bluuebunny/crossref_metadata_2025_split huggingface dataset:
Säure‐Additionen an ‘Push‐Pull’‐Enine. Erste Beobachtung einer Umlagerung von 5‐Chloro‐5‐(dialkylamino)pentadienalen
Authors: Berger Daniel , Neuenschwander Markus 
Published: December 2004

Reaction of ‘Push‐Pull’ Enynes with Acids. First Observation of a Rearrangement of 5‐Chloro‐5‐(dialkylamino)pentadienals‘Push‐pull’‐enynes 7 react easily with HCl as well as with AcOH to give 5‐amino‐5‐chloropentadienals 8 and 5‐(acetoxy)‐5‐aminopentadienals 13 as well as the corresponding ketones. In view of a postulated rearrangement of compounds 8 and 13 (Scheme 2), both types of compounds have been treated with traces of acid. While no definite reaction is observed in case of 13, HCl‐addition products 8 easily and quantitatively rearrange to give 2H‐pyran‐2‐iminium chlorides 10 which are the postulated intermediates of the rearrangement 8→12 (Scheme 2).
A Novel Amination Reaction with Diphenyl Phosphorazidate: Synthesis of α‐amino‐acid derivatives
Authors: Villalgordo José M. , Linden Anthony , Heimgartner Heinz 
Published: December 2004

AbstractThe reaction of enolates of α‐unsubstituted carboxamides 3 with diphenyl phosphorazidate (DPPA) and di(tert‐butyl) dicarbonate (‘Boc anhydride’) in THF at −78° yielded 2‐{[(tert‐butoxy)carbonyl]amino}carboxamides 5 (Scheme 2) which are derivatives of α‐amino acids. In this reaction, DPPA acts as an electrophilic amination reagent. A reaction mechanism is proposed in Scheme 3.
Epoxyfocardin and Its Putative Biogenetic Precursor, Focardin, Bioactive, New‐Skeleton Diterpenoids of the Marine Ciliate Euplotes focardii from Antractica
Authors: Guella Graziano , Pietra Francesco , Dini Fernando 
Published: December 2004

AbstractFrom the ciliate Euplotes focardii, collected from Ross Sea coastal waters, Antarctica, a new‐skeleton diterpenoid, epoxyfocardin, was isolated as a 85:15 mixture of hemiacetals 8a and 8b. The absolute configuration of 8a/8b was determined from Mosher's esters 11a/11b and 12a/12b. Focardin 9a/9b, most likely a biogenetic precursor of 8a/8b, was also isolated as a minor component. Focardin, and particularly epoxyfocardin, proved to be toxic towards representatives of ciliate communities from Antarctic, temperate, tropical, and equatorial environments, constituting the first example of ecologically relevant metabolites from ciliate species that inhabit polar ecosystems.
Synthesis of Coumarin Derivatives as Inhibitors of Platelet Aggregation
Authors: Chen Yeh‐Long , Wang Tai‐Chi , Lee Kuan‐Han , Tzeng Cherng‐Chyi , Chang Ya‐Ling , Teng Che‐Ming 
Published: December 2004

AbstractIn a search for the inhibitors of platelet aggregation, certain coumarin derivatives were synthesized and evaluated for antiplatelet activity against thrombin(Thr)‐, arachidonic acid(AA)‐, collagen(Col)‐, and platelet‐activating‐factor(PAF)‐induced aggregation in washed rabbit platelets. These compounds were synthesized from 4‐hydroxycoumarin (1) or naphthalen‐1‐ol via alkylation and Reformatsky‐type condensation (Schemes 1–3). Among them, 4‐[(2,3,4,5‐tetrahydro‐4‐methylidene‐5‐oxo‐2‐phenylfuran‐2‐yl)methoxy]‐2H‐1‐benzopyran‐2‐one (6b) showed potent antiplatelet effects on AA‐ and PAF‐induced aggregation with IC50 values of 8.21 and 103.67 m̈M, respectively (see Tables 1 and 2). The antiplatelet potency of 6b against PAF‐induced aggregation could be further improved by introducing a proper substituent at the 2‐phenyl group of the lactone ring.
Dendrophanes: Novel Steroid‐Recognizing Dendritic Receptors. Preliminary Communication
Authors: Wallimann Peter , Seiler Paul , Diederich François 
Published: December 2004

AbstractThe H2O‐soluble dendritic cyclophanes (dendrophanes) 3–5 of first to third generation with molecular weights up to nearly 20 kD were synthesized, purified, and characterized. Cyclophane 2, which served as the initiator core (generation zero), was prepared from tetrabromocyclophane 10 in a four‐step sequence which involved as the first transformation a high‐yielding, four‐fold Pd(0)‐catalyzed Suzuki cross‐coupling reaction with 4‐(benzyloxy)‐phenyl‐boronic acid to give 18. The X‐ray crystal‐structure analysis of tetrabromocyclophane 10 displayed an open, nearly rectangular box with opposite aromatic walls being 8.3 and 11.4 Å apart and of suitable size for the incorporation of steroidal substrates. 1H‐NMR Binding titrations in borate‐buffered D2O/CD3OD 1:1 showed that cyclophane‐tetracarboxylate 2 forms 1:1 inclusion complexes with steroids (Table 2). Complexation was found to be enthalpically driven with higher binding affinities measured for the more apolar substrates. 1H‐NMR Titrations in the same solvent also provided clear evidence for core‐selective complexation of testosterone (21) by the dendrophanes 3 (1st), 4 (2nd), and 5 (3rd generation) carrying up to 108 carboxylate surface groups. The stability of the corresponding 1:1 complexes was hardly affected by the size of the dendritic shell, although some generation‐dependent conformational changes in the receptor cavity seemed to take place. Remarkably, host‐guest exchange kinetics in all recognition processes were fast on the 1H‐NMR time scale.
Synthesis and Luminescence of Novel EuIII Complexing Agents and Labels with 4‐(Phenylethynyl)pyridine Subunits
Authors: Takalo Harri , Hemmilä Ilkka , Sutela Timo , Latva Martti 
Published: December 2004

AbstractThe synthesis of novel 4‐(phenylethynyl)pyridine subunits containing H2O‐soluble complexing agents and their luminescence with EuIII ions are reported. Ligands with high luminescence intensities as well as quantum yields were obtained. Also the prepared labeling reagents as antibody conjugates gave the highest quantum and luminescence yields reported for H2O‐soluble EuIII labels.
1,5‐Dipolare Elektrocyclisierung von Acyl‐substituierten ‘Thiocarbonyl‐yliden’ zu 1,3‐Oxathiolen
Authors: Kägi Martin , Linden Anthony , Heimgartner Heinz , Mlostoń Grzegorz 
Published: December 2004

1,5‐Dipolar Electrocyclization of Acyl‐Substituted ‘Thiocarbonyl‐ylides’ to 1,3‐OxathiolesThe reaction of α‐diazoketones 15a, b with 4,4‐disubstituted 1,3‐thiazole‐5(4H)‐thiones 6 (Scheme 3), adamantanethione (17), 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (19; Scheme 4), and thiobenzophenone (22; Scheme 5), respectively, at 50–90° gave the corresponding 1,3‐oxathiole derivatives as the sole products in high yields. This reaction opens a convenient access to this type of five‐membered heterocycles. The structures of three of the products, namely 16c, 16f, and 20b, were established by X‐ray crystallography. The key‐step of the proposed reaction mechanism is a 1,5‐dipolar electrocyclization of an acyl‐substituted ‘thiocarbonyl‐ylide’ (cf. Scheme 6). The analogous reaction of 15a, b with 9H‐xanthen‐9‐thione (24a) and 9H‐thioxanthen‐9‐thione (24b) yielded α,β‐unsaturated ketones of type 25 (Scheme 5). The structures of 25a and 25c were also established by X‐ray crystallography. The formation of 25 proceeds via a 1,3‐dipolar electrocyclization to a thiirane intermediate (Scheme 6) and desulfurization. From the reaction of 15a with 24b in THF at 50°, the intermediate 26 (Scheme 5) was isolated. In the crude mixtures of the reactions of 15a with 17 and 19, a minor product containing a CHO group was observed by IR and NMR spectroscopy. In the case of 19, this side product could be isolated and was characterized by X‐ray crystallography to be 21 (Scheme 4). It was shown that 21 is formed – in relatively low yield – from 20a. Formally, the transformation is an oxidative cleavage of the CC bond, but the reaction mechanism is still not known.
Chemistry and the Origin of Life
Authors: Eschenmoser Albert , Volkan Kisakürek M. 
Published: December 2004

AbstractThe natural genesis of life on Earth is a hypothesis of evolutionary science; it is the task of synthetic organic chemistry to test this hypothesis experimentally. The aim of an experimental aetiological chemistry is not primarily to delineate the pathways along which our (‘natural’) life on Earth could have originated, but to provide decisive experimental evidence, through the realization of model systems (‘artificial chemical life’), that life can arise as a result of the organization of organic matter.
A Reinvestigation of the Oxidative Rearrangement of Yohimbane‐Type Alkaloids. Part B. Formation of Oxindol (= 1,3‐Dihydro‐2H‐indol‐2‐one) Derivatives
Authors: Stahl Reto , Borschberg Hans‐Jürg , Acklin Pierre 
Published: December 2004

AbstractThe methanolysis of the epimeric 7‐chloro‐7H‐yohimbine derivatives 2 and 3 was reinvestigated. In case of the 7α‐epimer 2, the reaction was uneventful and conformed with earlier observations, i.e., under sufficiently mild conditions, only the imino ether 4 (= imino ether A) was produced. Under the same conditions, the less reactive β‐isomer 3 furnished a mixture of both imino ethers 4 and 5, accompanied by the elimination product 11, and by equal amounts of yohimbine (1) and 3,4,5,6‐tetradehydroyohimbine (12), which are believed to arise through a disproportionation process of the putative intermediate 5,6‐didehydroyhimbine (23). The nature of this divergent reactivity and of the ready equilibration of 4 and 5 was investigated by means of extensive force‐field and semi‐empirical calculations (AM1 and PM3) of various conformers of the compounds 2–5 and of some possible reaction intermediates.
Intramolecular Vinyl Radical Cyclization Reactions of cyclohexadienes derived from sequential additions to (arene)(tricarbonyl)chromium complexes. Preliminary communication
Authors: Beruben Dov , Kündig E. Peter 
Published: December 2004

AbstractCyclohexa‐1,3‐dienes 7–10 with a 1,5,6‐substitution pattern were prepared in a one‐pot reaction sequence by sequential addition of MeLi and propargyl bromides to the tricarbonylchromium complex 1a. These products were subjected to radical cyclization procedures. Vinyl radical generation by Bu3Sn addition to the propargyl group in 7–10 was followed by regio‐ and diastereoselective intramolecular ring closure. Two different 5‐exo‐trig cyclizations are possible via different vinyl radical intermediates and cyclization to one or the other of the termini of the cyclohexadiene moiety. Internal alkynes reacted to yield exclusively the cis‐fused hexahydroindene products 12–14, whereas the terminal alkyne yielded bicyclo[3.2.1]octenes 11 as sole products.
Determination of the Configuration of Wine Lactone
Authors: Guth Helmut 
Published: December 2004

AbstractThe intense sweet and coconut‐like smelling odorant 1, named ‘wine lactone’, was isolated from different wine varieties. The chemical structure of this compound, which has not yet been detected in wine or a food, was identified by high‐resolution mass spectrometry (HR‐MS) as 3a,4,5,7a‐tetrahydro‐3,6‐dimethylbenzofuran‐2(3H)‐one. For the evaluation of the configuration of wine lactone, stereochemically controlled syntheses were developed. All eight isomers were characterized by NMR, MS, IR, and CD measurements. The configuration of ‘wine lactone’ was in agreement with synthesized (3S,3aS,7aR)‐enantiomer (1a) on the basis of enantioselective GC. For this isomer, the lowest odor threshold (0.02 pg/1 air) was detected.
The Addition of tert‐Butyl (Me3Ċ) and (tert‐Butoxy)carbonylmethyl (Me3CO2CĊH2) radicals to alkynes in solution studied by ESR spectroscopy
Authors: Rubin Herbert , Fischer Hanns 
Published: December 2004

AbstractAbsolute rate constants and their temperature dependence are determined by time‐resolved electron spin resonance for the addition of Me3Ċ to 20 and of Me3CO2CĊH2 to six mono‐ and disubstituted alkynes in solution. For Me3Ċ the rate constants show polar alkyne‐substituent effects which are, however, weaker than for the corresponding alkenes. For Me3CO2ĊH2, the rate constants do not vary strongly with alkyne substitution and probably increase with increasing reaction exothermicity. Both radicals react generally slower with alkynes than with alkenes which is discussed in terms of the state correlations. Several vinyl‐type radical adducts of Me3Ċ to alkenes are characterized by electron spin resonance, and their spectral data indicate linear or bent configurations of the radical carbon depending on the substitution.
Ionization and Partitioning Profiles of Zwitterions: The case of the anti‐inflammatory drug azapropazone
Authors: Caron Giulia , Pagliara Alessandra , Gaillard Patrick , Carrupt Pierre‐Alain , Testa Bernard 
Published: December 2004

AbstractAzapropazone (1) is a non‐steroidal anti‐inflammatory drug (NSAID) whose chemical structure is markedly different from that of other agents in this class and challenges our understanding of structure‐activity and structure‐permeation relationships. Using a variety of experimental and computational techniques, we studied 1 for its molecular structure in the gas phase and non‐protic polar solvents, protonation/deprotonation equilibra, tautomerism, and pH‐lipophilicity profiles (octan‐1‐ol/H2O and dodecane/H2O). Other NSAIDs and model compounds were also examined for comparison. Due to its very low acidic pKa1, 1 exists in the physiological pH range as a zwitterion and as an anion. Some pharmacological implications of these findings are discussed.
The Degradation Mechanism of an Oral Cephalosporin: Cefaclor
Authors: Vilanova Bartolomê , Donoso Josefa , Muñoz Francisco , García‐Blanco Francisco 
Published: December 2004

AbstractThe degradation of cefaclor (1), an oral cephalosporin antibiotic, was studied at 37° in a neutral aqueous medium by HPLC and 1H‐NMR. Under these conditions, 1 underwent intramolecular aminolysis by the 7‐side‐chain NH2 group on the β‐lactam moiety to give a piperazine‐2,5‐dione. The most prominent peak in the HPLC profile of a degradation solution from 1 was isolated by prep. HPLC. Mechanistically, the formation of this degradation product cis‐11 from 1 involves the contraction from a six‐membered cephem ring to a five‐membered ring, which presumably takes place via a common episulfonium ion intermediate 9 (see Scheme). Loss of the Cl‐atom from 3‐chloro‐3‐cephem is a general reaction subsequent to β‐lactam ring opening.
Chiral Diselenides from Benzylamines: Catalysts in the Diethylzinc Addition to Aldehydes
Authors: Wirth Thomas , Kulicke Klaus J. , Fragale Gianfranco 
Published: December 2004

AbstractA series of new chiral diselenides with a N‐atom in the side chain was prepared by a short synthetic sequence (Scheme 1). Only 1 mol‐% of these diselenides catalyzed very effectively the diethylzinc addition to various aromatic and α,β‐unsaturated aldehydes yielding the secondary alcohols in up to 98% ee (Scheme 2 and Tables 1 and 2). An asymmetric amplification was observed with these catalysts. Detailed NMR studies were performed to characterize the catalytically active species.
Lipid Masking and Reactivation of Angiotensin Analogues
Authors: Maletínskâ Lenka , Neugebauer Witold , Parê Marie‐Christine , Pêrodin Jacqueline , Pham Dung , Escher Emanuel 
Published: December 2004

AbstractStudies on post‐angioplastic restenosis have shown the implication of angiotensin II (Ang) as a myoproliferative mediator. The antiproliferative efficacy of non‐peptide Ang antagonists on the rat carotid model is of 50%, whereas a continuously infused peptide antagonist at low doses totally blocks neointimal growth. To explore the feasibility of depot forms of Ang that may be introduced during angioplasty and thus prevent restenois, lipid‐masked Ang analogues of the following general structure were prepared: [Xxx°, Yyy1]Ang with Xxx = decanoyl or palmitoyl and Yyy = Ser, Cys, Asp, β‐lactoyl, 3‐mercaptopropanoyl or succinyl. All fatty acylated peptides [Xxx°, Yyy1]Ang were practically inactive, and O‐ or S‐esterified Ser and Cys peptides underwent intramolecular transcylation giving inactive Nx‐acylated peptides. O‐Acylated [β‐mercaptopropanoyl1]Ang were easily hydrolyzed into their biologically active[Yyy1]Ang forms, either by mild saponification or by lipase activity.
A Formal Total Synthesis of (+)‐Methyl Trachyloban‐18‐oate and (+)‐Methyl 16‐Oxo‐17‐norkauran‐18‐oate: Regio‐ and Diastereoselective Preparation of Methyl (13S)‐13‐Hydroxyisoatisiren‐18‐oate from (−)‐Abietic Acid
Authors: Berettoni Marco , De Chiara Giovanna , Iacoangeli Tommaso , Lo Surdo Paola , Bettolo Rinaldo Marini , Di Mirabello Lorenzo Montagnini , Nicolini Luca , Scarpelli Rita 
Published: December 2004

AbstractA novel preparation of methyl (13S)‐13‐hydroxyisoatisiren‐18‐oate (4), a key‐intermediate in a synthesis of (+)‐methyl trachyloban‐18‐oate ((+)‐1), from (−)‐abietic acid, is described. Since (−)‐1 has been previously converted into (−)‐methyl 16‐oxo‐17‐norkauran‐18‐oate ((−)‐16), our preparation of 4 constitutes also a formal total synthesis, from (−)‐abietic acid, of (+)‐16. Key steps in this approach were the allene photoaddition to podocarp‐8(14)‐en‐13‐one (5) and the conversion of the endo‐toluene‐4‐sulfonate 11 into the exo‐benzoate 12b.
Synthesis of 1,2,5‐Thiadiazepine Derivatives by Ring Enlargement of 1,2‐Thiazetidin‐3‐one 1,1‐Dioxides with 3‐Amino‐2H‐azirines
Authors: Mihova Tonya R. , Linden Anthony , Heimgartner Heinz 
Published: December 2004

AbstractAt 0° in MeCN, 2,2‐disubstituted 3‐amino‐2H‐azirines 1 and 4,4‐disubstituted 1,2‐thiazetidin‐3‐one 1,1‐dioxides 7 react smoothly to give 1,2,5‐thiadiazepin‐6‐one 1,1‐dioxides of type 8 (Scheme 2). The reaction mechanism of this regiospecific ring enlargement to seven‐membered heterocycles follows previously described pathways. The structures of 7a and 8b were established by X‐ray crystallography (see Figs. 1 and 2).
From Inactive Nortopsentin D, a Novel Bis(indole) Alkaloid Isolated from the Axinellid Sponge Dragmacidon sp. from Deep Waters South of New Caledonia, to a Strongly Cytotoxic Derivative
Authors: Mancini Ines , Guella Graziano , Pietra Francesco , Debitus Cécile , Waikedre Jean 
Published: December 2004

AbstractNortopsentin D (5), a bis(indole) alkaloid unique for bearing a 2‐amino‐methylimidazole appendage at the central 1H‐imidazol‐5(4H)‐one nucleus, was isolated in abundance, besides the putative biogenetic precursor 6 of its appendage, from the deep‐water axinellid sponge Dragmacidon sp. Structural elucidation of 5 by NMR and MS methods heavily relied on its N‐methyl derivatives 8–11. Unusually for topsentin‐type structures, natural 5 and semisynthetic methyl derivatives 8 and 10 proved inactive on KB tumoural cells, while introduction of the last three methyl groups, amazingly led to highly cytotoxic 11.
Synthesis of Enantiomerically Pure Carbohydrate‐Derived Annulated Cyclopentadienes and Ferrocenes
Authors: Li Zhi , Vasella Andrea 
Published: December 2004

AbstractThe cyclopentadienes 3a/b/c, 8b/c, 12a/b/d, and 16a/b/d were prepared as mixtures of regioisomers from the D‐mannitol‐derivatives 1,6,10, and 14 and transformed into the ferrocenes 17, 18, and 19 (73%; 38:17:45), 23, 24, and 25 (70%; 6:42 :52), 26 (31%), and 27 (27%), respectively. Deprotection of 17–19 with HCl/MeOH gave the H2O‐soluble ferrocenes 20–22; chloromercuration and iodination of 17 via 29 led to the C2‐symmetric diiodo‐ferrocene 30. The mono(chloromercurio) derivative 28, obtained as a by‐product, was also transformed into 29. The structure of the ferrocenes 18 and 19, and of the bis(chloromercurio)ferrocene 29 has been established by X‐ray analysis. The starting cyclopentadienes 3 were obtained in 50% yield from 1 by dialkylation of CpNa, followed by thermolysis of the spiro‐annulated 2. Similarly, dimesylate 6 (from 4) gave the spiro‐annulated diene 7 and the annulated dienes 8 in about equal amounts; thermolysis transformed 7 into 8 (62%). The dienes 12 were prepared in 15% yield from the ditriflate 10 via 11, the dimesylate 9 proving insufficiently reactive, and the dienes 16 (49%) from 14 via 15.
Multiple Adducts of C60 by Tether‐Directed Remote Functionalization and synthesis of soluble derivatives of new carbon allotropes Cn(60+5)
Authors: Isaacs Lyle , Diederich François , Haldimann Richard F. 
Published: December 2004

AbstractA comprehensive series of multiple adducts of C60 was prepared by tether‐directed remote functionalization. When the tether‐reactive‐group conjugates 2 and 10 were attached to methano[60]fullerenecarboxylic acid ( = cyclopropafullerene‐C60‐Ih‐carboxylic acid) and C60, respectively, the e‐bis‐adducts 4 and 9 (Schemes 1 and 2) were obtained with complete regioselectivity as predicted by semi‐empirical PM3 calculations (Fig. 2). Attachment of the anchor‐tether‐reactive‐group conjugate 13 to C60 by Bingel reaction, followed by double intramolecular Diels‐Alder cycloaddition afforded the tris‐adduct 12 (Scheme 3). Starting from 12, a series of selective e‐additions led to the tetrakis‐adducts 16 and 19 (Scheme 4), pentakis‐adducts 20–23 (Scheme 5), and, ultimately, to hexakis‐adducts 24 and 25 (Scheme 6), and 29 and 30 (Scheme 7) with a pseudo‐octahedral addition pattern on the fullerene core. Oxidative cyclization of diethynylmethanofullerene 30 under Eglinton‐Glaser conditions afforded the trimeric and tetrameric acetylenic macrocycles 26, with three, and 27, with four appended C60 moieties, respectively (Scheme 8). These multinanometer‐sized compounds are the first soluble derivatives of C195 and C260, two members of a new class of fullerene‐acetylene hybrid C‐allotropes with the general formula Cn(60 + 5). The matrix‐assisted laser‐desorption time‐of‐flight mass spectra of 26 and 27 showed a remarkable fragmentation; the sequential loss of fullerene spheres led to the formation of ions corresponding to mono‐fullerene adducts of the cyclocarbons cyclo‐C15 and cyclo‐C20 (Fig. 4). Large solvent effects were observed in the Bingel addition of 2‐bromomalonates to higher adducts of C60, with the use of polar solvents enhancing the reaction rate without loss of regioselectivity. Experimental evidence for the enhanced reactivity of eface over eedge bonds was obtained, which had previously been predicted in computational studies. The correlated series of mono‐ to hexakis‐adducts of C60 allowed identification of the changes in reactivity and physical properties that occur, when the conjugated π‐electron chromophore of the fullerene is reduced as a result of increasing functionalization; this analysis is the subject of the directly following paper.
Steroidal, Aldosterone Antagonists: Increased selectivity of 9α,11‐epoxy derivatives
Authors: Grob Jürgen , Boillaz Michel , Schmidlin Julius , Wehrli Hansuli , Wieland Peter , Fuhrer Hermann , Rihs Grety , Joss Urs , Gasparo Marc De , Haenni Henry , Ramjoué Hans Peter , Whitebread Steven E. , Kalvoda Jaroslav 
Published: December 2004

AbstractIn the search for aldosterone antagonists with an optimal activity profile, twelve 9α, 11‐epoxy‐steroids were prepared and compared with their 9α, 11α ‐unsubstituted analogues in terms of steroid receptor binding in vitro and electrolyte excretion in vivo. Substitution of the parent structures by an epoxy group at positions 9α, 11 resulted in marginal effects on mineralocorticoid receptor binding and electrolyte excretion, but greatly reduced androgen and gestagen receptor binding. This finding is reflected in the largely lacking unwanted anti‐androgenic and gestagenic side effects in animal models of the three most interesting 9α, 11 ‐epoxy‐spirolactones 4(CGP 33033), 18(CGP 29245), and 25 (CGP 30083).
Study of the Alkaline Hydrolysis of the Azetidin‐2‐one Ring by ab initio Methods: Influence of the solvent
Authors: Frau Juan , Donoso Josefa , Muñoz Francisco , Vilanova Bartolomé , García‐Blanco Francisco 
Published: December 2004

AbstractA comprehensive study of the alkaline hydrolysis of the β‐lactam ring of azetidin‐2‐one was carried out using ab initio molecular‐orbital calculations at the RHF/6‐31 + G* level. The influence of the solvent on this reaction was investigated by using the reaction field method (SCRF); the solvent was found to suppress the interference of some gas‐phase reactions and allow the presence of a transition state to be detected as the nucleophile approaches the β‐lactam ring. The transition state corresponds to a structure where the OH− group lies at a distance of 1.927 Å from the CO group of the β‐lactam ring and exhibits a potential barrier of 13.6 kcal/mol.