Intramolecular Participation Research Articles

Characterization of Acyl Adenyl Anhydrides: Differences in the Hydrolytic Rates of Fatty Acyl-AMP and Aminoacyl-AMP Derivatives

An improved procedure has been developed to prepare RCOOPO2-Ado (R = C6H13 and C15H31), the intermediate in the enzymatic synthesis of acyl-CoA's. The product has been characterized by spectral methods which, in turn, were used to define the hydrolysis rates of RCO-AMP. When R is a fatty acyl group, the hydrolysis rate is 10-fold slower than when R is aminoacyl. In both cases, the hydrolysis rate is enhanced by Mg2+. We speculate that the rate acceleration is due to intramolecular participation of the second carbonyl group in the aminoacyl residue.

Acceleration of the Zn2+-promoted phosphodiester hydrolysis of oligonucleotides by the 3′-terminal monophosphate group: intrastrand participation over several nucleoside units

The Zn2+-promoted hydrolysis of the 5′-terminal ribonucleoside phosphodiester bond in chimeric ribo/deoxyribo oligonucleotide 3′-monophosphates, Up(Tp)4 and Up(Tp)9, and their dephosphorylated analogue, Up(Tp)3T, has been studied at various metal ion and substrate concentrations, and in the presence and absence of deoxyribooligonucleotide 3′-monophosphates, (Tp)n, containing no cleavable ribonucleoside phosphodiester bond. The results strongly suggest that the rate-accelerating effect of the 3′-terminal monophosphate group on the phosphodiester hydrolysis is of intramolecular origin: the Zn2+ ion bridges the favoured site of coordination, i.e. the terminal monophosphate group, and the cleaving phosphodiester bond. The 3′-monophosphate group also causes the reaction order in [Zn2 +] to deviate from unity, the values obtained with Up(Tp)3T, Up(Tp)4 and Up(Tp)9 being 1.1, 1.4 and 1.7, respectively. Possibly, the intramolecular participation of the 3′-monophosphate bound Zn2+ ion is facilitated by another Zn2+ ion that stabilizes the folded conformation of the oligonucleotide chain in the reactive Zn2 +/substrate macrochelate.

ChemInform Abstract: Catalytic Intramolecular Participation of Amide Group in the Acid Hydrolysis of Methyl Ether Linkage.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Selective 5′-desilylation of 3′,5′-disilyi AraU derivatives under basic conditions

3′,5′-di- tert-butyldimethylsilyl-2,2′-anhydrouridine 3 was hydrolyzed under basic conditions to yield selectively 3′- tert-butyldimethylsilylarabinouridine 5 in 85 % yield. 3′,5′-disilyl-arabinouridine derivatives 4 and 6 also led selectively to 5 under the same conditions. These reactions suggest an intramolecular participation of the 2′-hydroxyl group in the desilylation and can be used to prepare rapidly and in high yield 3′-silylaraU derivatives.

Catalytic intramolecular participation of amide group in the acid hydrolysis of methyl ether linkage

Evidence for the acid catalysed hydrolysis of methyl ether linkage assisted by the neighboring amide function was obtained The hydrolysis rate of 1 to 3 was measured at least 1.7×10 3 fold higher than that of the reference compound 5 The values of thermodynamic parameters suggest that the participation of neighboring amide group in 1 is accompanied by a lower activation enthalpy with respect to the unassisted reaction in 5. Experimental evidence, such as the kinetic isotope ratio, the positive σ value of Bunnett-Olsen equation and ΔS ++ value suggests an A2 mechanism

ChemInform Abstract: Application of the Mitsunobu Reaction to Ephedrines and Some Related Amino Alcohols. Aspects of Intramolecular Participation of the Amino Group.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Preparation of (4‐t‐Butyl‐2,6‐bis(N,N‐dimethylaminomethyl)phenyl) thioxophosphine Sulfide with Intramolecular Participation of Nitrogen Lone Pair in Stabilization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of [4-t-Butyl-2,6-bis(N,N-dimethylaminomethyl)phenyl]thioxophosphine Sulfide with Intramolecular Participation of Nitrogen Lone Pair in Stabilization

Abstract The 4-t-butyl-2,6-bis(N,N-dimethylaminomethyl)phenyl group was utilized to prepare [4-t-butyl-2,6-bis(N,N-dimethylaminomethyl)phenyl]thioxophosphine sulfide. A 31P NMR chemical shift of the thioxophosphine sulfide shows a high field shift by 153 ppm compared with that of (2,4,6-tri-t-butylphenyl)thioxophosphine sulfide, suggesting a strong intramolecular participation with the lone-pair electrons of the nitrogen atom in stabilization of the –P(=S)2 group.

Application of the Mitsunobu reaction to ephedrines and some related amino alcohols. Aspects of intramolecular participation of the amino group

AbstractInversion of configuration at the benzylic hydroxyl group of (1S,2S)‐pseudoephedrine (2) to afford (1R,2S)‐ephedrine is known to be a difficult process. The Mitsunobu reactions of 1 and 2 might offer a route to achieve such inversions. In fact Mitsunobu reactions on 1 and 2 are known to proceed via aziridines formed on intramolecular SN2 substitution by the amine functionality. The Mitsunobu reactions of N‐methylated and N‐benzylated ephedrines have been found to proceed via the corresponding aziridinium ions. These aziridinium ions can be opened (SN2 substitution) by nucleophiles like phthalimide and thiols. Intramolecular participation in 2 can be avoided by use of the tert‐butyloxycarbonyl‐ (BOC) or benzyloxycarbonyl‐ (CBZ) protected derivatives. Mitsunobu reactions on these derivatives lead to inversion of configuration at the benzylic hydroxyl center. In contrast the BOC and CBZ derivatives of 1 are deprotected under Mitsunobu conditions. The Mitsunobu reactions of threo (1S,2,S)‐2‐amino‐1,3‐propanediol have also been examined. An attempt to achieve protection by reaction with dimethylformamide dimethyl acetal led to the more substituted 2‐oxazoline as established by X‐ray crystallography. The desired inversion of configuration of the benzylic hydroxylic group was eventually achieved by protection of the amino substituent as the phthalimide and protection of the primary hydroxyl group as the tosylate.

Nucleophilic substitutions using O‐alkyl‐N,N′‐dialkylisoureas. Applications to ephedrines

AbstractDialkylcarbodiimides in the presence of a Cu1 catalyst react cleanly with the hydroxyl group of N‐methylated (1R,2S)‐ephedrine and (1S,2S)‐pseudoephedrine. These adducts react with nucleophiles like alkyl and aryl thiols as well as thioic acids and phthalimide to form the substitution products with overall retention of configuration. It is postulated that intramolecular participation of the amino group via an SN2 reaction leads to aziridium salts, which are subsequently opened by the nucleophiles via a second SN2 reaction. This synthetic approach is also useful for the inversion of simple secondary alcohols; on treatment with dicyclohexylcarbodiimide followed by benzothioic acid and treatment with LiAlH4, menthol was converted in good yield to neomenthane thiol.

Ozonolysis of Amino Alkenes Derived From Labda-8(17),14-dien-13-ol

A series of amino alkenes was synthesized from manool [labda-8(17),14-dien-13-ol] as substrates for an investigation of the ability of an amino group to act as an internal nucleophile during ozonolysis. A 10-membered ring keto lactam (20) was produced from amino. alkene (4) but the C8-C9 bond remained intact during the ozonolysis of amino alkene (18). Substrates with an unfavourable relationship of the amino group to the olefin, (7), (10) and (16), gave no products resulting from intramolecular participation.

Spongian pentacyclic diterpenes. Stereoselective synthesis of aplyroseol-1, aplyroseol-2 and deacetylaplyroseol-2

Natural spongian pentacyclic diterpenes aplyroseol-1 19, aplyroseol-2 18 and deacetylaplyroseol-2 17 have been synthesized in enantiomerically pure form from (+)-podacarp-8(14)-en-13-one 3. Key intermediate in these syntheses is a suitably substituted acid-dialdehyde 2, which is prepared from enone 3 by a sequence of transformations involving stereoselective introduction of a C-7 oxygen functionality, photoaddition of acetylene to the C(8)–C(14) double bond to form a cyclobutene ring system, reductive cyanation of the C-13 carbonyl group, hydrolysis of the resulting nitrile group, and ozonolysis of the cyclobutene moiety. An intramolecular participation of the 7α-hydroxy group in the hydrolysis of the 13α-nitrile 8 is set in focus.

Siloxane equilibration during the condensation reactions of organosilicon functional amines and anhydrides

The condensation reaction between amines and anhydrides in which one or both of the reactants contain siloxane functionality usually affords imide products in which siloxane redistribution has occurred. The reaction is catalyzed by the amic acid intermediate and prevails when geometry is favorable for intramolecular participation. Poly(imide siloxanes) prepared via this type of condensation process will contain scrambled repeat units in the backbone and will produce cyclic siloxanes as coproducts as a result of the redistribution process

Intramolecular thioamide participation reactions

The intramolecular participation of the thioamide group during the attempted formation of 10 and 13 from 8 , led to the stereospecific formation of the versatile bicyclic intermediates 9 and 14 respectively. Their use as valuable precursors to tetrahydroisoindazoles of type 3 (X √; N) is demonstrated.

Chemoselective reactioms of 14,17α-bis(hydroxymethyl)-3-methoxyestra-1,3,5(10)-trien-17β-ol. Synthesis of novel 14,17-hetero-bridged 19-norsteroids

Chemoselective differentiation of the primary hydroxy groups in 14,17α-bis(hydroxymethyl)-3-methoxyestra-1,3,5(10)-trien-17β-ol ( 2) has been investigated in a series of reactions which lead inter alia to novel 14,17-hetero-bridged steroid hormone analogues. Thus routes are described to 3-methoxy-14,17α-(2-oxapropano)estra-1,3,5(10)-trien-17β-ol ( 4) and 17α 14-epoxymethano-17β-hydroxymethyl-3-methoxyestra-1,3,5(10)-triene ( 8). Related experiments show that the 17 1-hydroxy group in ( 2) is preferentially functionalised and that 17 1-tosyloxy 14 1-ethers undergo facile intramolecular participation reactions. The utility of certain intermediates in the synthesis of hormone analogues is exemplified by conversion of ( 8) into 17α,14-epoxymethano-19-norpregn-4-ene-3,20-dione ( 36).

Intramolecular participation of the amide group in acid- and base-catalysed phosphonate monoester hydrolysis

Rates of hydrolysis of monoaryl α-amidophosphonates in both acid and alkaline solutions are much greater than those of comparable compounds lacking the amido substituent; intramolecular nucleophilic catalysis seems likely. This phenomenon may be important in the employment of α-amidophosphonate derivatives as enzyme inhibitors.

Antigenic determinants and functional domains in core antigen and e antigen from hepatitis B virus

The precore/core gene of hepatitis B virus directs the synthesis of two polypeptides, the 21-kilodalton subunit (p21c) forming the viral nucleocapsid (serologically defined as core antigen [HBcAg]) and a secreted processed protein (p17e, serologically defined as HBe antigen [HBeAg]). Although most of their primary amino acid sequences are identical, HBcAg and HBeAg display different antigenic properties that are widely used in hepatitis B virus diagnosis. To locate and to characterize the corresponding determinants, segments of the core gene were expressed in Escherichia coli and probed with a panel of polyclonal or monoclonal antibodies in radioimmunoassays or enzyme-linked immunosorbent assays, Western blots, and competition assays. Three distinct major determinants were characterized. The single conformational determinant responsible for HBc antigenicity in the assembled core (HBc) and a linear HBe-related determinant (HBe1) were both mapped to an overlapping hydrophilic sequence around amino acid 80; a second HBe determinant (HBe2) was assigned to a location in the vicinity of amino acid 138 but found to require for its antigenicity the intramolecular participation of the extended sequence between amino acids 10 and 140. It is postulated that HBcAg and HBeAg share common basic three-dimensional structure exposing the common linear determinant HBe1 but that they differ in the presentation of two conformational determinants that are either introduced (HBc) or masked (HBe2) in the assembled core. The simultaneous presentation of HBe1 and HBc, two distinctly different antigenic determinants with overlapping amino acid sequences, is interpreted to indicate the presence of slightly differently folded, stable conformational states of p21c in the hepatitis B virus nucleocapsid.

Anchimeric assistance with intermediary N-alkoxyaziridinium salts. Formation of vicinal aminoalcohols and derivatives

Intramolecular iodoaminations have afforded pyrrolidino iodides. Iodides are transformed to β-aminoalcohols with net retention of configuration. Intramolecular participation of proximate esters results in a double ring closure of cyclic amination and vicinal lactonization.

ChemInform Abstract: Stereo‐ and Regiocontrol of Electrophilic Additions to Cyclohexene Systems by Neighboring Groups: Participation of Allylic and Homoallylic Ester Groups in Hypobromous Acid Addition to Some 5‐Unsaturated Cholestane Derivatives.

AbstractHypobromous acid addition to some cholestenes such as (I) proceeds with intramolecular participation of the neighboring acetoxy groups.

ChemInform Abstract: Kinetics of Hydrolysis of 1‐Acetoxy‐, 1‐Acetoxy‐8‐hydroxy‐, and 1,8‐Diacetoxynaphthalenes: Intramolecular Participation by a Hydroxy Group.

ChemInformVolume 19, Issue 30 Preparative Organic Chemistry ChemInform Abstract: Kinetics of Hydrolysis of 1-Acetoxy-, 1-Acetoxy-8-hydroxy-, and 1,8-Diacetoxynaphthalenes: Intramolecular Participation by a Hydroxy Group. F. HIBBERT, F. HIBBERT Dep. Chem., King's Coll., London WC2R 2LS, UKSearch for more papers by this authorK. J. SPIERS, K. J. SPIERS Dep. Chem., King's Coll., London WC2R 2LS, UKSearch for more papers by this author F. HIBBERT, F. HIBBERT Dep. Chem., King's Coll., London WC2R 2LS, UKSearch for more papers by this authorK. J. SPIERS, K. J. SPIERS Dep. Chem., King's Coll., London WC2R 2LS, UKSearch for more papers by this author First published: July 26, 1988 https://doi.org/10.1002/chin.198830136AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue30July 26, 1988 RelatedInformation