Konformationsanalyse, XIV
            <sup>1)</sup>
            Bootkonformationen bei
            <i>tert</i>
            ‐Butylcyclohexan‐Derivaten durch polare 1,3‐diaxiale Wechselwirkungen

Paulsen, Hans; Koebernick, Hubert

doi:10.1002/cber.19761090109

Cited by 7 publications

(2 citation statements)

References 2 publications

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“…1 Erwartungen in der Regel nur eine Abflachung des Sessels an 3C gefunden (Park, Kim & Jeffrey, 1971;Lindberg, 1974;Leung & Marchessault, 1974;Brown & Thiessen, 1969;Foces-Foces, Cano & GarciaBlanco, 1976;Noordik & Jeffrey, 1977). Zwar wurden f'tir Hydrochloride von Aminoderivaten dieser Reihe in L6sung Bootkonformationen festgestellt (Trnka, (~erny, Budeszinsky & Pacak, 1975;Paulsen & Koebernick, 1976), doch konnte bisher in einem dieser F/ille im Kristall ebenfalls nur eine abgeflachte Sesselkonformation vorgefunden werden (Maluszyfiska, Takagi & Jeffrey, 1977). Das Maximum an Einebnung an 3C, das bisher rfntgenographisch festgesteUt wurde, findet sich in Derivaten, in denen der Pyranosering Bestandteil eines weiteren Ringsystems ist, so in der 1,6-Anhydro-3,4-O-isopropyliden-fl-D-talopyranose (Panagiotopoulos, 1974) und der 1,6: 2,3-Dianhydro-fl-D-gulopyranose (Berking & Seeman, 1971), in der der Pyranosering eine Halbsesselkonformation einnimmt.…”

Section: Ringkonformationenunclassified

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

Kopf¹,

Köll²

1978

Acta Crystallogr Sect B

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As pointed out by Larsen & Jerslev, the structure contains a set of open channels parallel to the b axis containing centers of symmetry (0,0,0) and (0,½,0). The minimum distances from the origin inversion center to neighboring atoms are 1.92 A to H(8) and 2.16 A to N(3). 1,4: 3,6-Dianhydro-a-D-glucopyranose, C6HsO4, a pyrolysis product of D-glucose, crystallizes in space group P2,2,2, with a = 6-295 (2), b = 9.002 (4), c = 10.862 (5) A, Z = 4. The tricyclic structure of the title compound was solved by direct methods and refined to a final R w value of 0.05 for 507 independent reflexions. The pyranose ring of the molecule adopts an almost ideal BL4(D ) boat conformation and the furanose ring a distorted envelope conformation, Eo(D ) (phase angle P = 276.8°). References

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Section: Ringkonformationenunclassified

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

Kopf¹,

Köll²

1978

Acta Crystallogr Sect B

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“…The results stI-ongly support and negligible in the comparison 2 4 2 5 (difference of two the correctness of the chair-like6 transition similar stericgaucheeffects). Since thecharge-related and hydrogen bonding effects must be larger in the compari6Paulsen and Koebernick (22) have recently shown for son 20-21 than in 2 4 2 5 it follows from the values given, the ground state that a 1,3-diaxial interaction must be that the ordinary A, Z , and G contributions to the diflarge indeed in order to cause the cyclohexane ring to ferences 20-21 (Fig. 3) the syn-1,3-diaxial arrangement of substituent and nucleophile; however, the size of the interaction remaining would indicate that the deviation is small.…”

Section: Reactionsmentioning

confidence: 99%

The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol

Bovenkamp¹,

Moir²,

Bannard³

1977

Can. J. Chem.

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. Can. J. Chem. 55,4144 (1977).Six related oxiranes (the cis and trans isomers derived from 3-methoxycyclopentene and from 3-methoxvcvclohexene. as well as the oxiranes from the corresuonding unsubstituted olefins) were each treated under the same conditions with an acidic soiution containing charged and uncharged nucleophiles (chloride ion, water, and methanol). The corresponding perchloric acid catalyzed scissions were also carried out. Accurate and reproducible methods of product analysis for the reaction mixtures were developed. In this way, nucleophilic attacks upon different oxiranes were compared directly. Attacks by different nucleophiles upon the same oxirane, or by a single nucleophile upon different positions of the same oxirane, were compared in the very same solution. The results are considered to provide the most extensive demonstration of the effects of charge orientation yet available. The synthesis of some new isomeric 1,2,3-trisubstituted diols and dimethoxyalcohols are reported. Chem. 55,4144 (1977).Six oxirannes de m&me type (les isomeres cis et trans du mCthoxy-3 cyclopentene et du methoxy-3 cyclohextne, aussi bien que les oxirannes provenant des olefines non-substitukes) sont traitks individuellement dans les mCmes conditions par une solution acide contenant des nucltophiles charges et non-charges (ion chlorure, eau et methanol). On rkalise aussi les scissions correspondantes catalysees par I'acide perchlorique. On met au point des mtthodes d'analyse prkcises et reproductibles des produits provenant du mklange rtactionnel. De cette f a~o n , les attaques nuclkophiles sur les differents oxirannes sont comparees directement. Les attaques de differents nuclkophiles sur le m&me oxiranne, ou par un seul nuclkophile ti diffkrentes positions du mdme oxiranne, sont comparees dans la m&me solution. Les resultats semblent apporter la demonstration la plus marquee connue jusqu'ti maintenant sur les effets d'orientation de charge. On rapporte la synthtse de quelques nouveaux diols trisubstituks-1,2,3 isomtres et de dimethoxyalcools.[Traduit par le journal]The mechanism of oxirane2 opening and the stereo-and regioselectivity of the nucleophilic addition have been topics of great interest (1-8).In these laboratories, we have expended a good deal of effort in this area due to our interest in conformational factors and the interaction of substituents in the cyclopentane and cyclohexane ring systems (see refs. 7-10 and references cited therein). In fact, it was the availability of compounds synthesized during these studies (for 'Present address: Defence Research Establishment Ottawa, Ottawa, Ont., Canada KIA 024.'For the remainder of this paper oxiranes will be designated as epoxides or cycloalkene oxides. These designations have been in use for many decades.example most of 1-19) (see Figs. la and 1b)which allowed us to proceed with the experiments described in this paper.Although several papers deal with the scission of 3-substituted cyclohexene or cyclopentene oxides (see, for example, refs. 7, 8, and 1...

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Konformationsanalyse, XII¹⁾Untersuchung der Konformerengleichgewichte von 2,4‐Diamino‐und 2,4‐Diazido‐2,4,6‐tridesoxy‐α‐D‐idopyransiden und 2,4‐Diazido‐2,4‐didesoxy‐β‐L‐xylopyransiden

Paulsen

Koebernick

1976

Chem. Ber.

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~ ~~Methyl-2,3-anhydro-6esoxy4O-ptolylsulfonyl-a-~allopyranosid (8) ergibt mit Hydrazin nach anschliehnder Hydrierung und Acetylierung direkt Methyl-2,4-diacetamido-3-0-acttyl-2,4,6 tridesoxy-a-D-idopyranosid (10). Mit Natriumazid ist aus 8 Methyl-2,4-diazido-2,4,6-tridesoxya-midopyranosid (12) (12). The influenct of 1,Zdiaxial interaction of dfierent substituents on conformational equilibria of idopyranow derivatives is studied. High proportions of 'C4 form and thus 1,3-diaxial interactions of great magnitude are observed in the case of diazido and diammonium idopyranoses 12 and 18, respectively. The origin of these effects is discussed.Methyl 2,4-diazido-and -3-0-acetyl-2,4diacttamido-2,Cdideoxy-~-~-xylop~anmide 23

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Konformationsanalyse, XIV ¹⁾ Bootkonformationen bei tert ‐Butylcyclohexan‐Derivaten durch polare 1,3‐diaxiale Wechselwirkungen

Cited by 7 publications

References 2 publications

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol

Konformationsanalyse, XII¹⁾Untersuchung der Konformerengleichgewichte von 2,4‐Diamino‐und 2,4‐Diazido‐2,4,6‐tridesoxy‐α‐D‐idopyransiden und 2,4‐Diazido‐2,4‐didesoxy‐β‐L‐xylopyransiden

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Konformationsanalyse, XIV 1) Bootkonformationen bei tert ‐Butylcyclohexan‐Derivaten durch polare 1,3‐diaxiale Wechselwirkungen

Cited by 7 publications

References 2 publications

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

Kristall- und Molekülstruktur der 1,4:3,6-Dianhydro-α-D-glucopyranose (1,5:3,6-Dianhydro-β-D-glucofuranose)

The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol

Konformationsanalyse, XII1)Untersuchung der Konformerengleichgewichte von 2,4‐Diamino‐und 2,4‐Diazido‐2,4,6‐tridesoxy‐α‐D‐idopyransiden und 2,4‐Diazido‐2,4‐didesoxy‐β‐L‐xylopyransiden

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Konformationsanalyse, XIV ¹⁾ Bootkonformationen bei tert ‐Butylcyclohexan‐Derivaten durch polare 1,3‐diaxiale Wechselwirkungen

Konformationsanalyse, XII¹⁾Untersuchung der Konformerengleichgewichte von 2,4‐Diamino‐und 2,4‐Diazido‐2,4,6‐tridesoxy‐α‐D‐idopyransiden und 2,4‐Diazido‐2,4‐didesoxy‐β‐L‐xylopyransiden