Yasuko Iizuka

Formation of cyclic organosilicon compounds via organopolysilyl anions starting from methoxymethyldisilanes. A mechanistic study

Abstract In the presence of a catalytic amount of sodium methoxide, sym -dimethoxytetramethyldisilane was converted into α,ω-dimethoxypermethylpolysilanes, MeO(SiMe 2 ) n OMe where n ⩾ 3, at room temperature. On the other hand, similar treatment of the disilane in THF solution gave cyclic polysilanes, (Me 2 Si) n where n = 5–7. Decomposition of the disilane in the presence of diphenylacetylene afforded a trisilacyclopentene derivative under similar conditions. This compound was obtained also by the reaction between α,ω-dimethoxypermethylpolysilanes and diphenylacetylene in the presence of sodium methoxide. These cyclic products most likely were formed via permethyl polysilyl anion intermediates derived from α,ω-dimethoxypermethylpolysilanes. Also, the formation of α,ω-dimethoxypermethylpolysilanes could be elucidated in terms of the mechanism involving the base-assisted, concerted nucleophilic substitution or stepwise substitution by silyl anions, rather than the successive dimethylsilylene (Me 2 Si:) insertion reaction.

Preparation and properties of copoly(n-hydroxyalkyl-d,l-glutamine) membranes

Abstract Random copolypeptide (PHADLG) membranes consisting of N-hydroxyalkyl- d -glutamine (HADG) and N-hydroxylalkyl- l -glutamine (HALG) covering the whole range of d,l -copolymer composition were prepared by carrying out aminolysis reactions with 3-amino-1-propanol (P) or 5-amino-1-pentanol (Pe), together with a crosslinking reaction with 1,8-octamethylenediamine (OMDA) on membranes of the starting random copolymers (PBDLG) consisting of γ-benzyl- d -glutamate and γ-benzyl- l -glutamate. The relationships between their bulk structure and membrane properties were investigated, such as the swelling ratio in water, tensile properties, water vapour permeability, and enzymatic degradation behaviour of the membranes in a pseudo-extracellular fluid (PECF), as a function of d,l -copolymer composition. The tensile properties of d,l -copolymer membranes were highly dependent on the swelling ratio of PECF. Biodegradation of these membranes in vitro by papain indicated that degradation was a bulk rather than a surface phenomenon, and that the rate of degradation of membranes was also highly dependent on the hydrophobicity of side chains, d,l -copolymer composition as well as on the swelling ratios of the d,l -copolymer samples.

Characterization of L-methionine in a peptide α-helix by far-infrared spectroscopy. Synthesis and examination of sequential polypeptides containing L-methionine

Sequential polypeptides containing L-methionine, viz.(Met-Ala-Ala)n, (Met-Met-Ala-Ala)n, (Met-Met-Ala)n, (Leu-Met-Leu)n, (Leu-Met-Met-Leu)n, and (Met-Met-Leu)n, were synthesized by polycondensation of peptide ONSu esters with corresponding sequences of amino acids; the ONSu esters were prepared stepwise by the method for peptide synthesis using Nps-amino acids and dicyclohexylcarbodi-imide. α-Helical samples of all the polypeptides showed a common far-i.r. band at 409 cm–1, the strength of which changed with the proportion of L-methionine residue in the polypeptides. Thus, this band was assigned to L-methionine in an α-helical polypeptide.

Adsorption of Organic Posphorous Insecticides and Herbicides by Polyamino Acids.

Recently, it have been reported that many clinical cases have injested insecticides and herbicides either for the purpose of suicide or by mistake, and thet these agricaltural chemicals poison the soil, especially rivers or lakes. Removal of these compounds is thus needed. In this regard, we report herein the application of polyamino acids for the adsorption of these agricultural chemicals by using the quartz-crystal microbalance (QCM) method.The homopolyamino acids exhigbit a high affinity to malathion. Poly (Leu) adsorbed an equal mass of cyanophos and trifluralin. Accordingly, polyamino acids are expected to be useful as adsorbents for organic phosphorous insecticides and herbicides.

Conformational Transition of Copolypeptides with both Hydrophilic and Hydrophobic Groups Side Chains.

側鎖に塩基性親水基を持つリジソ,オルニチソと疎水性基をもつアラニン,α -アミノ酪酸,さらにヒドロキシル基を持つセリンとのコポリペプチドを合成し,各種緩衝液中でpHおよび共存イオンのポリペプチドの二次構造に与える影響を,円偏光二色性スペクトルを用いて検討した.また,ポリリジンPoly(Lys)とも比較検討した.リジン-アラニン共重合体Poly(Lys,Ala)はクエン酸ナトリウム緩衝液中(pH4.53)でらせん(ヘリックス)構造をとるのに対し,塩化カリウム系(pH6.25)ではコイル状であった.また,リン酸緩衝液(pH6.86)ではPoly(Lys,Ala)共重合体はヘリックス構造をとるのに対しPoly(Lys)はコイル状であった.また,Poly(Lys,Ser)はヘリックス構造をとりにくいなど,ポリペプチドの二次構造は,溶液中の陰イオンの種類と構成するアミノ酸の種類に大きく依存した.側鎖にカルボキシル基とメチル基を有するアスパラギン酸-アラニン共重合体についても合わせて検討を行った.

Adsorption of Insecticides and Herbicides by Polymers.

有機リン系殺虫剤のスミチオン乳剤(フェニトロチナン,O, O-dimethyl O-4-nitro-m-tolyl phosphorothioate, 50%含有),カルホス乳剤(イソキサチオン, O, O-diethyl O-(5-pheny1-3-isoxazolyl) phosphorothioate, 50%含有),除草剤としてジニトロアニリン系のトレファノサイド乳剤(トリフルラリン,α,α,α-trifluoro-2, 6-dinitro-N, N-dipropyl-p-toluidine, 45%含有),アニリン系のクサノンA乳剤(プロパニル,3, 4-dichloropropionanilide, 25%,カーバリル,l-naphthyl N-methy1carbamate, 5%含有)を人工胃液,人工腸液,生理的食塩水で一定濃度に希釈し,その状態で殺虫剤,除草剤のポリアミノ酸に対する吸着性について検討した.その結果高分子量ポリ-L-ロイシンの人工胃液,人工腸液中でのフェニトロチオンに対する吸着性はアドソルビンに比較して優れていた.またポリアミノ酸の溶液中における吸着力は共存するヘパリンによって妨げられることはなかった.さらに人工胃液中では,ポリ-L-ロイシンにいったん吸着したフェニトロチオンは共存するヘパリンによって脱着されることもなかった. 本研究に有効な御助言をいただいた味の素株式会社岩月誠氏,筑波大学付属病院救急部長由下衛氏に感謝の意を表する.