bluuebunny/crossref_metadata_2025_split huggingface dataset:
Totalsynthese optisch aktiver Steroide. XIII. Mitteilung. Synthese von 4,9(11)‐Androstadien‐3,17‐dion
Authors: Eder Ulrich , Sauer Gerhard , Haffer Gregor , Ruppert Jürgen , Wiechert Rudolf , Fürst Andor , Meier Werner 
Published: December 2004

Synthesis of 4,9(11)‐androstadiene‐3,17‐dione.The total synthesis of 4,9(11)‐androstadiene‐3,17‐dione (23) is described starting from (1 S, 7 aS)‐1‐t‐butoxy‐7a‐methyl‐5,6,7,7a‐tetrahydroindan‐5‐one (8) as a CD‐building block. The key step involves alkylation of 8 with 1‐chloro‐7,7‐o‐phenylenedioxy‐octane‐3‐one (14) a novel AB‐synthon to give the diketone 15. 15 is converted to the secosteroid 20 via the diene enol ether 17 using a previously described procedure. Low temperature methylation of 20 affords predominantly the 10β‐methyl compound 21, which is readily transformed into the title dione 23.
A Stereospecific Synthesis of Biotin from an Aromatic Precursor. Preliminary Communication
Authors: Confalone Pat N. , Pizzolato Giacomo , Uskoković Milan R. 
Published: December 2004

AbstractThe total synthesis of the important natural product biotin 1 from the readily available keto diester 3 is described. This approach features the stereospecific hydrogenation of the thiophene intermediate 19 as the key synthetic step.The required differentiation of the diacid functionality of compound 7 is achieved by selective lactam formation with the terminal acid to yield the 8‐membered lactam 8. A modified Curtius reaction then affords the rearranged diurethane 18 through a series of acyl transfers. Finally, a novel conversion of the 3, 4‐diurethane moiety to the imidazolidone portion of biotin is utilized to complete the synthesis.
Neue Verfahren zur Herstellung von 21‐Fluorsteroiden. Über Steroide. 232. Mitteilung
Authors: Wieland Peter 
Published: December 2004

New methods for the preparation of 21‐fluoro‐steroids.21‐Fluoro‐20‐oxosteroids are obtained either by reacting a 21‐diazo‐20‐oxo‐steroid with hydrofluoric acid or by subjecting a 21‐mesyloxy‐20‐oxo‐steroid to reduction with the radical anion derived from lithium and biphenyl, followed by treatment of the resulting enolate with perchloryl fluoride.
Synthesis of the Gastrointestinal Peptide Hormone Secretin by the Repetitive Excess Mixed Anhydride (REMA) Method
Authors: van Zon Arie , Beyerman Hugo Christiaan 
Published: December 2004

AbstractThe REMA method was found to be very suitable for the synthesis of secretin. The procedure was rapid, since on a 0.2 mmol‐scale the rate of one amino acid per day could be attained, and yielded an unambiguous product after simple ion‐exchange chromatography. REMA‐secretin was found to be chemically identical with secretin prepared by fragment condensations and showed a biological activity of 3.4 (2.9–4.3) clinical units/μg, comparable to that of the natural product (4 clinical units/μg). The yield of purified secretin, a heptacosapeptide amide, calculated on the basis of C‐terminal residue, amounted to 5%.
Überführung des (−)‐Tabersonins in ein Indolo[2,3‐b]chinolizin, eine bemerkenswerte molekulare Umwandlung
Authors: Hofheinz Werner , Schönholzer Peter , Bernauer Karl 
Published: December 2004

The conversion of (−)‐tabersonine into an indolo[2,3‐b] quinolizine, a remarkable molecular transformation.Silver ion assisted solvolysis of the (−)‐tabersonine derivative 6 yields the indolo[2,3‐b]quinolizine 12 by a unique fragmentation/rearrangement sequence. The structure of 12 was determined by spectroscopic methods and has been confirmed by X‐ray crystallography.
Eine Synthese von Bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐on und seinem 14‐Methylderivat
Authors: Karpf Martin , Dreiding André S. 
Published: December 2004

A Synthesis of Bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one and its 14‐Methyl Derivative.A new route to bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one (2) and its 14‐methyl derivative 3 – useful intermediates in the synthesis of cyclopentadecanone (4 = exaltone®) and rac‐muscone (5) – is described.
23Na‐NMR. Linewidths in Binary Mixtures of Oxygenated Solvents
Authors: Detellier Christian , Laszlo Pierre 
Published: December 2004

AbstractThe inference of single bicyclic intermediates in the competition of diglyme (or triglyme)For abbreviations see the table of [1].
with tetrahydrofurfuryl alcohol is confirmed by analysis of the linewidths. The dissymetric bicyclic species are characterized by linewidths increased markedly with respect to the pure solvents, without an accompanying change in the 23Na chemical shift. Conversely, the competition of glyme with the same alcohol involves three equi‐probable intermediates; that of tetrahydrofuran (or tetrahydropyran) is of greater conceptual complexity.
The Oxa‐di‐π‐methane Rearrangement of 1‐Phenyl‐3‐acetylcyclopentene: Identification of the Reactive Triplet as the Localized Styrene π, π*‐State. Preliminary Communication
Authors: Tegmo‐Larsson Inga‐Mai , Gonzenbach Hans‐Ulrich , Schaffner Kurt 
Published: December 2004

Abstract1‐Phenyl‐3‐acetylcyclopenteneIUPAC‐Nomenclature for 3: (3‐phenyl‐cyclopent‐2‐enyl)‐ethanone or methyl (3‐phenylcyclopent‐2‐enyl) ketone.
(3) undergoes triplet‐sensitized oxa‐di‐π‐methane rearrangement to a ca. 3:1 mixture of endo‐ and exo‐1‐phenyl‐5‐acetylbicyclo[2.1.0]pentaneIUPAC‐Nomenclature for 4: endo‐ or exo‐(4‐phenyl‐bicyclo[2.1.0]pent‐5‐yl)‐ethanone.
(4). The reactive triplet of 3 has been identified as the localized styrene π, π*‐state of ET = 59 kcal/mol by comparison of its phosphorescence at 77 K in a rigid glass with that of 1‐phenylcyclopentene, and by sensitization quantum yields at room temperature in liquid solution. These quantum yields are independent of sensitizer energy in the range of 61–74 kcal/mol and reach zero for product formation with a sensitizer of ET = 59 kcal/mol. Although S1 → T1 intersystem crossing is appreciable under phosphorescence conditions (Φp = 0.05), direct irradiation of 3 at 20° does not lead to triplet rearrangement, and the typical singlet 1,3‐acetyl shift to 3‐acetyl‐3‐phenylcyclopenteneIUPAC‐Nomenclature for 8: (1‐phenyl‐cyclopent‐2‐enyl)‐ethanone.
(8) is observed only.
Structure of 1‐exo‐Phenylbicyclo[2.1.0]pentane‐5‐carboxylic acid by X‐Ray Analysis
Authors: Bernardinelli Gérald , Combremont Jean‐Jacques , Gerdil Raymond 
Published: December 2004

AbstractThe title compound (C12H12O2) crystallizes in the monoclinic space group P21/c. The structure was solved by direct methods, and the positions of all the hydrogen atoms were obtained from a difference synthesis. The final Rω was 0.04. Current MO theories of the interaction of unsaturated groups with small ring systems are consistent with the bond length variations encountered in the present substituted bicyclo[2.1.0]pentane skeleton with respect to the unsubstituted hydrocarbon.
Synthesis of Abscisic Acid
Authors: Mayer Hans J. , Rigassi Norbert , Schwieter Ulrich , Weedon Basil C. L. 
Published: December 2004

AbstractA stereoselective synthesis of (±)‐abscisic acid (7) is described in which 2‐cis 3‐methylpent‐2‐en‐4‐yn‐1‐ol (2) is used to introduce the 2‐cis, 4‐trans geometry.
Dediazoniation of arenediazonium ions in homogeneous solution. Part VIII. Reaction kinetics and products in dimethyl sulfoxide
Authors: Hirose Yoji , Wahl George H. , Zollinger Heinrich 
Published: December 2004

Abstractp‐Nitrobenzenediazonium tetrafluoroborate dissolved in dimethylsulfoxide (DMSO) at 50° forms p‐nitrophenol in 88–90% yield. The phenolic oxygen atom originates exclusively from the oxygen atom of DMSO as demonstrated by the use of 18O‐labelled DMSO. The first‐order rate of dediazoniation is the same under N2 as it is in the presence of air. The rate is little influenced by the addition of benzene or iodobenzene. However, the products formed in the presence of these additives are significantly different. UV. spectra and the reactivity of diazonium salt solutions in DMSO when mixed with reagents in aqueous solution demonstrate that a relatively stable charge‐transfer complex is formed between the diazonium ion and DMSO. The product analyses and the kinetic and spectral results of dediazoniation in DMSO with and without additives are consistent with a mechanism in which the rate‐limiting step is the formation of a p‐nitrophenyl radical from the charge‐transfer complex. p‐Nitrophenol and the products with benzene and iodobenzene are formed in subsequent fast competition steps. In the presence of small amounts of pyridine the dediazoniation is much faster and follows a different kinetic law. Pyridine effectively competes with DMSO in the reaction with diazonium ions.
Über die Bildung cyclischer Ionen und bicylischer Übergangszustände beim Zerfall substituierter α,ω‐Alkandiamine im Massenspektrometer. 23. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen
Authors: Schöpp Emanuel , Hesse Manfred 
Published: December 2004

Formation of cyclic ions and bicyclic transition states in the mass spectral decomposition of substituted α,ω‐alkanediamines.N‐Phenethyl‐N(4‐acetamidobutyl)‐p‐toluene‐sulfonamide (4) and its homologues were synthesized and the mass spectral behaviour investigated. After loss of a benzyl radical from the molecular ion two different fragmentation reactions are observed. The lower homologous members – namely compounds 1, 2 and 3 – lose ketene by formation of cyclic ions (Scheme 1). The higher homologues of this series of compounds (4, 5, 6) show a pronounced (to 18% ∑50) loss of p‐toluene sulfonic acid. This decomposition reaction proceeds presumably through a bicyclic transition state (Scheme 3).
Arbeiten über Phosphorsäure‐ und Thiophosphorsäureester mit einem heterocyclischen Substituenten. 10. und letzte Mitteilung. Aza‐Analogie II: Derivate von Oxazolo[4,5‐b]pyridin‐2(3H)‐on, einem Aza‐Analogen von Benzoxazol‐2(3H)‐on
Authors: Rüfenacht Kurt , Kristinsson Haukur , Mattern Günter 
Published: December 2004

Investigations on phosphoric acid and thiophosphoric acid esters with a heterocyclic substituent, 10th and last communication. Aza‐analogy II: Derivatives of oxazolo[4,5‐b]‐pyridin‐2(3H)‐one, an aza‐analogue of benzoxazol‐2(3H)‐one.Oxazolo‐[4,5–b]pyridin‐2(3H)‐one (4), one of the possible aza‐analogues of benzoxazol‐2(3H)‐one (3), is readily prepared starting from furfural (8), using the Clauson‐Kaas transformation (oxydative transformation of furans to pyridines with simultaneous incorporation of a nitrogen atom) and proceeding either (1) via furfurylamine (9), 3‐hydroxy‐pyridine (10), 2‐nitro‐ and 2‐amino‐3‐hydroxy‐pyridine (11) followed by ring closure with phosgene or, on shorter routes, directly (2) via 2‐amino‐3‐hydroxy‐pyridine (11) or (3) via ∝‐methylamino‐(fur‐2‐yl)‐acetic acid amide (12) and 3‐hydroxypicolinic acid amide (13) followed by a Hofmann degradation. Halogenation and nitration of 4 lead to the 6‐substituted derivatives 15–17.A series of thiophosphoric and thiophosphonic acid esters 22–24 with high insecticidal, acaricidal and anthelminthic activities and with extremely low mammalian toxicities up to > 5000 mg/kg (rat p.o.) has been disclosed via the N‐hydroxymethyl and N‐chloromethyl‐derivatives 21 of the oxazolopyridin‐ones 4, 15, 16 and 17 and the thione 14. These esters are aza‐analogues of the known benzoxazolone‐insecticide type 1 and present really divergent properties.The vinyl compounds 25 are easily accessible from the oxazolopyridin‐ones with vinyl acetate. Addition of halogen to form the 3‐(1,2‐dihaloethyl)‐derivatives 26, however, occasionally is troublesome: 3‐(2‐halovinyl)‐derivatives 27 formed as inherent by‐products by dehydrohalogenation handicap further reactions. Some thiophosphoric acid esters 28 and 29 derived from the vinyl compounds 25 and the dihaloethyl compounds 26 resp. are active pesticides too, but their mammalian toxicity ranges from 20–200 mg/kg (rat p.o.), values generally regular in the phosphoric ester field.The one‐step condensation of a hetercyclic NH‐compound, formaldehyde and a thiophosphoric compound (Stäubli procedure) is not applicable to the preparation of the esters 22 because the acidity of the oxazolopyridin‐ones (e.g. 4 and 15) is too high to fulfill the basic requirements of this procedure. An alternative procedure running via the Mannich compounds 31 and 32 fails due to salt formation between Mannich base and thiophosphoric acid.Ring‐homologues such as the benzoxazinone derivatives 37 and the pyrido‐oxazinone derivatives 40 are not pesticidal.The isomeric oxazolo[4,5–c]pyridin‐2‐(3H)‐one (5) and oxazolo[5,4–b]pyridin‐2(3H)‐one (7) could not be prepared.
Identification and Synthesis of two New Organic Sulfur Compounds from the Yellow Passion Fruit (Passiflora edulis f. flavicarpa)
Authors: Winter Max , Furrer Anton , Willhalm Bruno , Thommen Walter 
Published: December 2004

Abstract3‐Methylthio‐hexanol (3) and a mixture of cis‐ and trans‐2‐methyl‐4‐propyl‐1, 3‐oxathiane (6a and 6b) have been identified in a flavor concentrate of the yellow passion fruit of Hawaiian origin. Syntheses of these new flavor constituents are described.
Inhaltsstoffe des Verbenaöls. 1. Mitteilung. Natürliches Vorkommen der Photocitrale und einiger ihrer Derivate
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

Natural Occurrence of Photocitrals and some of their Derivatives (Constituents of Verbena Oil, 1st communication).The analysis of natural verbena oil of authentic origin has revealed the presence of the synthetically known photocitral isomers 2a, 2b, 3 and 6. They are accompanied by 2,5‐dimethyl‐2‐vinyl‐4‐hexenal (7), several oxides 8–12 and some other constituents well known to occur in nature. A new sesquiterpene ether will be discussed in the following publication.The corresponding reduced compounds 15a, 15b and 16 of the photocitral isomers are also present in the essential oil.
Steric Effects in the Reduction of Ketones with Sodium Borohydride
Authors: Müller Paul , Perlberger Jean‐Claude 
Published: December 2004

AbstractThe rates for the reduction of ketones with sodium borohydride are interpreted in terms of two parameters, both derived from force‐field calculations; i.e. the strain difference between alcohol and ketone (Δ strain) and the steric hindrance towards approach of the hydride R. Models for the evaluation of R are discussed. With this approach reduction rates over a range of 108 can be rationalized within a factor of 6–10.
Angular‐ and Energy‐Dependence of Band Intensities in the Photoelectron Spectra of Phosphabenzene and Arsabenzene
Authors: Ashe Arthur J. , Burger Fritz , El‐Sheik Maher Y. , Heilbronner Edgar , Maier John P. , Muller Jean‐François 
Published: December 2004

AbstractThe He(II) photoelectron spectra of phosphabenzene 2 and arsabenzene 3 yield additional ionization energies in the region 17 to 20 eV. The relative intensity changes of the first three bands, compared to their relative intensities in the He(I) spectra, provide support for the previously proposed sequence of states ˜X = 2B1, ˜A = 2A2, ˜B = 2A1. This and the angular dependence of the photoelectron band intensities in the spectra of 2 and 3 is in excellent agreement with the theoretical predictions made by von Niessen, Diercksen & Cederbaum [9].
Einfluss intramolekularer Bewegungen auf die Fluoreszenzquantenausbeute
Authors: Calzaferri Gion , Gugger Heinrich , Leutwyler Samuel 
Published: December 2004

Influence of intramolecular movements on the fluorescence quantum yield.The conditions determining the influence of the movements of different parts of molecules on the fluorescence quantum yield are shown. In the following we discuss four types of intramolecular movements that can help attain the desired fluorescent properties. In the case of methinecyanine dyes such intramolecular movements are responsible for the strong dependence of the fluorescence quantum yield on the solvent viscosity we have observed.
Stereospezifische Synthese zweier 9, 11, 12, 13, 13a, 14‐Hexahydrodibenzo[f, h]pyrrolo[1, 2‐b]isochinoline
Authors: Faber Ludwig , Wiegrebe Wolfgang 
Published: December 2004

Stereospecific Synthesis of two 9,11,12,13,13a,14‐hexahydrodibenzo[f,h]pyrrolo‐[1,2‐b]isoquinolines.The stereospecific synthesis of (13aS)‐(+)‐2,3,6‐ and 3,4,6‐trimethoxy‐9,11,12,13,13a,14‐hexahydrodibenzo[f,h]pyrrolo[1,2‐b]isoquinoline is described. The 2,3,6‐trimethoxy‐compound proved to be the optical antipode of (−)‐antofine, isolated from Cynanchum vincetoxicum L. Pers.
Photoaddition Reactions of 5‐Fluoro‐4,4‐dimethyl‐2‐cyclopentenone
Authors: Thi Giao Vo , Margaretha Paul 
Published: December 2004

AbstractThe photoaddition of 5‐fluoro‐4,4‐dimethyl‐2‐cyclopentenone (4) to 2,3‐dimethyl‐2‐butene leads specifically (in cyclohexane) and selectively (in acetonitrile) to the formation of the oxetanes 16. The title compound is compared in its behaviour to the analogous 6‐fluoro‐4,4‐dimethyl‐2‐cyclohexenone (1) and both α'‐fluoro‐4,4‐dimethyl‐2‐cycloalkenones in turn are compared to the corresponding 2‐cycloalkenones (6 and 3) and 4,4‐dimethyl‐2‐cycloalkenones (5 and 2). The quantum yield for the addition of these enones to 2,3‐dimethyl‐2‐butene and to cyclopentene are discussed.
Intramolecular [2 + 2]‐Photocycloadditions of 6‐Allyl‐2‐cyclohexenones. Formation of Tricyclo[3.3.1.02,7]nonan‐6‐ones and Tricyclo[4.2.1.03,8]nonan‐7‐ones
Authors: Fröstl Wolfgang , Margaretha Paul 
Published: December 2004

AbstractAlkylation of 4,4,6‐trimethyl‐2‐cyclohexenone (1) in toluene in the presence of sodium bis(trimethylsilyl)amide proceeds smoothly to give high yields of compounds 2. Irradiation (λ= 366 nm) of the 6‐allyl‐4,4,6‐trimethyl‐2‐cyclohexenones 2a–c yields mixtures of the isomeric tricyclo‐nonanones 3 and 4, the product ratio depending on the substituent R' of the allylic side chain and on the solvent. The quantum yields for the cyclizations are given.
13C‐NMR. Analysis of the Roxburghines
Authors: Merlini Lucio , Mondelli Rosanna , Nasini Gianluca , Wehrli Felix W. , Hagaman Edward W. , Wenkert Ernest 
Published: December 2004

AbstractThe13C shifts of the alkaloids roxburghine B, C, D and E are determined. They confirm the following configurations for the last three bases: C(18α)‐normal, C(18α)‐pseudoand C(18β)‐pseudo, respectively. Roxburghine B is shown to be a C(18β)‐epi‐alloisomer.
Photolysis of the azo‐precursors of 2,3‐ and 1,8‐naphtoquinodimethane. Preliminary communication
Authors: Gisin Markus , Wirz Jakob 
Published: December 2004

AbstractA novel oxidation method for the synthesis of labile azo‐alkanes is reported. Matrix‐isolated 2,3‐naphthoquinodimethane is obtained by photolysis of 1,4‐dihydrobenzo[g]‐phthalazine in a rigid matrix (EPA glass) at 77 K and the electronic structure of its ground and lowest excited states is discussed. Nitrogen elimination from 1,4‐dihydronaphtho[1,8‐de][1,2]‐diazepine to yield acenaphthene occurs exclusively upon ππ* excitation while irradiation in the n‐π* absorption region induces cis/trans isomerization of the azo‐moiety. Neither ns flash nor low‐temperature photolysis provide evidence for the occurrence of 1,8‐naphthoquinodimethane as an intermediate in the formation of acenaphthene.
The Use of 13C–NMR. Spectroscopy in Biosynthetic Studies. II[1]. Biosynthesis of narasin, a new polyether ionophore from fermentation of Streptomyces aureofaciens [2]
Authors: Dorman Douglas E. , Paschal Jonathan W. , Nakatsukasa Walter M. , Huckstep Lyell L. , Neuss Norbert 
Published: December 2004

AbstractThe labeling of the polyether ionophore, narasin, using 13C‐labeled acetate, propionates, and butyrates in the course of fermentation of Streptomyces aureofacies resulted in the isolation of differently labeled compounds. A careful examination of the 13C‐NMR. spectral data indicated derivation of narasin from five acetate, seven propionate, and three butyrate units. The evidence of indirect incorporation of 13C led to the first documented demonstration of conversion of propionate to butyrate in the course of the synthesis of narasin by S. aureofaciens.
Physical and Chemical Interaction of Homoconjugated Dienes with Tetracyanoethylene
Authors: Haselbach Edwin , Rossi Michel 
Published: December 2004

AbstractEDA‐complexes of bicyclo[2,2,n]alkadienes (n = 1, 2, 3, 4) (1 (n)‐series), 1,4‐cyclohexadiene (2) and various other cyclic monoenes, dienes and trienes as donors and tetracyanoethylene (TCNE) as acceptor were investigated. Spectroscopic and thermodynamic constants of the complexes were determined and correlated with the ionisation potentials (ID) of the hydrocarbon donors obtained from PE. spectroscopy. The nature of the dominant energy contributions to the ground state and the two lowest CT‐states of these weak complexes is discussed and structural conclusions are drawn. The role of the complexes in the addition reaction of the hydrocarbon components and TCNE is discussed. The homo Diels‐Alder addition product of 1 (2) and TCNE, 9,9,10,10‐tetracyanoquadricyclo[2,2,2,02,6,23,5]decane, and the ‘ene’‐addition product of 2 and TCNE, 5‐[1′,1′,2′,2′‐tetracyanoethyl]‐1,3‐cyclohexadiene were prepared and characterized. Preliminary results for the mechanistic scheme governing the dehydrogenation of 2 by TCNE are reported.
The Gas‐Solid Interface The Adsorption of Nitrogen and Neopentane on Synthetic Calcium Carbonates, in relation to microporosity
Authors: Stoeckli Fritz , Sophal Heang , Perret André 
Published: December 2004

AbstractThe adsorption of nitrogen (78 K) and neopentane (253 to 273 K) on two different samples of synthetic calcium carbonate has been used to characterize the state of their surface, with respect to microporosity. The need for well defined standards is revealed by the study of natural Ca/Mg carbonates.
Zur Ermittlung der Konfiguration und Konformation von N‐Glycosyl‐3‐carbamoyl‐pyridinium‐ionen. Eine Berichtigung zu [2]
Authors: Iff Robert , Viscontini Max 
Published: December 2004

Determination and configuration of N‐glycosyl‐3‐carbamoylpyridinium ions. A correction.The work reported twenty years ago by one of us (M. V.) [2] has been reproduced and enlarged. In our previous communication we describe how the kinetics of the periodic oxidation of an anomeric pair of nucleosides would allow to assume the configuration and the conformation of the sugar part of the molecule, but our hypothesis was not confirmed by the 1H‐NMR. spectroscopy. In the present work we show that our point of view was and is definitively exact, but that N‐α‐ and N‐(β‐D‐glucosyl)‐3‐carbamoyl‐pyridinium‐ion have been involuntary confounded in the former publication.
4‐Oxa(thia)‐9‐oxa‐2‐azabicyclo[4.2.1]nonane‐3‐on(thion) derivatives
Authors: Škarić Vinko , Hohnjec Marijan , Škarić Djurdjica 
Published: December 2004

AbstractThe synthesis of 7,8‐dihydroxy‐2‐(2‐methoxycarbonylethyl)‐4,9‐dioxa‐2‐azabicyclo[4.2.1]nonane‐ 3‐thione (16) and of its parents 9‐oxa‐4‐thia‐3‐thione 17, and 9‐oxa‐4‐thia‐3‐one 18 is described. The conversion of 5′‐deoxy‐5′‐iodo‐2′,3′‐O, O‐isopropylidene‐5,6‐dihydrouridin (1) into the 2‐O‐methyl‐5,6‐dihydrouridine 5, the 5′‐O‐acetyl‐5,6‐dihydrouridine 4, and into the N‐(5‐O‐acetyl‐2,3‐O, O‐isopropylidene‐β‐D‐ribofuranosyl)‐N‐(2‐methoxycarbonyl thyl)‐urea (6) invoked 2′,3′‐O, O‐isopropylidene‐2,5′‐anhydro‐5,6‐dihydrouridine (2) as the common intermediate.
Cyclobutanones via the (1‐Oxycyclopropyl)methanol Route
Authors: Wenkert Ernest , Golob Norman F. , Hatch Robert P. , Wenkert David , Pellicciari Roberto 
Published: December 2004

AbstractA variety of alcohols of the 1‐oxycyclopropyl structure, prapared mostly from α‐alkoxy‐α,β‐unsaturated ketnnes and esters by way of reductinn and Simmons‐Smith reaction of the resultant α‐alkoxyallyl alcohols, are shown to rearrange into cyclobutanones on acid treatment (cf. Scheme 1).