title: Functionalization of cyclodextrins via reactions of 2,3-anhydrocyclodextrins.
abstract: Three types of reactions of 2,3-anhydro-beta-cyclodextrins, namely nucleophilic ring-opening, reduction to 2-enopyranose, and reduction to 3-deoxypyranose, have been investigated to regio- and stereoselectively functionalize the secondary face of beta-cyclodextrin. Upon treatment with various nucleophiles, both 2,3-mannoepoxy and 2,3-alloepoxy-beta-cyclodextrins are found to undergo nucleophilic ring-opening reaction generating 3- and 2-modified cyclodextrin derivatives. In each case, the 3-position is more easily accessible than the 2-position. By using these ring-opening reactions, imidazolyl, iodo, azido, and benzylmercapto groups are selectively introduced to the secondary face of beta-cyclodextrin in place of the 2- or 3-hydroxyl groups. The functionalized cyclodextrins have either modified glucosidic subunits or modified altrosidic subunits that make the hydrophobic cavity slightly distorted from that of native beta-cyclodextrin. Thiourea also reacts with the cyclodextrin epoxides. In this case, thiirane and olefin species are generated instead of any ring-opening products. By ameliorating the reaction condition, cyclodextrin olefin, diene, and triene derivatives are prepared in moderate to good yields. Reduction of per[6-(tert-butyldimethyl)silyl]-beta-cyclodextrin permannoepoxide with lithium aluminum hydride produces the per(3-deoxy)-beta-cyclomannin. All these chemically modified cyclodextrins are structurally well characterized and most of them are expected to serve as versatile scaffolds for diverse purposes such as the construction of catalysts and development of synthetic receptors and molecular containers.
authors: Department of Molecular Medicinal Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan. deqiyuan@net.nagasaki-u.ac.jp
authors: De-Qi
authors: DQ
authors: Yuan
authors: Tsutomu
authors: T
authors: Tahara
authors: Wen-Hua
authors: WH
authors: Chen
authors: Yuji
authors: Y
authors: Okabe
authors: Cheng
authors: C
authors: Yang
authors: Youichi
authors: Y
authors: Yagi
authors: Yasuyoshi
authors: Y
authors: Nogami
authors: Makoto
authors: M
authors: Fukudome
authors: Kahee
authors: K
authors: Fujita
mesh_terms: D001667:Binding, Competitive; D003505:Cyclodextrins / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013890:Thiourea / Q000737:chemistry
chemical_list: D003505:Cyclodextrins; D004852:Epoxy Compounds; D013890:Thiourea