bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies in organic mass spectrometry—X: The fragmentation of substituted 1,3‐cyclo‐pentanediones and 1,2,4‐cyclopentanetriones, related to hop bitter acids
Authors: Cant E. , Vandewalle M. 
Published: May 2005

AbstractThe Mass spectra of some 1,3‐cyclopentanediones and 1,2,4‐cyclopentanetriones, related to compounds encountered in the chemistry of hops bitter constituents have been determined. Methyl substituted compounds mostly show ring degradation, while for longer alkyl groups and acyl groups, fragmentations in the side chain carry most of the total ionization. When both alkyl (> 2C) and acyl substituents are present, fragmentations in the alkyl group always occur before those in the acyl side chain. The observed degradation processes are useful for the interpretation of the spectra of hop bitter acids and derived products.
Etude d'un Couple de Diastereoisomeres en Spectrometrie de Masse: Les 2,3‐Diphenyl‐butanes Thréo et Erythro
Authors: Pechine J. M. 
Published: May 2005

AbstractLes spectres de masse de 2,3‐diphénylbutanes érythro et thréo sont attribués à un réarrangement et à une rupture simple; leur calcul est proposé. II est suggéré que les différences entre les spectres des deux isoméres proviennent essentiellement de al différence d'enthalpie entre les ions moléculaires et non de la différence d'enthalpie entre les états de transition du réarrangement; il en est déduit qu'à l'état gazeux le 2,3‐diphénylbutane thréo est plus stable que l'érythro.
Elektronenstossinduzierte Fragmentierung von Trimethyl‐Benzaldehyden
Authors: Schwarz Helmut , Bohlmann Ferdinand 
Published: May 2005

AbstractDas ungewöhnliche Fragmentierungsverhalten von Trimethylbenzaldehyden wurde durch 2H‐ und 13C‐markkierte Verbindungen aufgeklärt. Statistischen Berechnungen Zeigen, dass in diesem Fall die C‐Atome nicht gleichwertig sind, es für die H‐Atome bezüglich der C2H4‐Eliminierung beobachtet wird.
Specific and random fragmentations in the mass spectra of some neopentyl compounds
Authors: Holmes J. L. , Tong D. C. M. , Rye R. T. B. 
Published: May 2005

AbstractThe mass spectra of neopentyl alcohol, bromide and chloride and some 13C and 2H labelled analogues have been studied. Most fragmentations of the molecular ions of these compounds occur by simple bond cleavages and do not involve rearrangement before fragmentation. We propose that in the [M  CH3]+ fragment ions, seven of the eight hydrogen atoms and all four carbon atoms are involved in randomisation when an ethylene molecule is ejected. The eighth hydrogen atom (which comes from a methyl group) is probably associated with the heteroatom. The neopentylcation, observed only in the mass spectrum of the bromide, fragments mainly by loss of an ethylene molecule, also containing randomly selected hydrogen and carbon atoms. The [C4H7]+ ion also was observed to undergo complete atom scrambling.
Chemical ionization mass spectrometry using ammonia reagent gas. Selective protonation of conjugated ketones
Authors: Dzidic I. , McCloskey James A. 
Published: May 2005

AbstractStudies using ammonia as a selective reagent gas in chemical ionization mass spectrometry were extended to conjugated ketones. Their proton affinities were in the range of most nitrogen‐containing compounds (> 207 ± 3 kcal/mole), thereby permitting proton transfer from [NH4]+‐, leading to well stabilized protonated molecular ions as the most abundant ion products.
Factors influencing the formation of some characteristic fragment ions in the mass spectra of 16‐trimethylsilyloxy androstanes
Authors: Vouros Paul , Harvey D. J. 
Published: May 2005

AbstractThe mass spectra of the trimethylsilyl derivatives of several steroids containing a 16‐hydroxy function are presented. The mechanisms giving rise to various characteristic fragment ions were investigated with the aid of deuterium and 18O‐labeling.
Energetic data as a guide to the interpretation of mass spectral features of dicarbonyl diketonates of Rh and Ir
Authors: Bonati F. , Distefano G. , Pignataro S. , Torroni S. 
Published: May 2005

AbstractThe relative intensities and appearance potentials of the principal ions formed from a series of rhodium and iridium dicarbonyl diketonates were measured by mass spectrometry. These compounds show the usual CO losses generally found in the fragmentation of metal carbonyls. Additionally several fragmentation peculiarities characteristic of metal acetylacetonates were found. Energetic data were used to interpret some aspects of the cracking patterns.
Etude de la fragmentation de semi‐carbazones terpeniques
Authors: Cassan J. , Azarro M. , Reed R. I. 
Published: May 2005

AbstractDans le cadre d'une étude générale des dérivés des carbonylés des terpénes, nous étudions dans le présent travail, une série de semicarbazones terpéniques en spectrométrie de masse à l'aide de la haute résolution. Nous comparons en fonction des différents squelettes hydrocarbonés, les fragmentations induites par le groupement fonctionnel semicarbazone. Les spectres de masse sont beaucoup plus complexes que ceux des oximes, methyloximes, hydrazones correspondantes. Nous nous sommes basés sur des mécanismes classiques pour rendre compte de la quasi‐totalité des pics obtenus. Nous avons constaté que la fragmentation du squelette des semicarbazones a une importance moins grande que celle des oximes. Le groupement fonctionnel semicarbazone se décompose suivant différentes voies. Les ions obtenus sont à l'origine de dégradations secondaires. Malgré la prépondérance de la localisations de la charge sur l'azote imino, les autres centres jouent un rôle dans la dégradation de ces dérivés terpéniques.
Mass spectral studies of some fructose containing oligosaccharide permethyl ethers
Authors: Das K. G. , Thayumanavan B. 
Published: May 2005

AbstractMass spectrometry can be used to characterise fructofuranose units connected via C2 to another sugar. The intensity of the m/e 101 and m/e 88 ions cannot be used to differentiate between furanose and pyranose ring forms in disaccharide permethyl ethers. The type of glycosidic linkage has considerable influence on the formation of these ions.
Electron‐impact studies—LXXIV: A survey of rearrangement processes in the ‘doubly‐charged ion’ mass spectra of aromatic compounds
Authors: Blumenthal T. , Bowie J. H. 
Published: May 2005

AbstractThe technique of Beynon2 has been used to determine the ‘doubly‐charged ion’ mass spectra of a variety of aromatic compounds which contain pronounced rearrangement peaks in their conventional mass spectra. Many, but not all, of the ‘doubly‐charged ion’ spectra contain similar rearrangement peaks to those observed in conventional spectra.
Specific isotopic labeling of sugars: Applications in mass‐spectral analysis. The mass spectrum of 1,6‐anhydro‐2,3‐O‐iso‐Propylidene‐β‐D‐talopyranose
Authors: Horton Derek , Just Ernst K. , Wander Joseph D. 
Published: May 2005

AbstractDerivatives of 1,6‐anhydro‐2,3‐O‐isopropylidene‐β‐D‐talopyranose (I) specifically deuterated at C‐3 (II), at C‐4 (III), at C‐3 and C‐4 (IV), and in the isopropylidene group (V) have been examined by high‐resolution, electron‐impact mass spectrometry. From the elemental compositions of the fragment ions, the mass‐number shifts upon deuterium incorporation, and analysis of metastable transitions, it was possible to identify the origin of the hydrogen atoms in all fragments formed from I and to present a complete scheme of fragmentation pathways undergone by this molecule.
Fragmentation du 1,2,4‐triazole sous L'impact electronique
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. 
Published: May 2005

AbstractCe travail décrit le comportement sous l'impact életronique du 1,2,4‐triazole et de 1,2,4‐triazole et de quelques dérivés substitués. Les résultats obtenus à l'aide de dérivés deutériés démontrent: 1. L' absence de scrambling (NH‐CH) avant la dégradation. 2. La spécificité du clivage principal (élimination de HCN ou RCN au départ de l'ion moléculaire). 3. La présence en phase gazeuse des deux tautoméres non‐symétriques. La possibilité d'une isomérisation rapide de l'ion moléculaire avant dégradation est également envisagée.
Spectres de masse de derives de l'aza‐6 bicyclo[3, 2, 1]octane
Authors: Furstoss R. , Heumann A. , Waegell B. , Gore J. 
Published: May 2005

AbstractLes spectres de masse d'une série de dérivés aza‐bicycliques pontés sont examinés Dans la totalité des cas, la fragmentation est à la fois simple et caractéristique. De plus, sur deux couples d'épimères, on observe un effet stéréochimique, se traduisant par des fragmentations nettement différenciées.
Spectrometrie de Masse du Dimethoxy‐2,6 Naphtalene et de Certains de ses Derives
Authors: Castonguay J. , Rossi A. , Richer J. C. , Rousseau Y. 
Published: May 2005

AbstractOn rapporte les spectres de masse du diméthoxy‐2,6 naphtaléne et de 14 de ses dérivés. La rationalisation du mode de decomposition par impact électronique qui est proposée, est confirmée la plupart du temps par des pics dûs aux transitions métastables appropriées. L'ion moléculaire, qui est le plus intense des ions dans chacun des spectres enregistrés ne semble pas subir d'élimination directe d'un group méthoxy ou de tout autre substituant directement relié au noyau naphtalénique. La dégradation semble plutot amorcée par l'élimination d'un radical méthyle à partir de l'ion moléculaire. Pour les dérivés nitrés, on a pu mettre en évidence la perte d'une molécule d'oxyde nitrique de l'ion moléculaire. Ce processus est confirmé par une mesure précise de masse du fragment résultant.
The mass spectra of some 2,1,3‐benzothiadiazoline and 2,1,3‐benzothiadiazine 2,2‐dioxides
Authors: Bancroft K. C. C. , Guindi L. H. Morcos , Temple A. F. , Millard B. J. 
Published: May 2005

AbstractAlthough the behaviour of 1H, 2H‐2,1,3‐benzothiadiazoline 2,2‐dioxide is similar to that of sulphoxides in the mass spectrometer in losing a molecule of SO2, the 1,3‐dimethyl derivative loses the radical SO2H. In addition the radical CH3SO2 is lost in a one step process that must involve a methyl migration. The radical SO2H is also lost from 2,1,3‐benzothiadiazine 2,2‐dioxides methylated in the 3‐position and the hydrogen involved is shown to originate from this methyl group by deuterium labelling. The mass spectra of other 2,1,3‐benzothiadiazine 2,2‐dioxides are also discussed.
Studies in organic mass spectrometry—XII: Mass spectra of chalcones and flavanones. The isomerisation of 2′‐hydroxy‐chalcone and flavanone
Authors: Van De Sande C. , Serum J. W. , Vandewalle M. 
Published: May 2005

AbstractThe mass spectra of isomeric 2′‐hydroxy‐chalcones and flavanones (i.e. 2‐phenyl‐chroman‐4‐ones) are essentially identical. Thermal isomerisation prior to ionisation was ruled out. A study of metastable transitions (first and second field free region of a double focusing instrument), as well as low energy spectra of both isomers, pointed towards completely identical fragmentation pathways for the two compounds. Five deuterated compounds were then investigated. The heats of formation of the most important ions were determined. It was concluded that an intramolecular equilibrium exists between a chalcone type and a flavanone type molecular ion.
Substituent effects in mass spectrometry—II. The effect of substituents on the dissociation of para and meta disubstituted benzenes
Authors: Benoit F. 
Published: May 2005

AbstractThe effect of substituents on the activation energy for primary dissociation processes in the molecular ions of mono‐ and para and meta di‐substituted benzenes has been examined. Where the daughter ion retains the substituent group, variation of the energy of activation derives from a combination of the effects of substituents on the ionisation potential of the molecular ion and the appearance potential of the daughter ion. An equation relating the energy of activation for the fragmentation of the molecular ion of a mono‐substituted benzene to that of related para and meta di‐substituted benzenes is presented.
Alloxazines and isoalloxazines. Mass spectrometric analysis of riboflavin and related compounds
Authors: Brown Peter , Hornbeck Cecil L. , Cronin John R. 
Published: May 2005

AbstractThe positive ion electron‐impact mass spectra of a series of alloxazines, iso‐alloxazines and some derivatives have been examined. The compounds employed were lumichrome (7,8‐dimethylalloxazine), 1,3‐dimethyllumichrome, lumiflavin (7,8,10‐trimethyl‐iso‐alloxazine), 3‐methyllumiflavin, riboflavin [7,8‐dimethyl‐10‐(D‐1′‐ribityl)‐iso‐alloxazine], riboflavin tetraacetate, 3‐methylriboflavin tetraacetate and riboflavin tetrapropionate. By using exact mass measurements, metastable ion defocusing and the mass/composition shifts occurring with derivatives, it has been possible to arrive at detailed interpretations of the mass spectra of all compounds. With lumichrome and lumiflavin, fragmentation commences by elimination of HNCO from the pyrimidine ring. With riboflavin and its derivatives the ribityl chain cleaves off first, followed by decomposition of the iso‐alloxazine ring. Application of these methods and findings to the structural analysis of chemically interesting modified flavins is predicted to be rewarding.
On the mass spectra of thallium(III) porphyrin chelates
Authors: Smith K. M. 
Published: May 2005

AbstractThallium(III) porphyrins show anomalous features in their mass spectra compared with other metalloporphyrins. The base peak in all of the spectra arises by loss of the thallium atom and its axial ligands with transfer of two hydrogens to the macrocycle; the liberated thallium undergoes ion‐molecule interaction with the thallium porphyrin, resulting in the observation of ions containing two thallium atoms per porphyrin ligand.
Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—IV: Mechanistische Betrachtungen zur Bildung des Benztropyliumkations aus den Chlormethyl‐Naphthalinen und 1‐Chlor‐Phenyl‐(5)‐Penten‐(2)‐in‐(4)
Authors: Schwarz Helmut , Bohlmann Ferdinand 
Published: May 2005

AbstractMassenspektrometrische Untersuchungen von 2H‐ und 13C‐markierten Derivaten des 1‐ bzw. 2‐Chlormenthyl‐naphthallins und des 1‐Chlor‐Phenyl‐(5)‐penten‐(2)‐in‐(4)s zeigen, dass das Ion [C11H9]+ das unter Acetylen‐Eliminierung [C9H7]+ ergibt, eine Benztropyliumkationstruktur besitzt. Modellbetrachtungen zeigen, dass die Bildung diese Kations über einen gemeinasmen Übergangszustand mit einem Dreiring sehr wahrscheinlich ist.
Geminale Spaltung Beim Massenspektrometrischen Zerfall von Benzodioxasilolen
Authors: Liehr J. G. , Richter W. J. 
Published: May 2005

AbstractEin stufenweiser Verlust von zwei Substituenten (CHC3/CH3 bzw. H/CH3 Radikale) dessenlben Zentralatoms (silicium), ein ungweöhnlicher Vorfall in der Massenspektrometrischen Fragmentierung, wird für 1,3,2‐Benzodioxasilole berichtet. Da naheliegende Möglichkeiten für Skelettumlagerungen fehlen, wird eine durch die niedrigeren Si‐C und Si‐H Bindungsenergien erleichterte geminale spaltung vorgeschlagen.
The mass spectrometry of some aromatic azides
Authors: Fraser R. T. M. , Paul N. C. , Bagley M. J. 
Published: May 2005

AbstractBromophenyl azides provide the only exceptions to the observation that nitrogen (N2) is eliminated from the molecular ions. Splitting out of HCN, C2H2 and (in the case of acyl or o‐nitroaryl azides) CO are important processes.
Mass spectrometric studies of some 4‐acyl substituted 1‐phenyl‐3‐methyl‐5‐pyrazolones
Authors: Larsen Elfinn , Qureshi Iqbal H. , Møller Jørgen 
Published: May 2005

AbstractThe electron‐impact‐induced fragmentation of 1‐phenyl‐3‐methyl‐5‐pyrazolone and six 4‐acyl substituted derivatives, have been studied with the aid of deuterium labelling, high resolution mass measurements and the metastable defocusing technique. The mass spectra of the pure keto and the pure enol forms do not show any significant differences. The predominant decomposition of the 4‐acyl substituted pyrazolones is the α‐cleavage with respect to the carbonyl group leading to intense peaks at m/e 201 by loss of the alkyl group. In the case of benzoyl and ethoxycarbonyl derivatives the α‐cleavage is associated with a specific hydrogen rearrangement causing the loss of a benzene and an ethyl alcohol molecule, respectively.
Spectrometrie de Masse de Produits Naturels Aromatiques Polychlores
Authors: Butruille Daniel , Dominguez Xorge A. , Teller Gérard 
Published: May 2005

AbstractOn discute les spectres de masse de trois produits naturels aromatiques: le diméthoxy‐1,4 tétrachloro‐2,3,5,6 benzén (I), le méthoxy‐4 tétrachloro‐2,3,5,6 phénol (II) et le diméthoxy‐1,4 nitro‐2 trichloro‐3,5,6 benzéne (III). Les principlaes fragmentations sont expliqués en fonction de la formation de la structure quinoide (a), qui conduit sous l'impact électronique à la formation de l'ion chlorocyclopropénone (c). On propose également des voies secondaires conduisant à la formation d'ions [Cx]+. On relevé les variations introduites dans la fragmentation par la présence du groupement nitro.
Etude de Steroides Fluores par Spectrometrie de Masse—IV. Fluoro‐3 Epoxy‐5,6 Steroides
Authors: Borgna J. L. , Guida A. , Fonzes L. 
Published: May 2005

AbstractL'étude d'époxydes 5,6 de stéroïdes flourés en 3 ne nous a pas permis de mettre en évidence l'influence de l'atome de flour sur la fragmentation. Par contre, nous avons montré que la stéréochimie de l'époxyde joue un rôle prépondérant.
Mass spectrometry of the trimethylsilyl derivatives of some cardiac aglycones and monoglycosides
Authors: Falkner Fred C. , Frölich Jürgen , Watson J. Throck 
Published: May 2005

AbstractMass spectra of the trimethylsilyl (TMS) ethers of digitoxigenin, digoxigenin, digitoxigenin monodigitoxoside, digoxigenin monodigitoxoside and peruvoside were obtained. Ions appearing at m/e 170 and m/e 183 are proposed to be indicative of the enol TMS ether moiety as confirmed by appropriate shifts in the mass spectrum of digitoxigenin derivatized with perdeuterotrimethylsilylating reagent. The TMS ether derivatives of the monoglycosides produced abundant molecular ions and the base peaks in the spectra represent fragments of the sugar portion of the molecule.
The ion kinetic energy spectra of isomeric chlorobenzenes and polychlorinated biphenyls (PCB'S)
Authors: Safe S. , Hutzinger O. , Jamieson W. D. 
Published: May 2005

AbstractThe ion kinetic energy (IKE) spectra of the isomeric di‐and trichlorobenzenes have been examined and the data for the latter compounds suggested that there was incomplete chlorine randomization in their molecular ions in the first field‐free region of the mass spectrometer. Previous studies on the mass spectra and [metastable ion]/[daughter ion] ratios of the di‐, tetra‐ and hexachlorobiphenyls (PCB's) indicated chlorine randomization in the molecular ions of those isomers containing less than two chlorine groups ortho to the Ph‐Ph ring junction. In contrast the IKE spectra of the isomers are different and the results indicate incomplete chlorine randomization in the first field‐free region of the mass spectrometer. These spectral differences may be of some use in PCB analysis.
Multiply charged ions in the mass spectra of aromatics
Authors: Engel Robert , Halpern Donald , Funk Betty‐Anne 
Published: May 2005

AbstractThe prominence of multiply charged molecular and fragment ions upon electron‐impact in the mass spectrometer is proposed as an experimental, empirical indication of aromatic character. The effects of electron withdrawing and donating substituents on the production of multiply charged ions are considered and appearance potentials are noted for several species.
Mesoionic compounds—XIX: Mass spectral fragmentation patterns for some five‐membered systems containing oxygen, nitrogen and sulfur
Authors: Potts K. T. , Armbruster R. , Houghton E. , Kane J. 
Published: May 2005

AbstractMesoionic compounds of the s‐triazole, 1,3,4‐oxadiazole, 1,3,4‐thiadiazole, 1,2,3‐thiadiazole, 1,3‐thiazole and 1,3‐dithiole systems all underwent deep‐seated decomposition on electron‐impact to small stable ions, determined to a large extent by the nature of the peripheral heteroatoms and the exocyclic substituent. In some instances fragmentation most probably involved an open‐chain isomer of the cyclic system.
Heterocyclic studies—XXIX: Mass spectra of some 1,2‐dihydro‐5‐trifluoromethyl‐pyrimido(5,4‐E)AS‐triazines
Authors: Clark Jim 
Published: May 2005

AbstractMass spectra of five 7‐substituted‐1,2‐dihydro‐5‐trifluoromethylpyrimido(5,4‐e)as‐triazine derivatives are recorded. Fragmentation pathways, elucidation of which was assisted by deuterium labelling and accurate mass measurements, are compared with those of corresponding heteroaromatic compounds. Loss of HF initiated the major breakdown pathways, unless a large 7‐substituent was present, which then fragmented preferentially.
Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen—IXSterische Effekte in den Massenspekten der Stereoisomeren von Decalin‐2,3‐diolen, Decalin‐2,4‐Diolen und Ihen Dimethyläthern
Authors: Grützmacher Hans‐Friedrich , Fechner Karl‐Heinz 
Published: May 2005

AbstractDie Massenspektren aller Stereoisomeren des Decalin‐2,3‐diols und des Decalin‐1,4‐diols sowie ihrer Dimethyläther und einiger spezifisch deuterierter Dervae dieser Verbindungen werden diskutiert. Bei den Decallin‐2,3 diolen weden nur geringe quantitative Unterschiede in den Ionenintensitätten gefunden. Die Massenspektren der stereoisomeren 2,3‐Dimethoxy‐decaline sind innerhalb der cis‐ und trans‐Reihe nahezu glech, so daß eine massenspektrometrische Identifizierung der Stereoisomeren schwerfällt. Stereoselektive Eliminierungsreaktionen in den Molek¨︁l‐Ionen können nicht nachgewiesen werden.In den Massenspektren der Decalin‐1,4‐diole treten charakteristische Unterschiede in den Intensitäten der Ionen [M  H2O]+˙ auf, die in übersichtlicher Weise wie bei de Cyclohexan‐1,4‐diolen mit der Molekülgeometrie der einzelnen Stereoisomeren in Beziehung gesetzt werden können. Die sterischen Kontrolle der H2O‐Abspaltung aus den Molekül‐Ionen wird durch Deuterium‐Markierungen bewisen. Die Massenspektren der Stereoisomeren der 1,4‐Dimethoxydecaline zeigen ebenfalls deutliche Unterschiede in den Intensitäten der [M  CH3OH]+˙‐Ionen. Weiterhin treten Peaks von [M  CH2O]+˙‐Ionen nur in den Massenspektren derjenigen Isomeren auf, bei denen in irgendeiner der Moleküklonformationen ein kurzer Abstand zwischen den Methoxygruppen errricht werden kann. Die Stereoseletivität der CH3OH‐ und CH2O‐Eliminierungen wird gleichfalls druch Deuterium‐Markierungen bewiesen.
Substituent effects on retro‐Diels‐Alder reactions in some 3,6‐diphenyl‐5‐aryl‐4‐amino‐Δ′cyclohexenes
Authors: Das K. G. , Madhusudanan K. P. 
Published: May 2005

AbstractThe variation in the ratio of the relative abundances of the diene and ene ions formed by competing retro‐Diels‐Alder reactions with electron energy and subtituents has been studied. This ratio represents the ratio of the rate constants of the processes and depends on the internal energy distribution within the decomposing molecular ions.
Mass spectral studies of stereoisomers: The photoionisation of some substituted cyclohexanols
Authors: Akhtar Zinat M. , Brion C. E. , Hall L. D. 
Published: May 2005

AbstractThe fragmentation of the stereoisomers of 4‐t‐butylcyclohexanol, and 3‐methylcyclohexanol has been studied by photoionisation mass spectrometry at 1216 Å and 584 Å. Deuterium substitution and high resolution mass spectrometry have been used to gain further insight into the fragmentation pathways.
The mass‐spectral fragmentation of bicyclo[3.3.1]nonanes
Authors: Nicoletti R. , Gambacorta A. 
Published: May 2005

AbstractThe mass spectra of twelve bicyclo[3.3.1]nonanes have been recorded. The high number of metastables observed, exact mass measurements of the ions and low ionising voltage spectra, permitted the rationalisation of most of the fragmentation pathways. The 1‐phenyl substituent triggers the major fragmentation in the hydrocarbon, whereas it has minor influence in the oxygenated compounds. Significant differences in the abundance of [M  H2O]+ ions for stereoisomeric alcohols of this series have been observed.