ABSTRACT
Application of intramolecular 1,3-dipolar nitrone cycloaddition reaction on carbohydrate-derived precursors containing an olefin functionality at C-1 or C-3 or C-5 and a nitrone moiety at C-2 or C-3 as appropriate has resulted in the formation of structurally new cycloaddition products containing furanose-fused oxepane, thiepane, azepane, cyclopentane, cycloheptane, tetrahydrofuran, and pyranose-fused tetrahydrofuran rings. The structure and stereochemistry of these products have been characterized by spectral as well as single-crystal X-ray analyses. Two of the compounds have been transformed to the bicyclic nucleoside derivatives applying Vorbrüggen reaction conditions.
Subject(s)
Alkenes/chemistry , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Carbohydrates/chemical synthesis , Nitrogen Oxides/chemistry , Nucleosides/chemical synthesis , Carbohydrates/chemistry , Crystallography, X-Ray , Cycloaddition Reaction , Furans/chemistry , Nucleosides/chemistry , StereoisomerismABSTRACT
Bis-, tris-, and tetrakisuracil-substituted 12-, 13-, 17-, and 21-membered macrocyclic nucleoside analogues with polyether linkages, including C2-symmetric molecules, have been synthesized through coupling of two appropriately allylated sugar derivatives, derived from D-glucose, followed by a sequential ring-closing metathesis reaction using Grubbs catalysts, double-bond reduction, and nucleoside base insertion under Vorbrüggen reaction conditions. Spectroscopic studies on the interaction of these nucleoside analogues with small molecules, such as the alkaloids berberine and palmatine and the DNA intercalator ethidium bromide, revealed a change in the absorbance and fluorescence of the small molecules suggesting the potential use of these nucleoside molecules as a carrier of small molecules in biological systems. Circular dichroism studies indicated that the complexes of the nucleosides with small molecules undergo aggregation/self-organization. This has been further evidenced by a SEM experiment showing the binding of berberine with one of the nucleoside derivatives, which confirms the occurrence of secondary structure reorganization.
Subject(s)
Carbohydrates/chemistry , Ethers/chemistry , Macrocyclic Compounds/chemistry , Nucleosides/chemistry , Circular Dichroism , GlycosylationABSTRACT
In 1-deoxy-xylofuranose derivatives possessing a good leaving group at 2-C, participation of allyloxy and propargyloxy substituents at 5-C results in loss of the 2-C substituent and attack of various nucleophiles at 5-C of the oxonium intermediate. Such participation of a benzyloxy or crotyloxy group leads to dioxabicyclo[2.2.1]heptane rings.
Subject(s)
Nucleosides/chemical synthesis , Xylose/analogs & derivatives , Xylose/chemical synthesis , Molecular Structure , Nucleosides/chemistry , Xylose/chemistryABSTRACT
Intramolecular nitrone cycloaddition (INC) reaction on a d-glucose derived substrate carrying an allyl group at C-1 and an enose-nitrone at C-5 or an aldehyde-nitrone at C-1 and vinyl group at C-4 furnished a tricyclo[6.2.1.0(2,6)]undecane or a tricyclo[5.2.1.0(2,6)]decane ring structure. These tricycles were converted to bicylic nucleosides with oxabicyclo[3.2.1]octane and oxabicyclo[2.2.1]heptane rings in three steps. An oxabicyclo[3.2.1]octane ring compound could alternatively be formed by RCM reaction between C-1-allyl and C-4-vinyl moieties and transformed to nucleoside analogues through a nucleophilic substitution reaction. Participation of a neighboring benzyl ether substituent in one case paved the way for an enantiodivergent synthesis.
Subject(s)
Bridged Bicyclo Compounds/chemical synthesis , Heptanes/chemistry , Nucleosides/chemistry , Octanes/chemistry , Cyclization , Glucose/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Nucleic Acid Conformation , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Installing hydroxymethyl and hydroxyethyl substitutions at C-4 through vinylation and hydroboration-oxidation reactions of the C-4 bis-hydroxymethyl derivative of d-glucose based substrate, and inserting heteroatoms thereafter permitted formation of N-, O-, or S-heterocycles leading to [4,5]- or [5,5]-spirocycles and a bicyclo[3.3.0]octane product. Some of the spirocycles were converted to spironucleosides under Vorbruggen glycosidation reaction conditions. Similarly, the bicyclic product was elaborated to the corresponding bicyclic nucleoside as well as an unexpected tricyclic nucleoside.
Subject(s)
Glucose/chemistry , Nucleosides/chemical synthesis , Cyclization , Magnetic Resonance Spectroscopy , Nucleosides/chemistry , Spectrometry, Mass, Electrospray IonizationABSTRACT
Treatment of the d-glucose-derived substrate 1 with sodium hydride in tetrahydrofuran provided 3,6-anhydro monosaccharide 2, along with the 5,6-ether linked pseudodisaccharide 3, and pseudotrisaccharide 4. However, reaction of 1 with sodium ethoxide in ethanol afforded 2 as the sole product, elaborated to the bicyclic azidonucleosides 9 and 16. Acetylated bicyclic nucleosides 17-19 with extended carbohydrate residues have been synthesized from 3.
Subject(s)
Carbohydrates/chemistry , Nucleosides/chemistry , Polysaccharides/chemistry , Bacillus thuringiensis/metabolism , Carbohydrate Conformation , Carbohydrate Sequence , Crystallography, X-Ray/methods , Dose-Response Relationship, Drug , Glucose/chemistry , Magnetic Resonance Spectroscopy/methods , Models, Chemical , Molecular Conformation , Molecular Structure , Spectrometry, Mass, Electrospray Ionization , TemperatureABSTRACT
Carbohydrate-derived substrates having (i) C-5 nitrone and C-3-O-allyl, (ii) C-4 vinyl and a C-3-O-tethered nitrone, and (iii) C-5 nitrone and C-4-allyloxymethyl generated tetracyclic isoxazolidinooxepane/-pyran ring systems upon intramolecular nitrone cycloaddition reactions. Deprotection of the 1,2-acetonides of these derivatives followed by introduction of uracil base via Vorbrüggen reaction condition and cleavage of the isooxazolidine rings as well as of benzyl groups by transfer hydrogenolysis yielded an oxepane ring containing bicyclic and spirocyclic nucleosides. The corresponding oxepane based nucleoside analogues were prepared by cleavage of isoxazolidine and furanose rings, coupling of the generated amino functionalities with 5-amino-4,6-dichloropyrimidine, cyclization to purine rings, and finally aminolysis.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/chemical synthesis , Glucose/chemistry , Nucleosides/chemical synthesis , Spiro Compounds/chemical synthesis , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Molecular Conformation , Nucleosides/chemistry , Spiro Compounds/chemistry , StereoisomerismABSTRACT
The carbohydrate-derived substrate 3-C-allyl-1,2:5,6-di-O-isopropylidene-alpha-D-allofuranose was judiciously manipulated for preparing suitable synthons, which could be converted to a variety of isoxazolidino-spirocycles and -tricycles through the application of ring-closing metathesis (RCM) and intramolecular nitrone cycloaddition (INC) reactions. Cleavage of the isoxazolidine rings of some of these derivatives by transfer hydrogenolysis followed by coupling of the generated amino functionalities with 5-amino-4,6-dichloropyrimidine furnished the corresponding chloropyrimidine nucleosides, which were elaborated to spiroannulated carbanucleosides and conformationally locked bicyclo[2.2.1]heptane/oxa-bicyclo[3.2.1]octane nucleosides. However, use of higher temperature for the cyclization of one of the chloropyrimidines led to the dimethylaminopurine analogue as a sole product, formed via nucleophilic displacement of the chloro group by dimethylamine generated from DMF.
Subject(s)
Glucose/analogs & derivatives , Nitrogen Oxides/chemistry , Nucleosides/chemistry , Cyclization , Glucose/chemistry , Molecular ConformationABSTRACT
Using Vorbrüggen's protocol, reaction of persilylated uracil with xylofuranose derivatives having 3beta-oxy-3alpha-alkyl substitution produced both alpha- and beta-nucleosides. Only the beta-nucleosides were formed from substrates having the reverse stereochemistry at C-3 or lacking the 3-alkyl substituent. Participation of the 3beta-oxy substituent in stabilizing the incipient C-1 carbonium ion (or oxonium ion) intermediate has been suggested from analysis of energy-minimized conformations.
Subject(s)
Carbohydrates/chemistry , Nucleosides/chemistry , Nucleosides/chemical synthesis , Alkylation , Molecular Structure , Oxidation-ReductionABSTRACT
The dioxepanofuranose derivatives 4 and 12, obtained through the cyclization of the 3-(2-hydroxyethyl) ether of a D-xylo-pentodialdose derivative, were appropriately functionalized and elaborated to the first examples of the new class of 3'-O and 5'-O-bicyclic nucleoside analogues 9, 10, and 14 with a fused seven-membered ring. Reactions carried out through the intermediacy of the D-xylo-pentodialdose derivative 5 yielded racemic products, while prior protection of the 4-formyl group (as in 7) before deprotection of the 1,2-hydroxyl groups led to optically active analogues.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/chemistry , Glucose/chemistry , Nucleosides/chemistry , Cyclization , Molecular Structure , Nucleosides/chemical synthesis , StereoisomerismABSTRACT
A simple synthesis of chiral spironucleosides and spirobisnucleosides is described. Intramolecular 1,3-dipolar nitrone cycloaddition reaction of d-glucose-derived precursors having olefin at C-3 and nitrone at C-5, C-1, or C-2 (in nor-series) furnished bisisoxazolidinospirocycles 4-7, 11, and 12 in good yields. Reductive ring opening of the isoxazolidine moieties in 4-6 followed by construction of a nucleoside base upon the generated amino groups smoothly yielded spirobisnucleosides 17 and 18 and spironucleosides 20 and 21.