The gauche effect

Зефиров, Н. С.; Samoshin, Vyacheslav V.; Subbotin, O. A.; Baranenkov, V.I.; Wolfe, Saul

doi:10.1016/0040-4020(78)88017-x

Cited by 90 publications

(29 citation statements)

References 48 publications

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“…For instance, when passing from a nonpolar solvent (C 6 D 6 ) to a more polar solvent (CDCl 3 ), the signals for the protons at the substituents in the spectra of compounds 2a,b become broadened, thus confirming the trans arrangement of the halogen atom and the phenylthio group. 15 The coupling constant in the 1 H NMR spectra of compounds 4a,b (J 2,3 ≈ 3 Hz) is also consistent with the trans arrangement of the substituents. 16 The absence of the products of the Wagner-Meerwein rearrangement in the case of norbornene is indicative of the low effective electrophilicity of the sulfenylating sys tems.…”

Section: Methodssupporting

confidence: 58%

A new method for the activation of ethyl benzenesulfenate in electrophilic addition reactions

et al. 2008

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Reactions of unsaturated compounds with the PhSOEt-SOHal 2 and PhSOEt-Me 3 SiHal systems (Hal = Cl or Br) were proposed as a new route to haloalkyl phenyl sulfides. With acyclic and mono and bicyclic alkenes and dienes as examples, the regio and stereoselectivity of the reactions were studied.Electrophilic addition of such sulfenic acid derivatives as sulfenyl chlorides is a well studied and convenient route to sulfur containing compounds. 1 Sulfenylbromination, 2,3 iodination, 4 and fluorination 5 have been studied less thoroughly because of the low stability of the starting sulfe nyl halides. Addition of stable sulfenic acid derivatives (sulfenamides) to multiple bonds occurs only in the pre sence of strong protic 3 or Lewis acids. 2,4-8 It should be noted that halosulfenylation, 2-6 aminosulfenylation, 7 or sulfamatosulfenylation 8 are possible when an appropriate activator is employed. Only a few studies have been devot ed to the sulfenylation of unsaturated compounds with sulfenic acid esters (sulfenates). 9-12 Earlier, we have reported on new methods for halo sulfenylation of olefins through their reactions with ethyl benzenesulfenate in the presence of phosphorus oxoha lides 13 and trimethylsilyl halides. 14 In the present work, we studied the possibility of sulfenylating alkenes and dienes with ethyl benzenesulfenate in the presence of trimethylsi lyl halides and thionyl halides.These reactions are very easy to implement: a solution of a coreagent (SOHal 2 or Me 3 SiHal; Hal = Cl or Br) is slowly added to a solution of an alkene and a sulfenate in chloroform (or dichloromethane) and the mixture is stirred at room temperature until the reaction is completed (15-20 min). Then the mixture is passed through a col umn with silica gel and the eluate is concentrated. In most cases, the resulting product requires no additional purifi cation. The structures of the products were determined by 1 H and 13 C NMR spectroscopy. The compositions of the novel compounds were confirmed by GC MS or elemen tal analysis data.The reactions of ethyl benzenesulfenate with cyclohex ene and norbornene (Scheme 1) in the presence of SOHal 2 (Hal = Cl or Br), as in the case of Me 3 SiHal, proceed stereospecifically to give trans β haloalkyl phenyl sulfides in nearly quantitative yields (Table 1). Scheme 1Hal = Cl (2a, 4a), Br (2b, 4b)

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Section: Methodssupporting

confidence: 58%

A new method for the activation of ethyl benzenesulfenate in electrophilic addition reactions

et al. 2008

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“…The trans orientation of the C(4')-0(11) and C(5')-O(5') bonds, corresponding to the gauche-rotamer in nucleosides, is energetically the least stable one (14). In the other two molecules, these two bonds are in the preferred gauche conformation, but the increased stability is estimated to be only 0.65 kcal/mol (15). If the 2: 1 equilibrium found in the crystal structure existed in solution as well, the energy difference between the two conformers would amount to about 0.4 kcal/mol.…”

Section: Solid State Conformationmentioning

confidence: 99%

Conformational features of acyclonucleosides: structure of acyclovir, an antiherpes agent

Birnbaum¹,

Cygler²,

Shugar³

1984

Can. J. Chem.

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GEORGE 1. BIRNBAUM, MIROSLAW CYCLER, and DAVID SHUGAR. Can. J . Chem. 62, 2646Chem. 62, (1984. Crystals of acyclovir belong to the space group P2,/n, and the cell dimensions are a = 25.459(1), b = 11.282 (I), c = 10.768(1) A, P = 95.16(1)". Intensity data were measured on a diffractometer and the structure was determined by direct methods. The asymmetric unit was found to contain three independent molecules of acyclovir and two molecules of water. Least-squares refinement, which included all hydrogen atoms, converged at R = 0.053 for 3970 observed reflections. In two of the molecules the side chain is partially folded, while in the third one it is fully extended. The glycosidic torsion angles are in the range 91.4-104.3". The conformational features are compared with those in other known acyclonucleosides. They are also examined in relation to the behavior of acyclonucleosides and acyclonucleotides in various enzymatic systems, including those related to antiviral activities. (1) that replacement of the ribose moiety of guanosine by an acyclic chain corresponding to the "upper" portion of the ribose ring led to an analogue, 9-[(2-hydroxyethoxy)methyl]guanine (acycloG, acyclovir, ACV), with potent antiherpes activity. Interest in this compound, now licensed for clinical use, was further enhanced by the finding that, in HSV-infected cells, its mechanism of action was due to its specific phosphorylation by the viral-encoded (but not cellular) thymidine kinase to acyclo-GMP (l), followed by further phosphorylation by cellular GMP and GDP kinases to the triphosphate, acycloGTP, which is a selective and potent inhibitor of the HSV DNA polymerase (2).

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“…trans-1,2-Cyclohexanediols and trans-2-aminocyclohexanols are well known to strongly prefer the diequatorial conformation, in part due to an intramolecular hydrogen bonding between vicinal substituents. 20,23,[39][40][41][42] Therefore, these structural moieties can be used as conformational counterbalances or locks.…”

Section: Methodsmentioning

confidence: 99%

Trans-2-aminocyclohexanols as pH-triggered molecular switches

Brazdova¹,

Koo²,

Wong³

et al. 2005

Arkivoc

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Cyclohexane-based conformationally controlled ionophores, the emerging new class of molecular switches, provide a new and promising approach to allosteric systems with negative cooperativity. Protonation of trans-2-aminocyclohexanols leads to dramatic conformational changes: due to an intramolecular hydrogen bond, a conformer with equatorial position of ammonio-and hydroxy-groups becomes predominant. Thus, these structures can serve as powerful conformational pH-triggers. The trans-2-aminocyclohexanol moiety has been used for pH-triggered conformational switching of a crown ether and a podand, and their complexes with potassium ion.

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The gauche effect

Cited by 90 publications

References 48 publications

A new method for the activation of ethyl benzenesulfenate in electrophilic addition reactions

A new method for the activation of ethyl benzenesulfenate in electrophilic addition reactions

Conformational features of acyclonucleosides: structure of acyclovir, an antiherpes agent

Trans-2-aminocyclohexanols as pH-triggered molecular switches

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