Simultaneous assay of four stereoisomers of diltiazem hydrochloride. Application to in vitro chiral inversion studies

Summary The simultaneous stereospecific assay of four stereoisomers of diltiazem hydrochloride in bulk drug and aqueous solution was developed using HPLC on a Chiralcel OF column. The four isomers were quantitated with good precision by the internal standard method. The chiral inversion of (+)-cis-diltiazem hydrochloride in vitro, stability of its (2S, 3S) configuration in the solid and aqueous states was examined by HPLC. Chiral inversion of (+)-cis-diltiazem hydrochloride was not observed in the solid state, and its (2S, 3S) configuration was stable to heat, humidity and light. Chiral inversion of (+)-cis-diltiazem hydrochloride (2S, 3S) was observed in aqueous solution under UV, but not in aqueous solution stored at 80°C for 5 h nor under visible light for 10 h. The (+)-cis-diltiazem hydrochloride (2S, 3S) epimerized to (+)-trans-diltiazem hydrochloride (2R, 3S) with a half-life of 5 h in aqueous solution under UV but the reverse chiral inversion of (+)-trans-diltiazem hydrochloride (2R, 3S) to (+)-cis-diltiazem hydrochloride (2S, 3S) was not observed.     

固体^1^3C NMR研究呋喃醇和呋喃醇与三-(2-羟乙基)-异氰酸尿酯缩聚磺化反应

用固体^1^3C NMR研究了呋喃醇(FA)和FA与三-(2-羟乙基)-异氰酸尿酯(THEIC)缩聚磺化反应及其产物结构, 考察了2-甲基呋喃封端的FA线型齐聚物与甲醛水溶液在相转移催化剂(C~4H~9)~4N^+I^-和与大量硫酸作用下的反应特点, 探讨了主要参数对反应的影响。阐明了缩聚交联磺化反应的规律, 确定了产物的结构。     

α’-苯磺酰基-α，β-不饱和酮与开链二烯烃的不对称催化环加成反应

在手性金属钛催化剂存在下，研究了α’—苯磺酰基—α，β-不饱和酮与开 链二烯的不对称催化环加成反应，讨论了α’—苯磺酰基—α，β—不饱和酮与开 链二烯的反应活性和对映选择性，以高的收率和光学纯度合成了环己烯衍生物，并 对部分产物的构型进行了鉴定．     

垮越临界温度的分子筛吸附: 微孔体积填充理论的适用性

用高真空重量法测定了NaX分子筛对不同吸附质NH3, H2O, C2H5OH等的吸附等温线, 用微孔体积填充理论对吸附等温线进行非线性拟合, 得到满意结果。表明该理论不但可扩展到以静电场为主的吸附体系, 还可适用于吸附温度高于吸附质临界温度的吸附体系。计算结果表明, NaX吸附不同吸附质测得的极限空腔体积基本相同, 且与结构分析得到的空腔体积一致, 进一步表明微孔体积填充理论对该体系的适用性。计算了各种吸附质的极限吸附量, 以及某填充度下的蚊分吸附热随着温度的变化趋势。可为固体吸附式制冷系统的设计与制造提供理论依据及有关掺数。     

Some Extremal Properties of Section Spaces of Banach Bundles and Their Duals,II

Let π : E → X be a real Banach bundle with section space Γ(π), where X is a compact Hausdorff space. We complete the characterization of weak-* and sequential weak-* points of continuity in the unit ball of Γ(π) ? for certain classes of bundles (which include the trivial ones), which was begun in an earlier paper. The proofs avoid the use of vector measures.     

Killing Pairs in Flat Space

In this paper the integrability conditions for Killing pairs in flat spaces are investigated and it is shown that only trivial Killing pairs exist.     

Activation and Facile Dealkylation of Monooxides of 1,8-Bis(alkylthio)naphthalene and 2,2′-Bis(alkylthio)biphenyl with Triflic Anhydride via Dithiadications

Abstract

Dithiadications bearing 1,8-bis(alkylthio)naphthalene 2A(a-e) and 2,2′-bis(alkylthio)biphenyl 2B(a-e) structure undergo either the facile deprotonation from the methyl group or dealkylation from the methylene groups by the triflate anion. Dications 2A(a) and 2B(a) having methyl groups were deprotonated readily to afford cyclic sulfonium salts 3A(a) and 3B(a). However, dithiadications 2A(b-e) and 2B(b-e) having ethyl, propyl, isopropyl and benzyl groups were readily dealkylated even at -45°C to give thiasulfonium salts 4A(b-e) and 4B(b-e) and alkyl triflates 5(a-e) in good yields. The intermediary formation of dithiadications 2A(a-e) and 2B(a-e) were confirmed by direct observation using NMR spectroscopy, D-labelled experiments and trapping experiments.     

Letter: A Potential for the Lanczos Spintensor in Kerr Geometry

We show a generator of the Lanczos spintensorfor a rotating black hole.     

On the Geometry of Generalized Robertson-Walker Spacetimes: Geodesics

The geometry and, especially, the geodesics of a class of spacetimes generalizing Robertson-Walker ones (without any assumption on the fiber) is studied, under a global point of view. Our study covers geodesic connectedness, geodesic completeness and stability of completeness.     

Gravity as a Source of Phase Transitions

After going through several distinguished examples, we argue that gravity is definitely a source of phase transitions of quite different nature: usual scalar effective potential ones, chiral symmetry transitions and even transitions involving the chromomagnetic vacuum. In such context, we emphasize the fact that curvature-induced phase transitions of those kinds—where an interplay between general relativity and elementary particle physics occurs—can be used in the construction of new models of the inflationary universe.