Synthesis and Isolation of Regiospecific Mono Iodo-Cyclodextrin as a Fragile Intermediate to Amino-Cyclodextrin

lodo-CD (II) was prepared from toluenesulfonyl-CD (I) and purified by preparative HPLC. Iodo-CD (II) was easily converted to the amino-CD (III). Examination of the structure of the hydrolyzate from amino-CD (III) showed that indination and amination proceeded with inversion of configuration in both reactions

Permanent Electric Dipole-Dipole Interactions in Lyotropic Polypeptide Liquid Crystals

The interaction energy between two adjacent α-helical molecules was calculated taking into account for permanent electric dipoles locating orl the helical core of a polymer mainchain in order to explain the cholesteric structure of lyotropic polypeptide liquid crystals. It was concluded that the dipole-dipole interactions were responsible for the formation of the cholesteric structure

Enantioselective Peptide Synthesis by Using the Optically Active Polymer Containing the 1-Benzyl-3-Hydroxy-5-Isobutyl-Hydantoin Structure

The polymer containing the 1-benzyl-3-hydroxyhydantoin structure was prepared from styrene and 1-chloromethylhydantotin in order to achieve not only the act as acyl activating polymeric ester but the selective reaction using the D, L-amino acid seter. For the enantioselective peptide senthesis, the 1-benzyl-3-hydroxyhydantoin as a model compound and the 1-bernzyl-3-hydroxyhydantoin type polymer were allowed to act by two methods-the active ester method and the additive method using N, N\u27-dicyclohexylcarbodiimide (DCC). Optical yield was appreciated in 45%

Physical Properties of Non-Stoichiometric Sintered TiO Ceramics

Non-stoichiometric sintered TiO ceramics were produced by sintering at 1350℃ in a vacuum of 10^ Torr, starting from the mixed Powder of titanium oxide and titanium as raw materials. The TiO phase obtained was mainly cubic, but it contained complex ordered lattice structure phase only a little in the como position range between TiO_ and TiOi_. Some physical properties, such as mechanical, electrical and optical properties, and some factors governing the microstructure of the sintered bodies, such as mean crystal size, lattice strain and apparent density, were measured and related with the composition of non-stoichiometric TiO phase

Acetohydroxamic Acid for Peptide Synthesis

The ester derivatives of acetohydroxamic acid md N, N-diacetyl hydroxylamine, N, O-diacetyl hydroxylamine and triacetyl hydroxylamine were assured to be capable of being used as activated esters. At first, evaluation of acyl activating ability was made by reacting the above compounds with amine, and it was shown that all of them worked to yield amides with excellent conversion and that, among them, triacetyy hydroxylamine was most powerfull, where acetylation of amines went through its imide carbonyl group. Furthemore, dipeptide synthesis was found to accomplish without any racemization and in a good yield by use of acetohydroxamic acid. Next syntheses of polymers containing hydroxamic acid structure were carried out by the following routes. (a) methyl methacrylate was copolymerized with N-methacrylobenzyloxyamine and the copolymer obtained was debenzylated, (b) N-methacrylo-N, O-diacetyl hydroxylamine was polymerized, followed by hydrolysis and copolymers with styrene or methyl methacrylate were deacylated. The polymer obtained by route (a) was converted to the activated polymer ester of N-blocked diglycine and removal of the protecting group would provide a method for preparation of cyclic diglycine

Hydrolytic Catalysis with Complexation by Modified Cyclodextrins Having Diastereomeric Structure

At the presence of three regiospecifically modified cyclodextrins, i. e., β-CD-D-histidine (I_D), β-CD-L-histidine (I_L) and β-CD-histamine (III), the ester cleavage at neutral pH was compared concerning in enantiomeric selectivity as well as rate enhancement. Micha-elis-Menten-type kinetics were observed for I_D and I_L in the phenol release of acetylanyl (and phenylalanyl) p-nitrophenyl ester enantiomers. Second order rate constants were obtained for III. Stereochemical comparisons of the spatial geometry in the complexes were discussed and also the schematic scheme of the host-guest fit was discussed

Selective Cross-Acyloin Condensation Catalyzed by Thiazolium Salt II Selective Formation of 1-Hydroxy-2-ones form Formaldehyde and a Variety of Other Aldehydes, and a Proposal for the Possible Mechanism

The selective cross-acyloin condensation, where 1-hydroxy-2-ones were obtained selectively from formaldehyde and a wide variety of other aldehydes, was achieved by using 3-ethylbenzothiazolium bromide as a catalyst in the presence of triethylamine. The present reaction is expected to afford a novel and facile method for the synthesis of 1-hydroxy-2-ones. A mechanism accounting for the selective formation of 1-hydroxy-2-one was proposed based on the results obtained by examining the reactions between formaldehyde and P-substituted benzaldehydes. It is of much interest in the mechanism that two catalytic species show an inverse selectivity toward aldehydes

Polymers Having Stable Radicals : Electrochemical and Chemical Behaviors of the Polymer Having Nitroxyls.

As a part of this series on polymers having stable radicals, evaluation of oxidation-reduction potentials by polarography and oxidative reactivities toward hydrazine and hydrazobenzene has been dealt with on nitroxyl stable radicals. Poly (4-methacryloyloxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl) (III) as a polymer having stable radicals, and its prototypes, 4-oxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl (I) and 4-isobutyroyloxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl (II), have been employed for purpose of the study. The electrode reactions of (I) in a range of pH. 8.0-10.1 in aqueous media were observed to be quasi-reversible and the reduction half-wave potentials (E_) being between 0.120-0.200 V (vs. SCE) depending on pH.. In the other pH. regions, the reactions seemed to be irreversible and the reduction halfwave potentials depended uPon pH. as well. In addition, polarographic data in a non-aqueous medium ensured that all the nitroxyls (I), (II) and (III) might have the same redox potential values. The oxidation reactions, using (I), (II), and (III), on hydrazine and hydrazobenzene have been performed, of which extent was pursued spectrophotometrically. From the kinetics, it was elucidated that, (1) the reactions were bimolecula, (2) the rate determinant steps were in the first hydrogen abstraction and, (3) the reactions with hydrazine were reaction controlled (ΔE ; 11.2-11.3 Kcal/mol) while the reactions with hydrazobenzene were diffusion controlled (ΔE ; 5.9-3.9 Kcal/mol). Thermodynamic analysis indicated that the case of reaction with hydrazobenzene differed mechanistically whether the reactant was monomeric (II)or polymeric (III) (ΔS^‡ : -17.9 e. u., (II) ; -21.8 e.u., (III), at 20℃ in THF)and that a steric hindrance presumably took place in the latter