Yasuyoshi Nogami

Guest-induced conformational change in a flexible host: mono-altro-β-cyclodextrin †

Mono-altro--cyclodextrin 1 ,a -cyclodextrin with one of the seven glucose units being configurationally changed to an altrose, is shown to be a flexible host undergoing a distinct conformational change within its altropyranose geometry upon intracavity inclusion of adamantanecarboxylate, thus representing an induced-fit model of binding rather than one following the rigid lock-and-key type pattern.

General method for preparing altrosides from 2,3-manno-epoxides and its application to synthesis of alternative β-cyclodextrin with an altroside as the constituent of macrocyclic structure

Abstract A general and convenient method for preparing altrosides from 2,3-manno-epoxides is described and as the application, 2A(S),3A(R)-β-Cyclodextrin which has an altroside as the constituent was prepared and assigned;the altroside part has 1C4 conformation predominantly.

DEPENDENCE OF GUEST-BINDING ABILITY ON CAVITY SHAPE OF DEFORMED CYCLODEXTRINS

Abstract Guest-binding ability of some β-cyclodextrin derivatives with deformed cavities were dependent on the cavity shapes, where 2,3′-anhydro-β-cyclodextrin 3 bound methyl orange about 2.8 times stronger than native β-cyclodextrin at 10°C.

Per(3-deoxy)-γ-cyclomannin: a non-glucose cyclooligosaccharide featuring inclusion properties

Abstract Per(3-deoxy)-γ-cyclomannin has been efficiently synthesized by a three-step procedure starting from natural γ-cyclodextrin, and proved to be capable of binding naphthalenesulfonate in aqueous solution and solubilizing C 60 in water. For the first time it was spectrally evidenced that a non-glucose cyclooligosaccharide did form inclusion complexes with conventional organic guest molecules.

The 2,3-anhydro-α-cyclomannin−1-propanol hexahydrate: topography, lipophilicity pattern and solid-state architecture

Abstract As evidenced by its X-ray structural analysis, 2,3-anhydro-α-cyclomannin 6 , a cyclooligosaccharide consisting of six α-(1→4)-linked 2,3-anhydro -d- mannopyranose units, readily incorporates 1-propanol into its cavity such that hydrophobic and hydrophilic surface regions of guest and host match at their interfaces. Together with water, the macrocycle and its guest assemble into a unique solid-state architecture, featuring layers of head-to-head dimers of the macrocycle with its guest, separated by equally distinct layers of water molecules, which are engaged in an intense hydrogen bonding network with the 6-CH 2 OH and the propanol-OH groups. The overall guest–host topography is thus reverse to that of the respective ethanol inclusion complex. 1

Structure and Lipophilicity Profile of 2, 3‐Anhydro‐α‐cyclomannin and Its Ethanol Inclusion Complex

Readily available from alpha-cyclodextrin in three steps, 2,3-anhydro-alpha-cyclomannin composed of six alpha-(1-->4)-linked 2,3-anhydro-D-mannopyranose residues, crystallizes well when precipitated from aqueous ethanol. An X-ray structure reveals the macrocycle to contain ethanol in its cavity, thus representing the first inclusion complex of a non-glucose cyclooligosaccharide. The wider rim of the torus-shaped macrocycle holds the six epoxide rings whose oxygens point away from the cavity, thereby sculpturing the unique over-all shape of a six-pointed star.

Silver(1) ion catalyzed substitution reactions: stereoelectronic control in an SN1 mechanism

Stereochemistry of the acetolysis of 4-, 6α- and 6β-bromocholest-4-en-3-ones using silver acetate was established, and the reactions were interpreted to proceed via a stereoelectronically controlled SN1 mechanism.

The isolation of a spiran in the rearrangement of an α-bromo-α,β-unsaturated steroidal ketone

Abstract A new acid-catalyzed aromatization of 3-bromocholest-2-en-4-one has been found and a spiranic product is really captured in this rearrangement.

A Mild And Efficient Synthesis of Diamino-Steroids

Abstract α γ-Dibromo-α β-enones readily react with various secondary cyclic amines at ambient temperature to afford the corresponding α γ-diamino-enones in high yields.

Reaction of α-Halo-Enones with Heterocyclic Bases. A Mild and Efficient Synthesis of Amino-Steroids

Abstract A number of steroids containing cyclic amino functions have been prepared and studied for biological activities, and some of them have proved to be clinically useful as a neuromuscular blocking agent, an antitumour agent, and so on.1 As the conventional methods, the reactions of cyclic amines with halides2 or epoxides,3 the reductive amination of ketones,4 and the reduction of enamines5 have been widely used for introducing these amino functions into steroid nucleus.