Verification of Biaryl-Structure Axial Chirality Produced in Ellagitannins by Chemical Oxidation.

The axial chirality of hexahydroxydiphenoyl (HHDP) groups contained in ellagitannins depends on the bridging position of d-glucose. The 4,6--HHDP group predominantly exhibits type chirality. This study elucidated the formation of the 4,6--()-HHDP group and subsequent axial isomerization by means of oxidative coupling of galloyl groups, which resulted in chirality.

Total Synthesis of Macaranin B.

This study describes the total synthesis of macaranin B, a naturally occurring ellagitannin containing 1-O-galloyl and 3,6-O-macaranoyl groups in an axial-rich d-glucose. The key steps of the synthesis include an oxidative coupling reaction of galloyl groups with 1,2,4-orthoacetylglucose moiety and oxa-Michael addition/elimination using an orthoquinone monoketal. This facilitates the construction of the macaranoyl group and the first total synthesis of macaranin B.

Total Synthesis of Casuarinin.

This study involves the total synthesis of casuarinin, a naturally occurring ellagitannin, in which an open-chain glucose is esterified with two ()-hexahydroxydiphenoyl (HHDP) groups. One HHDP group incorporates a C-glycosidic bond between its benzene ring and the glucose moiety, which was constructed with complete stereoselectivity using a benzyl oxime group that opened the glucopyranose ring and acted as a scaffold for C-glycoside production. This total synthesis enables future structure-activity relationship studies of this compound.

Synthesis of diaryl ether components of ellagitannins using ortho-quinone with consonant mesomeric effects.

Methods for synthesizing C-O digallate structures, the basic unit of diaryl ether components of natural ellagitannins, are described. In the designed building block derived from gallic acid, consonantly overlapped mesomeric effects enhanced its electrophilicity. This building block demonstrated substantial reactivity to improve the synthesis of dehydrodigalloyl, tergalloyl, and valoneoyl groups.

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins.

Cyclodextrins (CDs) are cyclic oligomers of α-1,4-d-glucopyranoside and are known mainly as hexamers to octamers. The central cavities of CDs can retain small molecules, enabling diverse applications. The smallest members, CD3 and CD4, have ring sizes too small to permit the most stable conformations of glucopyranose and have not been accessible synthetically.

Structural Revisions in Natural Ellagitannins.

Ellagitannins are literally a class of tannins. Triggered by the oxidation of the phenolic parts on β-pentagalloyl-d-glucose, ellagitannins are generated through various structural conversions, such as the coupling of the phenolic parts, oxidation to highly complex structures, and the formation of dimer and lager analogs, which expand the structural diversity. To date, more than 1000 natural ellagitannins have been identified.

Synthesis and Electron Paramagnetic Resonance Studies of Oligodeoxynucleotides Containing 2-N-tert-Butylaminoxyl-2'-deoxyadenosines.

Oligodeoxynucleotides (ODNs) containing 2-N-tert-butylaminoxyl-2'-deoxyadenosine (A*) residues were synthesized to allow accurate monitoring of adenine motion by EPR spectroscopy through the agency of direct linkage of the acyclic aminoxyl group to the nucleobase, and EPR studies of the ODNs in single- and double-stranded forms were performed. Upon duplex formation, peak broadening and decreases in peak height were observed in EPR spectra, and the synthesized ODNs were shown to be excellent monitors of hybridization. Comparison of peak height and the h /h signal ratio provided information on the relative mobility of A* in duplexes with different stability.