Crystal structure of 4,13-dimethyl-3,7,10,14,19,22,25-heptaoxapentacyclo- [25.0.0(1,6).0(6,26).0(11,16).0(11,18)]heptacosa-4,11-diene-2,15-dione.
of conjugated enones with olefins are useful for making a cyclobutane ring system. We have previously reported on the intermolecular photocycloaddition reactions of 2-pyrones with olefins,1–3 and the intramolecular photodimerization reactions of 4,4′-polymethylenedioxy-di-2-pyrones4 to clarify the reactivity involving the study of peri-, site, and stereoselectivities. As a part of an application of the cycloaddition reactions, we have planned to synthesize a macrocyclic compound possessing two cyclobutane rings using double photocycloaddition reactions of 6,6′-dimethyl-4,4′-dimethylenediox-di-2-pyrone (1) with di(ethylene glycol) divinyl ether (2). A solution of (1) (1.39 g), (2) (1.58 g), and xanthone (0.98 g) as a sensitizer in acetonitrile (500 ml) was irradiated with a 400W high-pressure mercury lamp (>350 nm ) for 20 h under a nitrogen atmosphere. After removing the solvent, an oily residue was chromatographed by silica gel (eluent: ethyl acetate–hexane) to give a solid product (3) in 20% yield, which was recrystallized from ethyl acetate. Since the usual analytical and spectroscopic techniques do not permit the identification of two types of isomers, (3) and (4) (in Fig. 1), an X-ray diffraction study of the product was carried out to determine the structure. Data collections were performed at 93 K with graphitemonochromated Mo Kα radiation on a Rigaku RAXIS-RAPID Imaging Plate diffractometer (λ = 0.71069 Å). Lorentz and polarization corrections were applied to the intensity data. The structure was solved by direct methods using SIR 92.5 The structure was refined by a full-matrix least-squares method. The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were refined isotropically. All calculations were performed using the teXsan6 crystallographic software package. Table 1 gives the crystal data and experimental conditions. Figure 2 is an ORTEP diagram of the molecule, which shows the atomic-labeling scheme. The final positional parameters are given in Table 2, and selected bond lengths and angles are listed in Table 3. 1017 ANALYTICAL SCIENCES AUGUST 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry
Species Specificity and Regio-selectivities in the Photocycloadditions of Cyclic Conjugated Enones and Heterocyclic Conjugated Dienones, and Their Frontier MO Analysis.
環状共役エノン類およびジエノン類の光付加環化における基質特異性と配向選択性等の現象を,PM3-CI法によるフロンティア分子軌道(FMO)法を用いて解析し,それらの支配要因を明らかにした。まず,2-ピロン類は,電子求引性または電子供与性アルケンと三重項反応を起こすが,その周辺([2+2]または[4+2]),位置(3,4-または5,6-付加)および配向(hhまたはht)選択性は,初期過程での位置·配向選択性を決める3-βまたは6-β間2中心FMO相互作用と,生成したビラジカル中間体のFMO作用による周辺選択的閉環反応に依存する。2-ピリドン類の電子求引性アルケンとの間の励起一重項または三重項での配向,位置および立体選択的[2+2]付加環化には,静電作用に加え前者で4中心のFMO作用,後者で2中心FMO作用が支配要因となる。これらのFMO法を最近問題となっている2-シクロヘキセノンや2-シクロペンテノン等のエノン体の環化反応の配向解析にも適用した。その三重項反応の配向選択性は主に初期過程のFMO作用に支配されるが,シクロペンテノンの場合ビラジカル中間体のFMOの影響が相対的に大きくht体を生成しやすくなると推定される。これら環状共役エノンとジエノンの光付加環化における基質特異性と配向位置および周辺選択性の関係がそのFMOの性質から説明できる。
THE IRON-ACETOCARMINE METHOD OF FIXING AND STAINING CHROMOSOMES
A short description of this procedure was given in Vol. 55 of the American Naturalist, pp. 573â€”574. The method has now been used almost daily for five years, and certain improvements have suggested themselves. The solution can be prepared by mixing about equal volumes of glacial acetic acid and water. To this is added powdered carmine in excess. The liquid is then â€ ? just brought to boil, cooled, and decanted. To the red solution there are then added a few drops of a solution of ferric hydrate in 50 per cent. acetic acid, to act as a mordant. The amount of iron varies with different objects. Too much produces a precipitate in a short time. The more