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.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/jo070846m | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Stereoselective Entry into α,α'-C-Oxepane Scaffolds through a Chalcogen Bonding Catalyzed Strain-Release C-Septanosylation Strategy.
Angew Chem Int Ed Engl
July 2024
Abteilung Chemische Biologie, Max Planck Institut für Molekulare Physiologie, Otto-Hahn-Straße 11, 44227, Dortmund, Germany.
The utility of unconventional noncovalent interactions (NCIs) such as chalcogen bonding has lately emerged as a robust platform to access synthetically difficult glycosides stereoselectively. Herein, we disclose the versatility of a phosphonochalcogenide (PCH) catalyst to facilitate access into the challenging, but biologically interesting 7-membered ring α,α'-C-disubstituted oxepane core through an α-selective strain-release C-glycosylation. Methodically, this strategy represents a switch from more common but entropically less desired macrocyclizations to a thermodynamically favored ring-expansion approach.
View Article and Find Full Text PDFBlue- and Red-Shifting C-H⋯O Hydrogen Bonds of Cyclic Ethers with Haloforms: Effect of Ring-Size and Consistency with Bent's Rule.
Chemphyschem
July 2024
Department of Chemistry, Mahadevananda Mahavidyalaya, Kolkata, 700 120, India.
A DFT-based computational study is carried out to delve into the interplay between hyperconjugation and rehybridization effects underlying the formation of blue- or red-shifting H-bonds (HBs) in 1 : 1 complexes of cyclic ethers (HB acceptor) of varying ring-size with haloforms, CHF and CHCl (HB donor). The calculations reveal that with decreasing angular strain (increasing ring-size) of the cyclic ethers, the extent of blue-shift increases for 1 : 1 complexes with CHF, while a reverse sequence is observed with CHCl, eventually leading to a red-shifting HB in the oxepane : CHCl complex. It is noted that the trend in the shift of C-H stretching fundamental is not mirrored by the C-H bond length or interaction energies for both the systems studied, that is, the low sensitivity of the changes on the strain on the O-atom of HB acceptor (cyclic ethers) is to be emphasized.
View Article and Find Full Text PDFSynthesis of Cycloartan-16β-ol from 16β 24R-Epoxy-Cycloartane and Their Cytotoxicity Evaluation Against Human Cancer Cell Lines.
Chem Biodivers
May 2024
Departmento de Productos Naturales, Instituto de Química, Universidad Nacional Autónoma de México. C. Exterior, C. Universitaria, Ciudad de México, Coyoacán, 04510 DCMX, México.
It was found that Argentatins A and B triterpenoids make up approximately 20-30 % of the waste resin produced from the industrial processes to isolate rubber from P. argentatum. We have developed an efficient protocol for synthesizing cycloartane-16β-ol derivatives by opening the oxepane ring of argentatin B acetate (2) with BF-OEt.
View Article and Find Full Text PDFConstruction of Seven-Membered Oxacycles Using a Rh(I)-Catalyzed Cascade C-C Formation/Cleavage of Cyclobutenol Derivatives.
J Org Chem
April 2024
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Article Synopsis
- The study details the synthesis of substituted oxepane derivatives using a method that involves remodeling 4-hydroxy-2-cyclobutenones, which are made from dialkyl squarates reacting with acrylonitrile.
- A mechanism involving a Rh(I)-catalyzed process is proposed, where a fused [3.2.0] bicycle structure forms via a series of reactions, including an oxa-Michael addition and an intramolecular rearrangement, ultimately leading to the oxepane ring.
- Computational studies indicate that while a certain intermediate forms, there's an alternative pathway through a Rh(III) intermediate, and the process is noted to retain stereochemistry, allowing for further modifications of the resultant
Radical ring-opening polymerization (rROP) has received renewed attention to incorporate cleavable linkages into the backbones of vinyl polymers, especially from cyclic ketene acetals (CKAs). Among the monomers that hardly copolymerize with CKAs are (1,3)-dienes such as isoprene (I). This is unfortunate since synthetic polyisoprene (PI) and its derivatives are the materials of choice for many applications, in particular as elastomers in the automotive, sport, footwear, and medical industries, but also in nanomedicine.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!