and (Z)‐5c migrates to the 17β‐hydroxyl in inert solvents, and the products suffer secondary transformation into unsaturated aldehydes 6 and 9a; intermediate 8 has been isolated. The (E) isomers (E)‐3, and (E)‐5a do not change, even not under more drastic conditions.
Synthese linearer und verzweigter perfluoralkylierter Carbonsäuren durch radikalische Addition von Perfluoralkyliodiden an ungesättigte Fettsäuren
Authors: Metzger Jürgen O. , Linker Ursula 
Published: July 2007

Synthesis of Linear and Branched Perfluoroalkylated Carboxylic Acids by Radical Addition of Perfluoroalkyl Iodides to Unsaturated Fatty AcidsLinear and branched perfluoroalkylated carboxylic acids, i.e. 6a, 11a, 12a, 15a and 16a, are easily available by tin(II) chloride/silver(I) acetate‐initiated free radical additions of perfluoroalkyl iodides to unsaturated carboxylic acids 1a–3a followed by tributylstannan reduction of the respective addition products. The unsaturated perfluoroalkylated carboxylic acids 7a can be obtained by regioselective base‐catalyzed elimination of HI from the addition products.
Glycosyl Imidates, 52. Synthesis of Globotriaosylceramide (Gb3) and Isoglobotriaosylceramide (isoGb3)
Authors: Qiu Dongxu , Schmidt Richard R. 
Published: July 2007

AbstractThe synthesis of globotriaosylceramide (1) was based on O‐galactosyl trichloroacetimidate 5α as donor and 4b‐O‐unprotected lactose 7 as acceptor; 7 was readily accessible from lactose. Glycosylation by an “inverted procedure” afforded preferentially the α‐trisaccharide 8α. Its transformation into the O‐acetyl‐protected trichloroacetimidate 11α led to an efficient triaosyl donor for the β‐selective glycosylation of 3‐O‐benzoyl‐azidosphingosine 12. The obtained lysoglycosphingolipid derivative 13 was directly converted into the N‐palmitoyl derivative 14 which gave upon O‐deacylation the target molecule 1. For the synthesis of isoglobotriaosylceramide (2) essentially the same procedure was applied. Thus, by starting from 5α and 3b, 4b‐O‐unprotected lactose acceptor 15 the use of the inverted procedure for glycoside‐bond formation gave preferentially trisaccharide 16α, which was transformed into triaosyl donor 24α. Application of the azidosphingosine glycosylation procedure afforded lysosphingolipid 25 and subsequently glycosphingolipid 26; after deprotection the target molecule 2 was obtained.
Novel Concepts in Directed Biaryl Synthesis, IX. Synthesis and Structure of Benzonaphthopyranones, Useful Bridged Model Precursors for Stereoselective Biaryl Syntheses
Authors: Bringmann Gerhard , Hartung Thomas , Göbel Lothar , Schupp Olaf , Ewers Christian L. J. , Schöner Bernd , Zagst Rainer , Peters Karl , von Schnering Hans Georg , Burschka Christian 
Published: July 2007

AbstractA practicable two‐step procedure for the preparation of a series of lactone‐type bridged biaryls 7 as favorable substrates for subsequent atropisomer‐selective ring‐opening reactions is described. Due to the efficiency of the coupling step, which tolerates even a tert‐butyl group next to the biaryl axis and avoids problems of regioselectivity, a variety of differently substituted representatives is prepared. These cover a broad range of steric hindrance and thus molecular distortion. The structures are investigated mainly by NMR spectroscopy and X‐ray diffraction, showing the lactones 7 to be helically distorted, depending on the size of the residues R.
Synthesis of Amines and Amino Alcohols by Electrophilic Amination and Highly Stereoselective Reduction
Authors: Gmeiner Peter , Bollinger Bernd 
Published: July 2007

AbstractA practical and selective method for the synthesis of the β‐arylamines 5 and the cis‐ or trans‐amino alcohols 8 or 11 is reported. The reaction sequence starts from α‐tetralones 1 which readily react with dibenzyl azodicarboxylate to afford the protected α‐hydrazino ketones 2. Then, depending on the reduction conditions, the trans‐hydrazino alcohols 10 or the cis isomers 7 are formed predominantly. The stereoselectivities which range between 18:1 and 1:67 (trans/cis) are explained by stereoelectronic effects (σ,σ interactions) and steric hindrance. Depending on the workup procedure, we can control, whether the cis‐hydrazino alcohols 7 or the oxazolidinone derivatives 3 are isolated. Subsequent hydrogenolyses of 4, 7 and 10 lead to the target molecules 5, 8 and 11, respectively.
Unusual Rearrangement in the Dehydration of Aroylated Butanodihydrazides
Authors: Tashtoush Hasan , Al‐Talib Mahmoud , Odeh Nedal 
Published: July 2007

AbstractDehydration of N,N′‐diaroylbutanodihydrazides 3a–f with phosphoryl chloride gave, unexpectedly, 2,5‐diaryl‐1,3,4‐oxadiazoles 4a–f. However, dehydration of N,N′‐dialkanoylbutanodihydrazides 1a–c afforded 5,5′‐dialkyl‐2,2′‐(1,2‐ethandiyl)‐bis(1,3,4‐oxadiazoles) 2a–c.
A Bisnitroxyl Dipeptide
Authors: Dulog Lothar , Wang Wei 
Published: July 2007

AbstractThe dinitroxylamide 8 is synthesized from the monomer 4‐amino‐4‐carboxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (2). The benzyloxycarbonyl group as amino protective group and the methoxy group as carboxyl protective group have been introduced. The acylation of compound 3 with compound 4 is carried out in the presence of dicyclohexylcarbodiimide. After deprotection the dinitroxylamide 8 is obtained.
Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate
Authors: Mihailović Mihailo Lj. , Vukićević Rastko , Konstantinović Stanimir , Milosavljević Slobodan , Schroth Gerhard 
Published: July 2007

AbstractReactions of some primary and secondary Δ4‐, Δ5‐ and Δ6‐alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated. When terminally unsubstituted Δ4‐alkenols, such as 4‐penten‐1‐ol (5a) and 5‐hexen‐2‐ol (5b), are treated with TTA in benzene, β‐acetoxylated tetrahydrofurans 8a and 8b are obtained. However, when the reaction is carried in acetic acid the products are both regioisomers, i.e. five‐ and six‐membered cyclic ethers (8a, 8b, 7a and 7b). 4‐Methyl‐4‐penten‐1‐ol (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7c is predominant, and in acetic acid it is the sole cyclization product. Terminally dialkylated alkenols, such as 5‐methyl‐4‐hexen‐1‐ol (1b) and 6‐methyl‐5‐hepten‐2‐ol (1c), are converted into β‐acetoxylated (4b and 4c) and unsaturated cyclic ethers (9a and 9b), in both cases of the tetrahydrofuran type. 5‐Hexen‐1‐ol (10) and 6‐hepten‐1‐ol (11) cyclize to the corresponding six‐ (13) and seven‐membered cyclic ether (14), respectively. Organothallium intermediates have been isolated and identified in the cases of alcohols 5a, 5c and 10, proving that the TTA addition to the double bond has originally obeyed the Markovnikov rule.
Zur Synthese von (Z)‐ und (E)‐3‐(1H‐Imidazol‐4‐yl)‐2‐propenamin und einigen 3‐(1H‐Imidazol‐4‐yl)propanaminen
Authors: Sellier Christian , Buschauer Armin , Elz Sigurd , Schunack Walter 
Published: July 2007

Synthesis of (Z)‐ and (E)‐3‐(1H‐imidazol‐4‐yl)‐2‐propenamine and Some 3‐(1H‐imidazol‐4‐yl)propanamines3‐(1H‐Imidazol‐4‐yl)propanamine (6, homohistamine), an essential intermediate for the synthesis of potent impromidine‐type histamine H2 receptor agonists, is efficiently prepared from trans‐urocanic acid (1) by reduction of the methyl ester 2 and conversion to the saturated amide 4. Dehydration with thionyl chloride yields the nitrile 5 which is subsequently reduced to 6. Side‐chain methylated 3‐(1H‐imidazol‐4‐yl)propanamines 12 are available from 1H‐imidazole‐4‐carbaldehyde (7) and 1‐(1H‐imidazol‐4‐yl)ethanone (8), respectively, via unsaturated nitriles 10 and stepwise reduction. Cyclization of the appropriate 4‐bromo‐5‐oxohexanenitriles 14α with formamidine in liquid ammonia and reduction of the obtained nitriles 15 furnishes ring‐methylated amines 16. (E)‐3‐(1H‐Imidazol‐4‐yl)‐2‐propenamine [(E)‐23] is obtained in six steps from the trans‐ester 2 while (Z)‐23 is accessible by treating 7 with triphenyl(2‐phthalimidoethyl)phosphonium bromide (17) and final deprotection. These primary amines are valuable intermediates for the synthesis of impromidine analogues.
Spiroketal Synthesis. — A Case of Intramolecular Glycoside Bond Formation
Authors: Preuss Rainer , Jung Karl‐Heinz , Schmidt Richard R. 
Published: July 2007

AbstractFrom 4‐O‐unsubstituted glucose derivatives 1a, b the 4‐hydroxymethyl‐substituted glucose derivatives 9a, b were obtained via oxidation to the ketone, Wittig reaction with methylenetriphenylphosphorane, borane addition, and subsequent oxidation to yield the diastereomeric galactose‐derived compounds 5a, b; the required inversion of configuration at C‐4 was accomplished through oxidation to the formyl derivatives, base‐catalyzed isomerisation, and then reduction. Transformation of hydroxymethyl derivatives 9a, b into the iodo derivatives 11a, b and reaction with n‐butyllithium generated the C‐lithiated species 11aA, bA which furnished with O‐benzyl‐protected gluconolactone 12 the ketose derivatives 13a, b. Treatment with Et2O–BF3 afforded under concomitant 6‐O‐debenzylation the spiroketals 15a, b. Hydrogenolytic O‐debenzylation and subsequent O‐acetylation led to compounds 16a and 16b, respectively. The anomeric ketoside configuration was derived from NOE experiments.
Studien zur Chemie von O,N‐ und S,N‐haltigen Heterocyclen, 13. Untersuchungen zur Ringverengung von 1,5‐Benzothiazepinen zu 1,4‐Benzothiazinen
Authors: Erker Thomas , Bartsch Herbert 
Published: July 2007

Studies on the Chemistry of O,N‐ and S,N‐Containing Heterocycles, 13. — Investigations on the Ring Contraction of 1,5‐Benzothiazepines to 1,4‐BenzothiazinesReaction of the (3R)‐1,5‐benzothiazepinon derivative 5 with NaNO2 in glacial acetic acid leads to the rac‐1,4‐benzothiazinone derivatives 6a and 7. Furthermore, reaction of 5 with NaNO2 in sulphuric acid/KBr yields the ring‐contracted compound rac‐6b. Compound 8, after heating with thionyl chloride, affords the E/Z isomeres 9 and 10.
Syntheses and Reactions of 2,2‐Disubstituted Cyclopentane‐1,3‐diones, 6. Conversion of 2‐Methylcyclopentane‐1,3‐dione into 5‐Methylcycloheptane‐1,4‐dione via 3‐(1‐Methyl‐2,5‐dioxocyclopentyl)propanal
Authors: Schick Hans , Roatsch Birgit , Schwarz Hartmut , Hauser André , Schwarz Sigfrid 
Published: July 2007

AbstractIn contrast to earlier reported unsuccessful experiments the Michael addition of prop‐2‐enal to 2‐methylcyclopentane‐1,3‐dione (1) affords 3‐(1‐methyl‐2,5‐dioxocyclopentyl)propanal (3) in 90% yield, if the reaction is carried out in water without a basic catalyst. This aldehyde is converted by an intramolecular aldol reaction to (±)‐endo‐2‐ and (±)‐exo‐2‐hydroxy‐5‐methylbicyclo[3.2.1]octane‐6,8‐dione (rac‐4 and rac‐6), both affording (±)‐5‐methylcycloheptane‐1,4‐dione (rac‐8) after oxidation to (±)‐5‐methylbicyclo[3.2.1]octane‐2,6,8‐trione (rac‐2), hydrolytic ring‐opening and decarboxylation. This reaction sequence allows the transformation of the 2‐alkylated cyclopentane‐1,3‐dione 1 into the 5‐alkylated cycloheptane‐1,4‐dione rac‐8 in a good overall yield. The pathway of the ringopening process has been determined by an investigation of the reaction intermediates.